HIgh Current Mosfet Toggle noise issues?

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

 

[John Larkin]

On Sun, 21 Oct 2007 14:20:00 -0700, stan.portis@gmail.com wrote:

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

This works:

http://img20.imageshack.us/my.php?image=pushpushxo0.jpg

John

 

[Rich Grise]

On Sun, 21 Oct 2007 14:38:18 -0700, John Larkin wrote:

On Sun, 21 Oct 2007 14:20:00 -0700, stan.portis@gmail.com wrote:

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

This works:

http://img20.imageshack.us/my.php?image=pushpushxo0.jpg

I'd add, say, 1M from gate to Vss, so it comes up off.

Cheers!
Rich

 

[John Larkin]

On Sun, 21 Oct 2007 23:11:41 GMT, Rich Grise <rich@example.net> wrote:

On Sun, 21 Oct 2007 14:38:18 -0700, John Larkin wrote:
On Sun, 21 Oct 2007 14:20:00 -0700, stan.portis@gmail.com wrote:

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

This works:

http://img20.imageshack.us/my.php?image=pushpushxo0.jpg


I'd add, say, 1M from gate to Vss, so it comes up off.

Cheers!
Rich

But then it wouldn't toggle. The gate has to float.

John

 

[Hammy]

On Sun, 21 Oct 2007 14:20:00 -0700, stan.portis@gmail.com wrote:

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan
Do you have an RC snubber?

http://www.appliancedesign.com/CDA/Archives/f56a497a00dbc010VgnVCM100000f932a8c0____

 

[Jamie]

stan.portis@gmail.com wrote:

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

This is just a guess.

The L time constant on the relay coil is causing a Hi Z long enough to
allow the 10k RC via the diode to charge up enough for the power fet to
obtain enough bias to turn on before the coil in the relay saturates.

Maybe a low value non inductive resistor across the coil will help.
and also reduce the value of the .1 uf cap on the 3904 tranny.

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

 

[ehsjr]

stan.portis@gmail.com wrote:

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

Try modifying the original circuit by adding a diode and
a 470 uF cap, like this:

Original:
+Vcc
|
+----------+
| |
[10K] [Load]
| |
etc etc

Modified:

+Vcc
|
+-----+---|<----+
| | |
[10K] [470uF] [Load]
| | |
etc Gnd etc

 

[Jon Slaughter]

<stan.portis@gmail.com> wrote in message
news:1193001600.956543.96370@v29g2000prd.googlegroups.com...

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

(Repost cause first didn't show up)

A very simple debouncer might be something like

http://server6.theimagehosting.com/image.php?img=debounce.JPG


Its not the best and is asymmetric. R2 and R4 form a voltage divider when
the switch is closed and because of the way it is set up you'll need R4
about < R2/10. It depends on the gate threshold voltage though and you can
set up optimal components for different times. The time constants are about
R2*C1 and R2*C1/10 so you can choose C1 from the second(max switch settling
time < R2*C1/10)... noting that it forces the second time constant to be 10
times longer. This means if your switch needs more than 100ms then it will
require 1s.

This circuit isn't for a momentary switch though but could be modified by
adding a flip flip. Not sure if thats what your using. You can add a
pulldown to the gate which also will slowly
discharge the cap over time if no power is supplied.

The circuit could probably be improved but would require you to mess around
with the components to get the optimal result. (I don't know your supply
voltage or gate threshold voltage so I don't know what to choose for the
resistors). You could use something like a zener or other things to do a
better job but I tried to keep it a simple as possible.

You can offset the asymmetry somewhat and it will mainly just require a
zener or a few diodes. I can go into the theory more if your interested.

Basically though tC = R2*C1 and, say, tD = R4*C1 where tC = charge time, tD
= discharge time.

if tC = tD then R2*C1 = R4*C1 ==> R2 = R4. Problem here is that because R2
and R4 form a voltage divider you'll never discharge C1 enough in most cases
except if you limit the max voltage on the gate to be about 1 voltage above
its max. But then it might be somewhat unstable. (depending on how critical
the application one can improve on the circuit to make it symmetric so there
is no practical stability issues)

About your specific problem, I do not know what you mean by power to gate.
Also, a diode should not stop bounding on a DC relay. Seems like something
else might be going on there.

To main issues usually associated with relays are

http://en.wikipedia.org/wiki/Snubber

http://www.coilgun.info/theory/inductivekickback.htm

 

On Oct 22, 3:46 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:

stan.por...@gmail.com> wrote in message

news:1193001600.956543.96370@v29g2000prd.googlegroups.com...





Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

(Repost cause first didn't show up)

A very simple debouncer might be something like

http://server6.theimagehosting.com/image.php?img=debounce.JPG

Its not the best and is asymmetric. R2 and R4 form a voltage divider when
the switch is closed and because of the way it is set up you'll need R4
about < R2/10. It depends on the gate threshold voltage though and you can
set up optimal components for different times. The time constants are about
R2*C1 and R2*C1/10 so you can choose C1 from the second(max switch settling
time < R2*C1/10)... noting that it forces the second time constant to be 10
times longer. This means if your switch needs more than 100ms then it will
require 1s.

This circuit isn't for a momentary switch though but could be modified by
adding a flip flip. Not sure if thats what your using. You can add a
pulldown to the gate which also will slowly
discharge the cap over time if no power is supplied.

