Help with Simple circuit and relay

[ULB]

Can someone look this circuit over for me and let me know if it looks
ok, and if any changes are needed?

The design is just a simple control circuit for a rocket launcher.
After posting a few days ago on an amp question (very helpful), it
seems the switches I found can't handle the larger amps, so I figured
the best way was to use a relay. Am I correct in saying that?

Basically, 12 volt car battery is used for power source. Keylock
switch (momentary) in series with a push button switch (momentary).
Just looking for maximum amps. Can you tell me what size fuse(s) I
should use for this? Does this fit the bill? Thank you!

http://i360.photobucket.com/albums/oo49/stockburn/circuit.jpg

 

[Tom Biasi]

"ULB" <ultralightbackpacker@yahoo.com> wrote in message
news:11b18f6d-3eed-4a94-8b47-a6f642f9b3fc@m25g2000yqc.googlegroups.com...

Can someone look this circuit over for me and let me know if it looks
ok, and if any changes are needed?

The design is just a simple control circuit for a rocket launcher.
After posting a few days ago on an amp question (very helpful), it
seems the switches I found can't handle the larger amps, so I figured
the best way was to use a relay. Am I correct in saying that?

Basically, 12 volt car battery is used for power source. Keylock
switch (momentary) in series with a push button switch (momentary).
Just looking for maximum amps. Can you tell me what size fuse(s) I
should use for this? Does this fit the bill? Thank you!

http://i360.photobucket.com/albums/oo49/stockburn/circuit.jpg

The circuit will function. You really don't need two fuses, you can fuse the
pos. output to both the coil and the ignighter.
How many ignighters are you powering at one time?
I can't see a switch not handling one, even a NiCr ignighter.
You can fuse as high as the wire rating or the switch ratings, which ever is
lower.

Tom

 

[Jon Kirwan]

On Mon, 4 Jan 2010 12:27:43 -0800 (PST), ULB
<ultralightbackpacker@yahoo.com> wrote:

Can someone look this circuit over for me and let me know if it looks
ok, and if any changes are needed?

The design is just a simple control circuit for a rocket launcher.
After posting a few days ago on an amp question (very helpful), it
seems the switches I found can't handle the larger amps, so I figured
the best way was to use a relay. Am I correct in saying that?

Basically, 12 volt car battery is used for power source. Keylock
switch (momentary) in series with a push button switch (momentary).
Just looking for maximum amps. Can you tell me what size fuse(s) I
should use for this? Does this fit the bill? Thank you!

http://i360.photobucket.com/albums/oo49/stockburn/circuit.jpg

Now that you've written the purpose, do you know what your
rocket launcher's pyro requirements are?

Just as a possible aid, because I've been personally involved
in a different phase of my life:

If you are using the squibs used for the Estes-type engines,
I recall a conversation I had with their lead engineer more
than a decade back who told me that the experience 100%
success rates with the delivery of 3.1 amps for 50
milliseconds. Because this is a heating vs dissipation
issue, a higher pulse for shorter times should work. Their
final spec is for 3.75 amps for 50 milliseconds to provide a
safety margin over the all-fire value they experienced.

He also told me they don't have a maximum "no fire" spec, but
that 50 milliamps continuous is safe. They also observed no
ignitions using 700 milliamps for 50 milliseconds, but using
that level for longer will fire squibs, eventually. An
amount below the 50mA continuous figure can be used to verify
the existence of a complete circuit.

They chose the 50 millisecond period only because it was the
time they designed into their test-fire equipment, and not
for other reasons, according to that engineer.

For those considering specific recommendations, those are the
details I recall.

Jon

 

[ULB]

On Jan 4, 12:56 pm, "Tom Biasi" <tombi...@optonline.net> wrote:

"ULB" <ultralightbackpac...@yahoo.com> wrote in message

news:11b18f6d-3eed-4a94-8b47-a6f642f9b3fc@m25g2000yqc.googlegroups.com...

Can someone look this circuit over for me and let me know if it looks
ok, and if any changes are needed?

The design is just a simple control circuit for a rocket launcher.
After posting a few days ago on an amp question (very helpful), it
seems the switches I found can't handle the larger amps, so I figured
the best way was to use a relay.  Am I correct in saying that?

Basically, 12 volt car battery is used for power source.  Keylock
switch (momentary) in series with a push button switch (momentary).
Just looking for maximum amps.  Can you tell me what size fuse(s) I
should use for this?   Does this fit the bill?  Thank you!

http://i360.photobucket.com/albums/oo49/stockburn/circuit.jpg

The circuit will function. You really don't need two fuses, you can fuse the
pos. output to both the coil and the ignighter.
How many ignighters are you powering at one time?
I can't see a switch not handling one, even a NiCr ignighter.
You can fuse as high as the wire rating or the switch ratings, which ever is
lower.

