how to have limit switches reverse motor direction

K

krem

Guest
Hello, I have a motor lifting an object over a set range. Upon reaching a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again. I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible. (temperary on) The motor which needs
to be controlled is going to be running on either 5-6 volt dc supply and
doesn't pull a huge current. (typically runs on 4 AA batteries and lasts a
long time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance for any
input or suggestions
 
krem wrote:
Hello, I have a motor lifting an object over a set range. Upon reaching a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again. I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible. (temperary on) The motor which needs
to be controlled is going to be running on either 5-6 volt dc supply and
doesn't pull a huge current. (typically runs on 4 AA batteries and lasts a
long time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance for any
input or suggestions
Click to expand...
You need some device that remembers which switch was hit last. This
could be something as simple as a relay with extra sets of contacts.
If you want the motor to cycle continuously, you need at least a 3
pole double throw relay. Two of the contact sets connect the motor to
the power source so that the motor runs one way with the relay
energized, and the other way with the relay de-energized. Connect
supply + to the normally open contact on one set, and the normally
closed on the second. Connect supply - to the reverse normally on and
normally closed contacts of those two sets. Connect the motor between
those two commons.

Now, you need one limit switch to turn the relay on and one to turn it
off, and the relay using one of its contacts to remember which was
last.

The limit switch that turns the relay on must be normally open and
supply power to the coil. A third normally open contact parallels
this so the relay can keep itself energized after a pulse from this
switch.

The other switch has to be normally closed and is in series with the
above circuit. When it is bumped, it de-energized the coil, which
opens the contact that had been remembering that the relay was on.
Remembering to stay off takes no contacts.

--
John Popelish
 
John Popelish wrote:
krem wrote:

Hello, I have a motor lifting an object over a set range. Upon
reaching a set height i would like it to reverse and then start to
lower, and again once reaching a bottom position change direction
and begin to rase again. I know i'm going to have to end up using
limit switches and would prefer to use two push button ones if
possible. (temperary on) The motor which needs to be controlled is
going to be running on either 5-6 volt dc supply and doesn't pull a
huge current. (typically runs on 4 AA batteries and lasts a long
time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance
for any input or suggestions

You need some device that remembers which switch was hit last. This
could be something as simple as a relay with extra sets of contacts.
If you want the motor to cycle continuously, you need at least a 3
pole double throw relay. Two of the contact sets connect the motor to
the power source so that the motor runs one way with the relay
energized, and the other way with the relay de-energized. Connect
supply + to the normally open contact on one set, and the normally
closed on the second. Connect supply - to the reverse normally on and
normally closed contacts of those two sets. Connect the motor between
those two commons.

Now, you need one limit switch to turn the relay on and one to turn it
off, and the relay using one of its contacts to remember which was
last.

The limit switch that turns the relay on must be normally open and
supply power to the coil. A third normally open contact parallels
this so the relay can keep itself energized after a pulse from this
switch.

The other switch has to be normally closed and is in series with the
above circuit. When it is bumped, it de-energized the coil, which
opens the contact that had been remembering that the relay was on.
Remembering to stay off takes no contacts.
Click to expand...
If you go to the following web page and look at the bottom diagram,
The two push button switches can become limit switches.
The 240 volt motor becomes a DC one.
The two normally open relay contacts which switch power to the motor are changed to changeover contacts.
These are then used to reverse power to the motor when the limit switches are activated.
Hope that helps.

http://homepage.ntlworld.com/g.knott/elect129.htm
 
In message <6b76deee507e996a65edcf754c600620@news.teranews.com>, krem
<news@rkremser.endjunk.com> writes
Hello, I have a motor lifting an object over a set range. Upon reaching a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again. I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible.
Click to expand...
Of course it's possible to use momentary switches, but you need some
form of memory as stated elsewhere. A single changeover toggle switch
with the appropriate mechanical linkages to switch it at the top and
bottom of travel might be a lot easier for you. Clunk at the top to
reverse the motor, and click at the bottom to initiate
unreversalization.