The circuit could probably be improved but would require you to mess around
with the components to get the optimal result. (I don't know your supply
voltage or gate threshold voltage so I don't know what to choose for the
resistors). You could use something like a zener or other things to do a
better job but I tried to keep it a simple as possible.

You can offset the asymmetry somewhat and it will mainly just require a
zener or a few diodes. I can go into the theory more if your interested.

Basically though tC = R2*C1 and, say, tD = R4*C1 where tC = charge time, tD
= discharge time.

if tC = tD then R2*C1 = R4*C1 ==> R2 = R4. Problem here is that because R2
and R4 form a voltage divider you'll never discharge C1 enough in most cases
except if you limit the max voltage on the gate to be about 1 voltage above
its max. But then it might be somewhat unstable. (depending on how critical
the application one can improve on the circuit to make it symmetric so there
is no practical stability issues)

About your specific problem, I do not know what you mean by power to gate.
Also, a diode should not stop bounding on a DC relay. Seems like something
else might be going on there.

To main issues usually associated with relays are

http://en.wikipedia.org/wiki/Snubber

http://www.coilgun.info/theory/inductivekickback.htm- Hide quoted text -

- Show quoted text

I added two relays. Each time I added one it caused the circuit to
not always latch the output closed, appearing to bounce the relay.
When I added the diode across the coils it took that away. But now
that I added the third and final relay which is 120vac coil I can't
add a diode across the coil (or can I since it's ac).

Also Vcc is about 18volts dc.

When I mentioned power to the gate, by that I mean when there is
voltage at the gate of my mosfet, the mosfet is turned on. When the
gate is close to zero, the mosfet is turned off. Turned off is the
condition I am looking for when I power this circuit up. I preferably
would like to stick with this circuit since it's built and already in
the box installed.

Thanks---

 

[Jon Slaughter]

<stan.portis@gmail.com> wrote in message
news:1193185980.969120.306620@z24g2000prh.googlegroups.com...

On Oct 22, 3:46 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:
stan.por...@gmail.com> wrote in message

news:1193001600.956543.96370@v29g2000prd.googlegroups.com...





Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

(Repost cause first didn't show up)

A very simple debouncer might be something like

http://server6.theimagehosting.com/image.php?img=debounce.JPG

Its not the best and is asymmetric. R2 and R4 form a voltage divider
when
the switch is closed and because of the way it is set up you'll need R4
about < R2/10. It depends on the gate threshold voltage though and you
can
set up optimal components for different times. The time constants are
about
R2*C1 and R2*C1/10 so you can choose C1 from the second(max switch
settling
time < R2*C1/10)... noting that it forces the second time constant to be
10
times longer. This means if your switch needs more than 100ms then it
will
require 1s.

This circuit isn't for a momentary switch though but could be modified by
adding a flip flip. Not sure if thats what your using. You can add a
pulldown to the gate which also will slowly
discharge the cap over time if no power is supplied.

The circuit could probably be improved but would require you to mess
around
with the components to get the optimal result. (I don't know your supply
voltage or gate threshold voltage so I don't know what to choose for the
resistors). You could use something like a zener or other things to do a
better job but I tried to keep it a simple as possible.

You can offset the asymmetry somewhat and it will mainly just require a
zener or a few diodes. I can go into the theory more if your interested.

Basically though tC = R2*C1 and, say, tD = R4*C1 where tC = charge time,
tD
= discharge time.

if tC = tD then R2*C1 = R4*C1 ==> R2 = R4. Problem here is that because
R2
and R4 form a voltage divider you'll never discharge C1 enough in most
cases
except if you limit the max voltage on the gate to be about 1 voltage
above
its max. But then it might be somewhat unstable. (depending on how
critical
the application one can improve on the circuit to make it symmetric so
there
is no practical stability issues)

About your specific problem, I do not know what you mean by power to
gate.
Also, a diode should not stop bounding on a DC relay. Seems like
something
else might be going on there.

To main issues usually associated with relays are

http://en.wikipedia.org/wiki/Snubber

http://www.coilgun.info/theory/inductivekickback.htm- Hide quoted text -

- Show quoted text

I added two relays. Each time I added one it caused the circuit to
not always latch the output closed, appearing to bounce the relay.
When I added the diode across the coils it took that away. But now
that I added the third and final relay which is 120vac coil I can't
add a diode across the coil (or can I since it's ac).

No diode on AC because then you supply DC current to the load through the
diode regardless of the state of the relay. You'll need a snubber over your
load and relay.

I'm not sure how complex your circuit is but you might need to troubleshoot
some and figure out where the problem is. Try using some led's and resistors
for your loads to see if the load is the problem or if its the switching.

Theres several problems that could be happening. Your switches could still
be bouncing because you didn't choose the time constant properly. The relays
could be bouncing to due to some type of oscillation that the switching
circuit is having. There could be some inductive kickback working its way to
the DC relays causing them problems(and hence why the diodes work).

It sounds like the problem is probably inductive kickback though but it
could be a combination. Try putting diodes on the DC relay's and an RC
snubber on the AC relay. (Although why do you need an AC relay to switch
something on when you can use a dc relay since you already have the DC
setup)?

You realize that AC relays take AC current to switch it on and off but both
AC and DC can switch AC current.

It sounds as if you have a DC relay controlling a DC relay which controls an
AC relay which controls a motor.... but why not just control the motor with
a DC relay directly?