Tom

OK, great. I will make that change as well,
The # of igniters at this time will only be a max of 5.

When all is said and done, and I have my project box completed. How
in the heck can I measure how many amps are really going through? I
have a multimeter which can measure amps, but how do I put a synthetic
load on the circuit to measure max amps? Maybe just get a small dc
motor with a shaft and make the shaft come to a stall ?

 

[Tom Biasi]

"ULB" <ultralightbackpacker@yahoo.com> wrote in message
news:4820a9bb-18b6-4a4a-b8bd-8c6f67de6dc3@m25g2000yqc.googlegroups.com...
On Jan 4, 12:56 pm, "Tom Biasi" <tombi...@optonline.net> wrote:

"ULB" <ultralightbackpac...@yahoo.com> wrote in message

news:11b18f6d-3eed-4a94-8b47-a6f642f9b3fc@m25g2000yqc.googlegroups.com...

Can someone look this circuit over for me and let me know if it looks
ok, and if any changes are needed?

The design is just a simple control circuit for a rocket launcher.
After posting a few days ago on an amp question (very helpful), it
seems the switches I found can't handle the larger amps, so I figured
the best way was to use a relay. Am I correct in saying that?

Basically, 12 volt car battery is used for power source. Keylock
switch (momentary) in series with a push button switch (momentary).
Just looking for maximum amps. Can you tell me what size fuse(s) I
should use for this? Does this fit the bill? Thank you!

http://i360.photobucket.com/albums/oo49/stockburn/circuit.jpg

The circuit will function. You really don't need two fuses, you can fuse
the
pos. output to both the coil and the ignighter.
How many ignighters are you powering at one time?
I can't see a switch not handling one, even a NiCr ignighter.
You can fuse as high as the wire rating or the switch ratings, which ever
is
lower.

Tom

OK, great. I will make that change as well,
The # of igniters at this time will only be a max of 5.

When all is said and done, and I have my project box completed. How
in the heck can I measure how many amps are really going through? I
have a multimeter which can measure amps, but how do I put a synthetic
load on the circuit to measure max amps? Maybe just get a small dc
motor with a shaft and make the shaft come to a stall ?

Not sure what you mean by a "synthetic" load. If you are looking to see how
many Amps triggered your ignighters you will need a fast reading meter with
a hold capability. Its also important to know for how long the pulse
occurred also.
If you are looking to see how much current your unit can supply it will up
to the fuse or capability of the DC source if less than the fuse.
If the former re-read Jon Kirwan's remarks.

Tom

 

[Jon Kirwan]

On Wed, 6 Jan 2010 15:49:42 -0500, "Tom Biasi"
<tombiasi@optonline.net> wrote:

snip
If you are looking to see how much current your unit can supply it will up
to the fuse or capability of the DC source if less than the fuse.
If the former re-read Jon Kirwan's remarks.

The squib resistance is about 2/3rds of an Ohm. I think they
told me it varied from 0.66 to 0.67 Ohms, with some very very
tight variation. The bridgewire is very short and cut in a
repeatable fashion, I gathered. It's made of AlCr alloy,
though on searching the web I only find an 80/20 alloy and
not many references even to that. So it may include other
things like nickel, for all I know, these days.

If this is for different rockets, there's really no worry,
but one of the problems with firing off squibs in multi-
engine models (and I don't know if the OP intends that), is
getting all 5 _engines_ to fire before the rocket leaves the
pad. This means the timing of the ignition of the pyrogen
itself must occur at the same time -- "same" having the
meaning of __success__ in firing all the engines before the
rocket moves much.

To solve that problem, the energy sufficient to guarantee
ignition needs to be delivered at roughly the same instant. A
heavy car battery and heavy wires is a brute force method to
get there. There are more subtle means. One of the things
I've tried to use is a rocket-pad-local flash-lamp system
using a 4kV trigger voltage from the remote end. The trigger
voltage has almost no current and arrives at the rocket pad
and triggers the flash lamps at the exact same moment -- they
are _very_ repeatable, that way -- dumping the energy from a
cap into each squib.