--
Syd Rumpo
 
On Mon, 19 Apr 2004 07:56:39 GMT, "krem" <news@rkremser.endjunk.com>
wrote:

Hello, I have a motor lifting an object over a set range. Upon reaching a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again. I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible. (temperary on) The motor which needs
to be controlled is going to be running on either 5-6 volt dc supply and
doesn't pull a huge current. (typically runs on 4 AA batteries and lasts a
long time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance for any
input or suggestions
Click to expand...
---
Check alt.binaries.schematics.electronic under

"How to have limit switches reverse motor direction" or click on:

9k1880huvd6pgh3t2ulfcaamt510b6ntui@4ax.com

--
John Fields
 
On Mon, 19 Apr 2004 12:10:32 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Mon, 19 Apr 2004 07:56:39 GMT, "krem" <news@rkremser.endjunk.com
wrote:

Hello, I have a motor lifting an object over a set range. Upon reaching a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again. I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible. (temperary on) The motor which needs
to be controlled is going to be running on either 5-6 volt dc supply and
doesn't pull a huge current. (typically runs on 4 AA batteries and lasts a
long time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance for any
input or suggestions

---
Check alt.binaries.schematics.electronic under

"How to have limit switches reverse motor direction" or click on:

9k1880huvd6pgh3t2ulfcaamt510b6ntui@4ax.com
Click to expand...
---
Oops...

jn1880tarnmnjg1f2lg4gr7ru0reeuhep5@4ax.com

for the picture, duhhh...

--
John Fields
 
Hi Krem,

You could also use single contact switches and a flip-flop, even one made out of
a couple NAND gates. Then drive the motor with two push-pull transistor pairs
connected to that flip flop, which makes it a polarity reversing bridge, 5
volts. Or one of those National motor drivers chips in which case you may select
higher voltages. One thing to check out is how the start up is handled when this
"one bit" memory doesn't know what to do in case the motor happens to be in
between end positions. Maybe easy if the motor never leaves the range between
the two switches and you can send it to default down or something.

Regards, Joerg.
 
I was thinking of this but how would the top switch then reset and be ready
for another cycle. a mechanical linkage for that woudln't be possible in
the application.

"Syd Rumpo" <sydrumpox@clarat.co.uk> wrote in message
news:N9dA7kACq+gAFwY0@clara.co.uk...
In message <6b76deee507e996a65edcf754c600620@news.teranews.com>, krem
news@rkremser.endjunk.com> writes
Hello, I have a motor lifting an object over a set range. Upon reaching
a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again.
I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible.

Of course it's possible to use momentary switches, but you need some
form of memory as stated elsewhere. A single changeover toggle switch
with the appropriate mechanical linkages to switch it at the top and
bottom of travel might be a lot easier for you. Clunk at the top to
reverse the motor, and click at the bottom to initiate
unreversalization.

--
Syd Rumpo
Click to expand...
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:4083D752.AA464024@rica.net...
krem wrote:

Hello, I have a motor lifting an object over a set range. Upon reaching
a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase
again. I
know i'm going to have to end up using limit switches and would prefer
to
use two push button ones if possible. (temperary on) The motor which
needs
to be controlled is going to be running on either 5-6 volt dc supply
and
doesn't pull a huge current. (typically runs on 4 AA batteries and
lasts a
long time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance for
any
input or suggestions

You need some device that remembers which switch was hit last. This
could be something as simple as a relay with extra sets of contacts.
If you want the motor to cycle continuously, you need at least a 3
pole double throw relay. Two of the contact sets connect the motor to
the power source so that the motor runs one way with the relay
energized, and the other way with the relay de-energized. Connect
supply + to the normally open contact on one set, and the normally
closed on the second. Connect supply - to the reverse normally on and
normally closed contacts of those two sets. Connect the motor between
those two commons.

Now, you need one limit switch to turn the relay on and one to turn it
off, and the relay using one of its contacts to remember which was
last.

The limit switch that turns the relay on must be normally open and
supply power to the coil. A third normally open contact parallels
this so the relay can keep itself energized after a pulse from this
switch.

The other switch has to be normally closed and is in series with the
above circuit. When it is bumped, it de-energized the coil, which
opens the contact that had been remembering that the relay was on.
Remembering to stay off takes no contacts.

--
John Popelish
Click to expand...
Perfect, this was exactly what i was looking for. I knew a general
structure of what needed to be done but didn't think of using a single relay
to do it all. I'm off to throw one together and put it in. Thanks again.
 