Also, make sure you are using the right type of relay for the job,

http://en.wikipedia.org/wiki/Relay

Also, from wiki,

"Alternatively a contact protection network, consisting of a capacitor and
resistor in series, may absorb the surge. If the coil is designed to be
energized with AC, a small copper ring can be crimped to the end of the
solenoid. This "shading ring" creates a small out-of-phase current, which
increases the minimum pull on the armature during the AC cycle."

Also Vcc is about 18volts dc.

When I mentioned power to the gate, by that I mean when there is
voltage at the gate of my mosfet, the mosfet is turned on. When the
gate is close to zero, the mosfet is turned off. Turned off is the
condition I am looking for when I power this circuit up. I preferably
would like to stick with this circuit since it's built and already in
the box installed.

Easiest way here is to get a switch that has the opposite normal state than
the one your using.

You could exchange the BJT and 10k resistor positions and that should work
as it inverts the voltage states to the mosfet but if you already put
everything to gether it might be more work.

Jon

 

On Oct 24, 7:20 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:

stan.por...@gmail.com> wrote in message

news:1193185980.969120.306620@z24g2000prh.googlegroups.com...





On Oct 22, 3:46 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:
stan.por...@gmail.com> wrote in message

news:1193001600.956543.96370@v29g2000prd.googlegroups.com...

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

(Repost cause first didn't show up)

A very simple debouncer might be something like

http://server6.theimagehosting.com/image.php?img=debounce.JPG

Its not the best and is asymmetric. R2 and R4 form a voltage divider
when
the switch is closed and because of the way it is set up you'll need R4
about < R2/10. It depends on the gate threshold voltage though and you
can
set up optimal components for different times. The time constants are
about
R2*C1 and R2*C1/10 so you can choose C1 from the second(max switch
settling
time < R2*C1/10)... noting that it forces the second time constant to be
10
times longer. This means if your switch needs more than 100ms then it
will
require 1s.

This circuit isn't for a momentary switch though but could be modified by
adding a flip flip. Not sure if thats what your using. You can add a
pulldown to the gate which also will slowly
discharge the cap over time if no power is supplied.

The circuit could probably be improved but would require you to mess
around
with the components to get the optimal result. (I don't know your supply
voltage or gate threshold voltage so I don't know what to choose for the
resistors). You could use something like a zener or other things to do a
better job but I tried to keep it a simple as possible.

You can offset the asymmetry somewhat and it will mainly just require a
zener or a few diodes. I can go into the theory more if your interested.

Basically though tC = R2*C1 and, say, tD = R4*C1 where tC = charge time,
tD
= discharge time.

if tC = tD then R2*C1 = R4*C1 ==> R2 = R4. Problem here is that because
R2
and R4 form a voltage divider you'll never discharge C1 enough in most
cases
except if you limit the max voltage on the gate to be about 1 voltage
above
its max. But then it might be somewhat unstable. (depending on how
critical
the application one can improve on the circuit to make it symmetric so
there
is no practical stability issues)

About your specific problem, I do not know what you mean by power to
gate.
Also, a diode should not stop bounding on a DC relay. Seems like
something
else might be going on there.

To main issues usually associated with relays are

http://en.wikipedia.org/wiki/Snubber

http://www.coilgun.info/theory/inductivekickback.htm-Hide quoted text -

- Show quoted text

I added two relays. Each time I added one it caused the circuit to
not always latch the output closed, appearing to bounce the relay.
When I added the diode across the coils it took that away. But now
that I added the third and final relay which is 120vac coil I can't
add a diode across the coil (or can I since it's ac).

No diode on AC because then you supply DC current to the load through the
diode regardless of the state of the relay. You'll need a snubber over your
load and relay.

I'm not sure how complex your circuit is but you might need to troubleshoot
some and figure out where the problem is. Try using some led's and resistors
for your loads to see if the load is the problem or if its the switching.

Theres several problems that could be happening. Your switches could still
be bouncing because you didn't choose the time constant properly. The relays
could be bouncing to due to some type of oscillation that the switching
circuit is having. There could be some inductive kickback working its way to
the DC relays causing them problems(and hence why the diodes work).

It sounds like the problem is probably inductive kickback though but it
could be a combination. Try putting diodes on the DC relay's and an RC
snubber on the AC relay. (Although why do you need an AC relay to switch
something on when you can use a dc relay since you already have the DC
setup)?

You realize that AC relays take AC current to switch it on and off but both
AC and DC can switch AC current.

It sounds as if you have a DC relay controlling a DC relay which controls an
AC relay which controls a motor.... but why not just control the motor with
a DC relay directly?

Also, make sure you are using the right type of relay for the job,

http://en.wikipedia.org/wiki/Relay

Also, from wiki,

"Alternatively a contact protection network, consisting of a capacitor and
resistor in series, may absorb the surge. If the coil is designed to be
energized with AC, a small copper ring can be crimped to the end of the
solenoid. This "shading ring" creates a small out-of-phase current, which
increases the minimum pull on the armature during the AC cycle."

Also Vcc is about 18volts dc.

When I mentioned power to the gate, by that I mean when there is
voltage at the gate of my mosfet, the mosfet is turned on. When the
gate is close to zero, the mosfet is turned off. Turned off is the
condition I am looking for when I power this circuit up. I preferably
would like to stick with this circuit since it's built and already in
the box installed.

Easiest way here is to get a switch that has the opposite normal state than
the one your using.