Jon

 

[David Eather]

Ron M. wrote:

On Jan 6, 4:04 pm, Jon Kirwan <j...@infinitefactors.org> wrote:
On Wed, 6 Jan 2010 15:49:42 -0500, "Tom Biasi"

tombi...@optonline.net> wrote:
snip
If you are looking to see how much current your unit can supply it will up
to the fuse or capability of the DC source if less than the fuse.
If the former re-read Jon Kirwan's remarks.
The squib resistance is about 2/3rds of an Ohm. I think they
told me it varied from 0.66 to 0.67 Ohms, with some very very
tight variation. The bridgewire is very short and cut in a
repeatable fashion, I gathered. It's made of AlCr alloy,
though on searching the web I only find an 80/20 alloy and
not many references even to that. So it may include other
things like nickel, for all I know, these days.

If this is for different rockets, there's really no worry,
but one of the problems with firing off squibs in multi-
engine models (and I don't know if the OP intends that), is
getting all 5 _engines_ to fire before the rocket leaves the
pad. This means the timing of the ignition of the pyrogen
itself must occur at the same time -- "same" having the
meaning of __success__ in firing all the engines before the
rocket moves much.

To solve that problem, the energy sufficient to guarantee
ignition needs to be delivered at roughly the same instant. A
heavy car battery and heavy wires is a brute force method to
get there. There are more subtle means. One of the things
I've tried to use is a rocket-pad-local flash-lamp system
using a 4kV trigger voltage from the remote end. The trigger
voltage has almost no current and arrives at the rocket pad
and triggers the flash lamps at the exact same moment -- they
are _very_ repeatable, that way -- dumping the energy from a
cap into each squib.

Jon

Don't need to go thru all of that. If you just hook them in series

Series? I think you mean parallel

and

provide more than the required all fire current, if the squibs are
consistently made then they all should pop simultaneously. We do this
with e-matches all the time and I don't see any difference except the
required all fire current.

 

[Ron M.]

On Jan 6, 4:04 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

On Wed, 6 Jan 2010 15:49:42 -0500, "Tom Biasi"

tombi...@optonline.net> wrote:
snip
If you are looking to see how much current your unit can supply it will up
to the fuse or capability of the DC source if less than the fuse.
If the former re-read Jon Kirwan's remarks.

The squib resistance is about 2/3rds of an Ohm.  I think they
told me it varied from 0.66 to 0.67 Ohms, with some very very
tight variation.  The bridgewire is very short and cut in a
repeatable fashion, I gathered.  It's made of AlCr alloy,
though on searching the web I only find an 80/20 alloy and
not many references even to that.  So it may include other
things like nickel, for all I know, these days.

If this is for different rockets, there's really no worry,
but one of the problems with firing off squibs in multi-
engine models (and I don't know if the OP intends that), is
getting all 5 _engines_ to fire before the rocket leaves the
pad.  This means the timing of the ignition of the pyrogen
itself must occur at the same time -- "same" having the
meaning of __success__ in firing all the engines before the
rocket moves much.

To solve that problem, the energy sufficient to guarantee
ignition needs to be delivered at roughly the same instant. A
heavy car battery and heavy wires is a brute force method to
get there.  There are more subtle means.  One of the things
I've tried to use is a rocket-pad-local flash-lamp system
using a 4kV trigger voltage from the remote end.  The trigger
voltage has almost no current and arrives at the rocket pad
and triggers the flash lamps at the exact same moment -- they
are _very_ repeatable, that way -- dumping the energy from a
cap into each squib.

Jon

Don't need to go thru all of that. If you just hook them in series and
provide more than the required all fire current, if the squibs are
consistently made then they all should pop simultaneously. We do this
with e-matches all the time and I don't see any difference except the
required all fire current.

 

[Jasen Betts]

On 2010-01-07, David Eather <eather@tpg.com.au> wrote:

Ron M. wrote:
On Jan 6, 4:04 pm, Jon Kirwan <j...@infinitefactors.org> wrote:
On Wed, 6 Jan 2010 15:49:42 -0500, "Tom Biasi"

tombi...@optonline.net> wrote:
snip
If you are looking to see how much current your unit can supply it will up
to the fuse or capability of the DC source if less than the fuse.
If the former re-read Jon Kirwan's remarks.
The squib resistance is about 2/3rds of an Ohm. I think they
told me it varied from 0.66 to 0.67 Ohms, with some very very
tight variation. The bridgewire is very short and cut in a
repeatable fashion, I gathered. It's made of AlCr alloy,
though on searching the web I only find an 80/20 alloy and
not many references even to that. So it may include other
things like nickel, for all I know, these days.