On Mon, 19 Apr 2004 17:41:39 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hi Krem,

You could also use single contact switches and a flip-flop, even one made out of
a couple NAND gates. Then drive the motor with two push-pull transistor pairs
connected to that flip flop, which makes it a polarity reversing bridge, 5
volts. Or one of those National motor drivers chips in which case you may select
higher voltages. One thing to check out is how the start up is handled when this
"one bit" memory doesn't know what to do in case the motor happens to be in
between end positions. Maybe easy if the motor never leaves the range between
the two switches and you can send it to default down or something.
Click to expand...
---
As long as you've got the wiring right and you make sure that the
limit switches are momentary, it won't make any difference how the
motor starts up, it'll always reverse its direction as soon as it hits
either limit switch.

Also, if you're using a bipolar bridge you have to be careful to
isolate the bases from each other, but if you use something like an
HC00 you can drive all four bases separately as long as the motor
doesn't need a lot of current. Or, if it does, drive it with
Darlingtons if you have to go bipolar. I posted a MOSFET way to do it
to alt.binaries,schematics.electronic a little while ago, if you're
interested.

--
John Fields
 
krem wrote:
The motor which needs
to be controlled is going to be running on either 5-6 volt dc supply and
doesn't pull a huge current. (typically runs on 4 AA batteries and lasts a
long time)
Click to expand...
Aaah, an easy solution is to use a double pole relay, but you are going
to shorten your battery life as the relay has to be held on for one leg.

+ & - go to poles on one side and opposite poles on other side. Motor
power taps from central poles. Power on, say raises the motor.

Top limit switch energises and latches the relay (The relay can provide
power to itself once operated (diode off one leg of motor cable). So the
motor now runs in reverse.

bottom limit switch interupts the latching of relay, which releases and
motor goes up again.
 
Thanks for all the suggestions, the method using a three pole double throw
relay is working wonders, exactly what i needed and it was an easy solution.
Thanks again for all the inputs.

"krem" <news@rkremser.endjunk.com> wrote in message
news:6b76deee507e996a65edcf754c600620@news.teranews.com...
Hello, I have a motor lifting an object over a set range. Upon reaching a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again.
I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible. (temperary on) The motor which needs
to be controlled is going to be running on either 5-6 volt dc supply and
doesn't pull a huge current. (typically runs on 4 AA batteries and lasts
a
long time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance for
any
input or suggestions
Click to expand...
 
krem wrote:
Thanks for all the suggestions, the method using a three pole double throw
relay is working wonders, exactly what i needed and it was an easy solution.
Thanks again for all the inputs.
Click to expand...
Now you are ready for the subtleties. You may want to add a low value
series resistor to the motor, to reduce the current surge when a
reversal occurs. You may also want ot connect a pair of seriesed
zener diodes (one turned each way) rated for a little higher than your
supply voltage across the two common contacts that feed the motor, to
reduce contact arching when the motor reverses.

These details may increase the life if the relay contacts by a factor
of 10 (I don't know if that is important ot you).

--
John Popelish
 
John's suggestions remind me of when I blew up some relays with arcing
contacts...sealed in metal cans, so I didn't know at first what I was
doing to them! A bit higher current and voltage, and a very inductive
load...

Another comment for the lurkers or those who in the future find this
thread archived somewhere... If you try the same sort of thing with a
single-phase AC induction motor, it's very likely to keep running the
same direction when the stop is reached. They generally get their
"direction" information from the kick of the starter winding, which is
disconnected when the motor comes up to speed. If you don't slow the
motor down enough for the starter winding to become reconnected
between direction change commands, it'll probably just keep running
the same direction.

Cheers,
Tom

John Popelish <jpopelish@rica.net> wrote in message news:<4085AACA.F03D95B5@rica.net>...
krem wrote:

Thanks for all the suggestions, the method using a three pole double throw
relay is working wonders, exactly what i needed and it was an easy solution.
Thanks again for all the inputs.

Now you are ready for the subtleties. You may want to add a low value
series resistor to the motor, to reduce the current surge when a
reversal occurs. You may also want ot connect a pair of seriesed
zener diodes (one turned each way) rated for a little higher than your
supply voltage across the two common contacts that feed the motor, to
reduce contact arching when the motor reverses.

These details may increase the life if the relay contacts by a factor
of 10 (I don't know if that is important ot you).
Click to expand...
 
On Mon, 19 Apr 2004 18:06:25 GMT, "krem" <news@rkremser.endjunk.com>
wrote:

I was thinking of this but how would the top switch then reset and be ready
for another cycle. a mechanical linkage for that woudln't be possible in
the application.