You could exchange the BJT and 10k resistor positions and that should work
as it inverts the voltage states to the mosfet but if you already put
everything to gether it might be more work.

Jon- Hide quoted text -

- Show quoted text -

I did some testing. But first let me clarify what I am trying to do.
I am trying to control a woodworking dust collection system that draws
120vac/11amps. Initially I didn't realize that it pulled more than
10amps and therefore I wound up with three relays. The first relay is
a very small pc board dc relay (mounted on the pc board). The second
is an external relay mounted in the case. It is a 10amp dc relay.
The final relay is a 35amp ac controlled relay. (120vac coil). I
found that if I disconnect the third relay everything works as planned
with no issues. When the third relays coil is connected to my 10amp
relay it causes the circuit to switch on and not switch off, or not
switch on unless I try it 4-5 times. That third relay is screwing
everything up. Funny enough about the rc snubber circuit, I don't
even have the load connected to the third relay yet. I am still bench
testing. But, that 35amp relay does make quite a thump when it pulls
in. That is why I figured something needed to be done to the coil
control voltage. Should I still connect an rc circuit? If so, what
size values for the resistor and capacitor? I calculated 12uF and
1ohm at 11amps (22.5uF/.7ohms at 15amps).

The other idea that I think Jon was suggesting is to eliminate the
second and third relay by purchasing an 18-24vdc controlled relay
capable of switching approx 15amps ac on it's contacts. Is that
correct?

 

[Jon Slaughter]

<stan.portis@gmail.com> wrote in message
news:1193283416.005810.50970@i13g2000prf.googlegroups.com...

On Oct 24, 7:20 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:
stan.por...@gmail.com> wrote in message

news:1193185980.969120.306620@z24g2000prh.googlegroups.com...





On Oct 22, 3:46 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:
stan.por...@gmail.com> wrote in message

news:1193001600.956543.96370@v29g2000prd.googlegroups.com...

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side
of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and
that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac
coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

(Repost cause first didn't show up)

A very simple debouncer might be something like

http://server6.theimagehosting.com/image.php?img=debounce.JPG

Its not the best and is asymmetric. R2 and R4 form a voltage divider
when
the switch is closed and because of the way it is set up you'll need
R4
about < R2/10. It depends on the gate threshold voltage though and
you
can
set up optimal components for different times. The time constants are
about
R2*C1 and R2*C1/10 so you can choose C1 from the second(max switch
settling
time < R2*C1/10)... noting that it forces the second time constant to
be
10
times longer. This means if your switch needs more than 100ms then it
will
require 1s.

This circuit isn't for a momentary switch though but could be modified
by
adding a flip flip. Not sure if thats what your using. You can add a
pulldown to the gate which also will slowly
discharge the cap over time if no power is supplied.

The circuit could probably be improved but would require you to mess
around
with the components to get the optimal result. (I don't know your
supply
voltage or gate threshold voltage so I don't know what to choose for
the
resistors). You could use something like a zener or other things to
do a
better job but I tried to keep it a simple as possible.

You can offset the asymmetry somewhat and it will mainly just require
a
zener or a few diodes. I can go into the theory more if your
interested.

Basically though tC = R2*C1 and, say, tD = R4*C1 where tC = charge
time,
tD
= discharge time.

if tC = tD then R2*C1 = R4*C1 ==> R2 = R4. Problem here is that
because
R2
and R4 form a voltage divider you'll never discharge C1 enough in most
cases
except if you limit the max voltage on the gate to be about 1 voltage
above
its max. But then it might be somewhat unstable. (depending on how
critical
the application one can improve on the circuit to make it symmetric so
there
is no practical stability issues)

About your specific problem, I do not know what you mean by power to
gate.
Also, a diode should not stop bounding on a DC relay. Seems like
something
else might be going on there.

To main issues usually associated with relays are

http://en.wikipedia.org/wiki/Snubber

http://www.coilgun.info/theory/inductivekickback.htm-Hide quoted text -

- Show quoted text

I added two relays. Each time I added one it caused the circuit to
not always latch the output closed, appearing to bounce the relay.
When I added the diode across the coils it took that away. But now
that I added the third and final relay which is 120vac coil I can't
add a diode across the coil (or can I since it's ac).

No diode on AC because then you supply DC current to the load through the
diode regardless of the state of the relay. You'll need a snubber over
your
load and relay.

I'm not sure how complex your circuit is but you might need to
troubleshoot
some and figure out where the problem is. Try using some led's and
resistors
for your loads to see if the load is the problem or if its the switching.

Theres several problems that could be happening. Your switches could
still
be bouncing because you didn't choose the time constant properly. The
relays
could be bouncing to due to some type of oscillation that the switching
circuit is having. There could be some inductive kickback working its way
to
the DC relays causing them problems(and hence why the diodes work).

It sounds like the problem is probably inductive kickback though but it
could be a combination. Try putting diodes on the DC relay's and an RC
snubber on the AC relay. (Although why do you need an AC relay to switch
something on when you can use a dc relay since you already have the DC
setup)?

You realize that AC relays take AC current to switch it on and off but
both
AC and DC can switch AC current.

It sounds as if you have a DC relay controlling a DC relay which controls
an
AC relay which controls a motor.... but why not just control the motor
with
a DC relay directly?

Also, make sure you are using the right type of relay for the job,

http://en.wikipedia.org/wiki/Relay

Also, from wiki,

"Alternatively a contact protection network, consisting of a capacitor
and
resistor in series, may absorb the surge. If the coil is designed to be
energized with AC, a small copper ring can be crimped to the end of the
solenoid. This "shading ring" creates a small out-of-phase current, which
increases the minimum pull on the armature during the AC cycle."

Also Vcc is about 18volts dc.

When I mentioned power to the gate, by that I mean when there is
voltage at the gate of my mosfet, the mosfet is turned on. When the
gate is close to zero, the mosfet is turned off. Turned off is the
condition I am looking for when I power this circuit up. I preferably
would like to stick with this circuit since it's built and already in
the box installed.

Easiest way here is to get a switch that has the opposite normal state
than
the one your using.

You could exchange the BJT and 10k resistor positions and that should
work
as it inverts the voltage states to the mosfet but if you already put
everything to gether it might be more work.

Jon- Hide quoted text -

- Show quoted text -

I did some testing. But first let me clarify what I am trying to do.
I am trying to control a woodworking dust collection system that draws
120vac/11amps. Initially I didn't realize that it pulled more than
10amps and therefore I wound up with three relays. The first relay is
a very small pc board dc relay (mounted on the pc board). The second
is an external relay mounted in the case. It is a 10amp dc relay.
The final relay is a 35amp ac controlled relay. (120vac coil). I
found that if I disconnect the third relay everything works as planned
with no issues. When the third relays coil is connected to my 10amp
relay it causes the circuit to switch on and not switch off, or not
switch on unless I try it 4-5 times. That third relay is screwing
everything up. Funny enough about the rc snubber circuit, I don't
even have the load connected to the third relay yet. I am still bench
testing. But, that 35amp relay does make quite a thump when it pulls
in. That is why I figured something needed to be done to the coil
control voltage. Should I still connect an rc circuit? If so, what
size values for the resistor and capacitor? I calculated 12uF and
1ohm at 11amps (22.5uF/.7ohms at 15amps).

So your first DC relay is controlling the second DC relay which controls the
AC relay? The second DC relay is actually letting in AC(most likely the
mains?) into the AC relay?

What are you putting on the coil of the AC Relay and whats its coil ratings?
I hope you are not putting DC on the AC Relay's coil?

The other idea that I think Jon was suggesting is to eliminate the
second and third relay by purchasing an 18-24vdc controlled relay
capable of switching approx 15amps ac on it's contacts. Is that
correct?

This is the easier solution.

A quick search, for example, gives

http://www.components.omron.com/components/web/PDFLIB.nsf/0/55902B3819EACFE385257201007DD574/$file/G5CA_0607.pdf

(not recommending this one but just showing and example)

In this case you can control it with just one relay.

 

On Oct 25, 7:52 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:

stan.por...@gmail.com> wrote in message

news:1193283416.005810.50970@i13g2000prf.googlegroups.com...





On Oct 24, 7:20 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:
stan.por...@gmail.com> wrote in message

news:1193185980.969120.306620@z24g2000prh.googlegroups.com...

On Oct 22, 3:46 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:
stan.por...@gmail.com> wrote in message

news:1193001600.956543.96370@v29g2000prd.googlegroups.com...

Hello,
I built a circuit from this link:
http://ourworld.compuserve.com/homepages/bill_bowden/page9.htm
entitled "High Current Mosfet toggle switch with debounced push
button. It worked perfectly on the breadboard. When I installed it
on a pcb board with an external switch (inside an enclosure) the
circuit now powers on active. In other words, the IR510 Mosfet has
power on the gate pin, which is not how I want it to work. Can
anybody suggest what values I might change the10k/10uF on left side
of
circuit to, to resolve this?

The other issue I have is with the load. I connected a relay (k1,
24vdc coil)to the load terminals and had what I will call debounce,
where the relay doesn't always close, but bounces. It may take
several times to activate it. I put a diode across the coil and
that
resolved that problem. But my final load is 120vac 11amps so I am
driving a much larger relay which we will call K2. K2 has 120vac
coil
and contacts. Now when K2 is in the circuit, I get the same issue.
Can I put a diode across the ac portion of the coil to control this
spike or bounce? If I remove K2, my problem is gone.

Thanks,
Stan

(Repost cause first didn't show up)

A very simple debouncer might be something like

http://server6.theimagehosting.com/image.php?img=debounce.JPG

Its not the best and is asymmetric. R2 and R4 form a voltage divider
when
the switch is closed and because of the way it is set up you'll need
R4
about < R2/10. It depends on the gate threshold voltage though and
you
can
set up optimal components for different times. The time constants are
about
R2*C1 and R2*C1/10 so you can choose C1 from the second(max switch
settling
time < R2*C1/10)... noting that it forces the second time constant to
be
10
times longer. This means if your switch needs more than 100ms then it
will
require 1s.

This circuit isn't for a momentary switch though but could be modified
by
adding a flip flip. Not sure if thats what your using. You can add a
pulldown to the gate which also will slowly
discharge the cap over time if no power is supplied.

The circuit could probably be improved but would require you to mess
around
with the components to get the optimal result. (I don't know your
supply
voltage or gate threshold voltage so I don't know what to choose for
the
resistors). You could use something like a zener or other things to
do a
better job but I tried to keep it a simple as possible.

You can offset the asymmetry somewhat and it will mainly just require
a
zener or a few diodes. I can go into the theory more if your
interested.