"Syd Rumpo" <sydrumpox@clarat.co.uk> wrote in message
news:N9dA7kACq+gAFwY0@clara.co.uk...
In message <6b76deee507e996a65edcf754c600620@news.teranews.com>, krem
news@rkremser.endjunk.com> writes
Hello, I have a motor lifting an object over a set range. Upon reaching
a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again.
I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible.

Of course it's possible to use momentary switches, but you need some
form of memory as stated elsewhere. A single changeover toggle switch
with the appropriate mechanical linkages to switch it at the top and
bottom of travel might be a lot easier for you. Clunk at the top to
reverse the motor, and click at the bottom to initiate
unreversalization.

--
If the lifting and lowering distance isn't too great a simple crank
Click to expand...
would do the job. No need then to reverse the motor direction.

Al
2004 insult page awaits your contribution
http://kwakakid.cjb.net/insult.html
 
alb_mandctdNOWMD@connexus.net.au (Albm&ctd) wrote:

If the lifting and lowering distance isn't too great a simple crank
would do the job. No need then to reverse the motor direction.
Click to expand...
For a few months I've been contemplating using that approach for a
possible Tea Accelerator. I would attach a clip to the tea bag and a
mono would raise and lower it for say 2 mins then alert me to
completion. Optimising rate of crank rotation would be important to
eliminate wave build up. Major downside might be motor noise. I was
wondering if a solenoid could be operated in silent mode by suitable
signal?

--
Terry Pinnell
Hobbyist, West Sussex, UK
 
[Sorry if this eventually appears twice, but first attempt seems to
have vanished into net limbo. At least, can't see it here in Agent.]

====================
This naturally doesn't meet your requirement for constant unattended
operation. But it may be of interest to anyone who ends up here via
keywords like 'motor' and 'reversal'. Uses a 2-pole changeover relay
plus two N/C microswitches.
http://www.terrypin.dial.pipex.com/Images/AutoMotorExtremes.gif

I used it on a couple of projects, such as an automatic curtain
operator, and a window-operator. The latter (using a surplus
windscreen-wiper motor) would let me open the window after switching
off the bedside light.

Used it after reading, with window initially closed against
moths/bugs; avoided having to emerge from 'heavy eyelid mode'. Or
again in morning in heavy rain/wind. Its inherent 'locking' into the
extreme positions was a nice feature, but really strong winds
occasionally got the better of my primitive mechanics. Gave me years
of useful performance.

--
Terry Pinnell
Hobbyist, West Sussex, UK
 
Terry Pinnell wrote:
For a few months I've been contemplating using that approach for a
possible Tea Accelerator. I would attach a clip to the tea bag and a
mono would raise and lower it for say 2 mins then alert me to
completion. Optimising rate of crank rotation would be important to
eliminate wave build up. Major downside might be motor noise. I was
wondering if a solenoid could be operated in silent mode by suitable
signal?
Click to expand...
Sounds like a natural application for "muscle wire." Some mechanical linkage
would no doubt be required.

--
John Miller
Email address: domain, n4vu.com; username, jsm

The horror... the horror!
 
I read in sci.electronics.design that Albm&ctd <alb_mandctdNOWMD@connexu
s.net.au> wrote (in <40851333.2827208@news.individual.net>) about 'how
to have limit switches reverse motor direction', on Wed, 21 Apr 2004:

If the lifting and lowering distance isn't too great a simple crank
would do the job. No need then to reverse the motor direction.
Click to expand...
Maybe one of the many simple cranks we have on this NG would volunteer?
(;-)
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
 
krem wrote:
Hello, I have a motor lifting an object over a set range. Upon reaching a
set height i would like it to reverse and then start to lower, and again
once reaching a bottom position change direction and begin to rase again. I
know i'm going to have to end up using limit switches and would prefer to
use two push button ones if possible. (temperary on) The motor which needs
to be controlled is going to be running on either 5-6 volt dc supply and
doesn't pull a huge current. (typically runs on 4 AA batteries and lasts a
long time) I would like to have a solution which doesn't include and
microcontrollers as i've yet to take that plunge. Thanks in advance for any
input or suggestions
Click to expand...
Operate the motor through a DPDT switch set up to reverse its direction.
Then, mount the switch itself (via a flexible cable) or a means of
flipping the switch between its two positions on the moveable object.

--
Paul Hovnanian mailto:paul@Hovnanian.com
note to spammers: a Washington State resident
------------------------------------------------------------------
How do I set a laser printer to stun?
 
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