Basically though tC = R2*C1 and, say, tD = R4*C1 where tC = charge
time,
tD
= discharge time.

if tC = tD then R2*C1 = R4*C1 ==> R2 = R4. Problem here is that
because
R2
and R4 form a voltage divider you'll never discharge C1 enough in most
cases
except if you limit the max voltage on the gate to be about 1 voltage
above
its max. But then it might be somewhat unstable. (depending on how
critical
the application one can improve on the circuit to make it symmetric so
there
is no practical stability issues)

About your specific problem, I do not know what you mean by power to
gate.
Also, a diode should not stop bounding on a DC relay. Seems like
something
else might be going on there.

To main issues usually associated with relays are

http://en.wikipedia.org/wiki/Snubber

http://www.coilgun.info/theory/inductivekickback.htm-Hidequoted text -

- Show quoted text

I added two relays. Each time I added one it caused the circuit to
not always latch the output closed, appearing to bounce the relay.
When I added the diode across the coils it took that away. But now
that I added the third and final relay which is 120vac coil I can't
add a diode across the coil (or can I since it's ac).

No diode on AC because then you supply DC current to the load through the
diode regardless of the state of the relay. You'll need a snubber over
your
load and relay.

I'm not sure how complex your circuit is but you might need to
troubleshoot
some and figure out where the problem is. Try using some led's and
resistors
for your loads to see if the load is the problem or if its the switching.

Theres several problems that could be happening. Your switches could
still
be bouncing because you didn't choose the time constant properly. The
relays
could be bouncing to due to some type of oscillation that the switching
circuit is having. There could be some inductive kickback working its way
to
the DC relays causing them problems(and hence why the diodes work).

It sounds like the problem is probably inductive kickback though but it
could be a combination. Try putting diodes on the DC relay's and an RC
snubber on the AC relay. (Although why do you need an AC relay to switch
something on when you can use a dc relay since you already have the DC
setup)?

You realize that AC relays take AC current to switch it on and off but
both
AC and DC can switch AC current.

It sounds as if you have a DC relay controlling a DC relay which controls
an
AC relay which controls a motor.... but why not just control the motor
with
a DC relay directly?

Also, make sure you are using the right type of relay for the job,

http://en.wikipedia.org/wiki/Relay

Also, from wiki,

"Alternatively a contact protection network, consisting of a capacitor
and
resistor in series, may absorb the surge. If the coil is designed to be
energized with AC, a small copper ring can be crimped to the end of the
solenoid. This "shading ring" creates a small out-of-phase current, which
increases the minimum pull on the armature during the AC cycle."

Also Vcc is about 18volts dc.

When I mentioned power to the gate, by that I mean when there is
voltage at the gate of my mosfet, the mosfet is turned on. When the
gate is close to zero, the mosfet is turned off. Turned off is the
condition I am looking for when I power this circuit up. I preferably
would like to stick with this circuit since it's built and already in
the box installed.

Easiest way here is to get a switch that has the opposite normal state
than
the one your using.

You could exchange the BJT and 10k resistor positions and that should
work
as it inverts the voltage states to the mosfet but if you already put
everything to gether it might be more work.

Jon- Hide quoted text -

- Show quoted text -

I did some testing. But first let me clarify what I am trying to do.
I am trying to control a woodworking dust collection system that draws
120vac/11amps. Initially I didn't realize that it pulled more than
10amps and therefore I wound up with three relays. The first relay is
a very small pc board dc relay (mounted on the pc board). The second
is an external relay mounted in the case. It is a 10amp dc relay.
The final relay is a 35amp ac controlled relay. (120vac coil). I
found that if I disconnect the third relay everything works as planned
with no issues. When the third relays coil is connected to my 10amp
relay it causes the circuit to switch on and not switch off, or not
switch on unless I try it 4-5 times. That third relay is screwing
everything up. Funny enough about the rc snubber circuit, I don't
even have the load connected to the third relay yet. I am still bench
testing. But, that 35amp relay does make quite a thump when it pulls
in. That is why I figured something needed to be done to the coil
control voltage. Should I still connect an rc circuit? If so, what
size values for the resistor and capacitor? I calculated 12uF and
1ohm at 11amps (22.5uF/.7ohms at 15amps).

So your first DC relay is controlling the second DC relay which controls the
AC relay? The second DC relay is actually letting in AC(most likely the
mains?) into the AC relay?

What are you putting on the coil of the AC Relay and whats its coil ratings?
I hope you are not putting DC on the AC Relay's coil?

The other idea that I think Jon was suggesting is to eliminate the
second and third relay by purchasing an 18-24vdc controlled relay
capable of switching approx 15amps ac on it's contacts. Is that
correct?

This is the easier solution.

A quick search, for example, gives

http://www.components.omron.com/components/web/PDFLIB.nsf/0/55902B381...

(not recommending this one but just showing and example)

In this case you can control it with just one relay.- Hide quoted text -

- Show quoted text -

So your first DC relay is controlling the second DC relay which
controls the

AC relay? The second DC relay is actually letting in AC(most likely the
mains?) into the AC relay?
Yes. I was really trying to keep ac off of the pcb board.

What are you putting on the coil of the AC Relay and whats its coil
ratings?

I hope you are not putting DC on the AC Relay's coil?
I'm putting 120vac on the coil, switched in and out by the second

relay. The ac relay is a GE CR7CE 600vac max, 35amp relay. The Coil
only says 120vac/60hz. It is a big one! I salvaged it off of
something years ago. I looked for the spec sheet online but haven't
run across it. It is definetely the one that causes my troubles.
Without it things are perfect. I like your idea of the omron
electronic relay. I will price that out.

 

[Jon Slaughter]

So your first DC relay is controlling the second DC relay which
controls the
AC relay? The second DC relay is actually letting in AC(most likely the
mains?) into the AC relay?
Yes. I was really trying to keep ac off of the pcb board.

What are you putting on the coil of the AC Relay and whats its coil
ratings?
I hope you are not putting DC on the AC Relay's coil?
I'm putting 120vac on the coil, switched in and out by the second
relay. The ac relay is a GE CR7CE 600vac max, 35amp relay. The Coil
only says 120vac/60hz. It is a big one! I salvaged it off of
something years ago. I looked for the spec sheet online but haven't
run across it. It is definetely the one that causes my troubles.
Without it things are perfect. I like your idea of the omron
electronic relay. I will price that out.

Ok, if you want to keep it off the pcb then use a secondary smaller dc relay
or mosfet to control the coil of the main one.

Although your AC relay should work I suppose(although the fact that its AC
triggered complicates things unnecessarily but if thats all you got it
should work).

You might want to first test the relay if you can. Put the mains across coil
and some load across the switch like a lightbulb or two.


Mains ---SW--+ +---+--- light --- Mains
| |
Coil Switch
| |
Mains -------+ +---+------------- Mains

where SW is some type of switch that you can cut the mains to the relay
which should turn the light off. Of course it goes without saying that you
need to be careful when working with the mains.

Jon

 

On Oct 25, 11:45 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com>
wrote:

So your first DC relay is controlling the second DC relay which
controls the
AC relay? The second DC relay is actually letting in AC(most likely the
mains?) into the AC relay?
Yes. I was really trying to keep ac off of the pcb board.

What are you putting on the coil of the AC Relay and whats its coil
ratings?
I hope you are not putting DC on the AC Relay's coil?
I'm putting 120vac on the coil, switched in and out by the second
relay. The ac relay is a GE CR7CE 600vac max, 35amp relay. The Coil
only says 120vac/60hz. It is a big one! I salvaged it off of
something years ago. I looked for the spec sheet online but haven't
run across it. It is definetely the one that causes my troubles.
Without it things are perfect. I like your idea of the omron
electronic relay. I will price that out.

Ok, if you want to keep it off the pcb then use a secondary smaller dc relay
or mosfet to control the coil of the main one.

Although your AC relay should work I suppose(although the fact that its AC
triggered complicates things unnecessarily but if thats all you got it
should work).

You might want to first test the relay if you can. Put the mains across coil
and some load across the switch like a lightbulb or two.

Mains ---SW--+ +---+--- light --- Mains
| |
Coil Switch
| |
Mains -------+ +---+------------- Mains

where SW is some type of switch that you can cut the mains to the relay
which should turn the light off. Of course it goes without saying that you
need to be careful when working with the mains.

Jon- Hide quoted text -

- Show quoted text -

I ordered an electronic relay, 15amp 120vc contacts with 12vdc control
voltage. Cost $2.83. May have it by tommorrow. Thanks for your
help. I was also trying to use that large relay in case I ever
upgrade to a larger 220vac dust collector. This particular contactor
has three poles on it. Must just be too noisey?? Seems like there
must be some way to isolate. (Opto-isolaters ?) But, I also like
the idea of simplicity. I will be able to elimate all three relays
with this new one. I might need to put a resistor on the Vss since
its 18vdc and the new relay is 12dc. I posted a picture of the
circuit http://www.tisd.net/~stanp/

If you know of a better way to post schematics let me know. Its kind
of small.

 

[Jon Slaughter]

<stan.portis@gmail.com> wrote in message
news:1193351266.730403.140710@o38g2000hse.googlegroups.com...

On Oct 25, 11:45 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com
wrote:
So your first DC relay is controlling the second DC relay which
controls the
AC relay? The second DC relay is actually letting in AC(most likely
the
mains?) into the AC relay?
Yes. I was really trying to keep ac off of the pcb board.

What are you putting on the coil of the AC Relay and whats its coil
ratings?
I hope you are not putting DC on the AC Relay's coil?
I'm putting 120vac on the coil, switched in and out by the second
relay. The ac relay is a GE CR7CE 600vac max, 35amp relay. The Coil
only says 120vac/60hz. It is a big one! I salvaged it off of
something years ago. I looked for the spec sheet online but haven't
run across it. It is definetely the one that causes my troubles.
Without it things are perfect. I like your idea of the omron
electronic relay. I will price that out.

Ok, if you want to keep it off the pcb then use a secondary smaller dc
relay
or mosfet to control the coil of the main one.

Although your AC relay should work I suppose(although the fact that its
AC
triggered complicates things unnecessarily but if thats all you got it
should work).

You might want to first test the relay if you can. Put the mains across
coil
and some load across the switch like a lightbulb or two.

Mains ---SW--+ +---+--- light --- Mains
| |
Coil Switch
| |
Mains -------+ +---+------------- Mains

where SW is some type of switch that you can cut the mains to the relay
which should turn the light off. Of course it goes without saying that
you
need to be careful when working with the mains.

Jon- Hide quoted text -

- Show quoted text -

I ordered an electronic relay, 15amp 120vc contacts with 12vdc control
voltage. Cost $2.83. May have it by tommorrow. Thanks for your
help. I was also trying to use that large relay in case I ever
upgrade to a larger 220vac dust collector. This particular contactor
has three poles on it. Must just be too noisey?? Seems like there
must be some way to isolate. (Opto-isolaters ?) But, I also like
the idea of simplicity. I will be able to elimate all three relays
with this new one. I might need to put a resistor on the Vss since
its 18vdc and the new relay is 12dc. I posted a picture of the
circuit http://www.tisd.net/~stanp/

Yeah, it should simplify things a great deal. If you need to upgrade and the
relay cannot handle it then just get a new one and its pretty much just plug
and play.


Remember to put a snubber on that relay though or it will wear out.

If you put 18vdc on the new relay then it will draw an excess amount of
current and probably over heat and burn up unless you have good ventalation.
(it will probably work fine but shorten the life) A resistor would probably
work fine for your purpose but its not ideal. If the coil draws I amps at V
volts then that means it has an equivalent resistance of I/V ohms and
increasing the voltage effectively decreases the equivalent resistance so
you can make that up with a series resistor(make sure it can handle the
power). (a real relay doesn't have a constant effective resistance since it
depends on the current but it should be fine)

Also note that it would have probably been better to use a latching relay to
simulate a switch so that excess power isn't wasted in holding the relay
closed... I think that what your doing but its probably not much power(few
watts maybe) so no big deal. (using a latching relay would probably require
a new circuit though so...)

If you know of a better way to post schematics let me know. Its kind
of small.

I use

http://www.theimagehosting.com/

when I need it but there are many others too(search google for free image
hosting)

Jon

 

On Oct 25, 7:37 pm, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:

stan.por...@gmail.com> wrote in message

news:1193351266.730403.140710@o38g2000hse.googlegroups.com...





On Oct 25, 11:45 am, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com
wrote:
So your first DC relay is controlling the second DC relay which
controls the
AC relay? The second DC relay is actually letting in AC(most likely
the
mains?) into the AC relay?
Yes. I was really trying to keep ac off of the pcb board.

What are you putting on the coil of the AC Relay and whats its coil
ratings?
I hope you are not putting DC on the AC Relay's coil?
I'm putting 120vac on the coil, switched in and out by the second
relay. The ac relay is a GE CR7CE 600vac max, 35amp relay. The Coil
only says 120vac/60hz. It is a big one! I salvaged it off of
something years ago. I looked for the spec sheet online but haven't
run across it. It is definetely the one that causes my troubles.
Without it things are perfect. I like your idea of the omron
electronic relay. I will price that out.

Ok, if you want to keep it off the pcb then use a secondary smaller dc
relay
or mosfet to control the coil of the main one.

Although your AC relay should work I suppose(although the fact that its
AC
triggered complicates things unnecessarily but if thats all you got it
should work).

You might want to first test the relay if you can. Put the mains across
coil
and some load across the switch like a lightbulb or two.

Mains ---SW--+ +---+--- light --- Mains
| |
Coil Switch
| |
Mains -------+ +---+------------- Mains

where SW is some type of switch that you can cut the mains to the relay
which should turn the light off. Of course it goes without saying that
you
need to be careful when working with the mains.

Jon- Hide quoted text -

- Show quoted text -

I ordered an electronic relay, 15amp 120vc contacts with 12vdc control
voltage. Cost $2.83. May have it by tommorrow. Thanks for your
help. I was also trying to use that large relay in case I ever
upgrade to a larger 220vac dust collector. This particular contactor
has three poles on it. Must just be too noisey?? Seems like there
must be some way to isolate. (Opto-isolaters ?) But, I also like
the idea of simplicity. I will be able to elimate all three relays
with this new one. I might need to put a resistor on the Vss since
its 18vdc and the new relay is 12dc. I posted a picture of the
circuithttp://www.tisd.net/~stanp/

Yeah, it should simplify things a great deal. If you need to upgrade and the
relay cannot handle it then just get a new one and its pretty much just plug
and play.

Remember to put a snubber on that relay though or it will wear out.

If you put 18vdc on the new relay then it will draw an excess amount of
current and probably over heat and burn up unless you have good ventalation.
(it will probably work fine but shorten the life) A resistor would probably
work fine for your purpose but its not ideal. If the coil draws I amps at V
volts then that means it has an equivalent resistance of I/V ohms and
increasing the voltage effectively decreases the equivalent resistance so
you can make that up with a series resistor(make sure it can handle the
power). (a real relay doesn't have a constant effective resistance since it
depends on the current but it should be fine)

Also note that it would have probably been better to use a latching relay to
simulate a switch so that excess power isn't wasted in holding the relay
closed... I think that what your doing but its probably not much power(few
watts maybe) so no big deal. (using a latching relay would probably require
a new circuit though so...)

If you know of a better way to post schematics let me know. Its kind
of small.

I use

http://www.theimagehosting.com/

when I need it but there are many others too(search google for free image
hosting)

Jon- Hide quoted text -

- Show quoted text -

The solid-state relay worked perfect! I received it Friday in the
mail and installed it right away. It eliminated all of the relays and
solved the noise issue and the current capacity issue. The coil is
driven by 12volts dc and the contacts are rated at 120v/15amps. My
circuit pulls 11amps. I connected it to my dust collector and it
works just as planned. Thanks to everyone's contribution ! That
solid state relay costs $2.83.

Stan