If this is for different rockets, there's really no worry,
but one of the problems with firing off squibs in multi-
engine models (and I don't know if the OP intends that), is
getting all 5 _engines_ to fire before the rocket leaves the
pad. This means the timing of the ignition of the pyrogen
itself must occur at the same time -- "same" having the
meaning of __success__ in firing all the engines before the
rocket moves much.

To solve that problem, the energy sufficient to guarantee
ignition needs to be delivered at roughly the same instant. A
heavy car battery and heavy wires is a brute force method to
get there. There are more subtle means. One of the things
I've tried to use is a rocket-pad-local flash-lamp system
using a 4kV trigger voltage from the remote end. The trigger
voltage has almost no current and arrives at the rocket pad
and triggers the flash lamps at the exact same moment -- they
are _very_ repeatable, that way -- dumping the energy from a
cap into each squib.

Jon

Don't need to go thru all of that. If you just hook them in series

Series? I think you mean parallel

nah series.

if you're worried about one of them self-destructing before the others
have lit up parallel each with a silicon diode or two.

but if you use a pulse that's reasonably fast and not excessively
energetic you should be able to light them all before the first
one goes open-circuit.

putting them in parallel is going to require invonveniently high
currents.

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[ULB]

On Jan 6, 1:04 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

On Wed, 6 Jan 2010 15:49:42 -0500, "Tom Biasi"

tombi...@optonline.net> wrote:
snip
If you are looking to see how much current your unit can supply it will up
to the fuse or capability of the DC source if less than the fuse.
If the former re-read Jon Kirwan's remarks.

The squib resistance is about 2/3rds of an Ohm.  I think they
told me it varied from 0.66 to 0.67 Ohms, with some very very
tight variation.  The bridgewire is very short and cut in a
repeatable fashion, I gathered.  It's made of AlCr alloy,
though on searching the web I only find an 80/20 alloy and
not many references even to that.  So it may include other
things like nickel, for all I know, these days.

If this is for different rockets, there's really no worry,
but one of the problems with firing off squibs in multi-
engine models (and I don't know if the OP intends that), is
getting all 5 _engines_ to fire before the rocket leaves the
pad.  This means the timing of the ignition of the pyrogen
itself must occur at the same time -- "same" having the
meaning of __success__ in firing all the engines before the
rocket moves much.

To solve that problem, the energy sufficient to guarantee
ignition needs to be delivered at roughly the same instant. A
heavy car battery and heavy wires is a brute force method to
get there.  There are more subtle means.  One of the things
I've tried to use is a rocket-pad-local flash-lamp system
using a 4kV trigger voltage from the remote end.  The trigger
voltage has almost no current and arrives at the rocket pad
and triggers the flash lamps at the exact same moment -- they
are _very_ repeatable, that way -- dumping the energy from a
cap into each squib.

Jon

Hi Jon,

Your assumption is correct. I was hoping to build rockets and launch
them with multiple single stage engines all firing at the same time.

If I read your last paragraph correctly, you are suggesting that I
continue to use a 12 volt relay for max amps, but also bolt on a
capacitor also (or many) into the circuit?

Thank you for putting up with me.

 

[Jon Kirwan]

On Thu, 7 Jan 2010 07:44:24 -0800 (PST), ULB
<ultralightbackpacker@yahoo.com> wrote:

On Jan 6, 1:04 pm, Jon Kirwan <j...@infinitefactors.org> wrote:
On Wed, 6 Jan 2010 15:49:42 -0500, "Tom Biasi"

tombi...@optonline.net> wrote:
snip
If you are looking to see how much current your unit can supply it will up
to the fuse or capability of the DC source if less than the fuse.
If the former re-read Jon Kirwan's remarks.

The squib resistance is about 2/3rds of an Ohm.  I think they
told me it varied from 0.66 to 0.67 Ohms, with some very very
tight variation.  The bridgewire is very short and cut in a
repeatable fashion, I gathered.  It's made of AlCr alloy,
though on searching the web I only find an 80/20 alloy and
not many references even to that.  So it may include other
things like nickel, for all I know, these days.

If this is for different rockets, there's really no worry,
but one of the problems with firing off squibs in multi-
engine models (and I don't know if the OP intends that), is
getting all 5 _engines_ to fire before the rocket leaves the
pad.  This means the timing of the ignition of the pyrogen
itself must occur at the same time -- "same" having the
meaning of __success__ in firing all the engines before the
rocket moves much.

To solve that problem, the energy sufficient to guarantee
ignition needs to be delivered at roughly the same instant. A
heavy car battery and heavy wires is a brute force method to
get there.  There are more subtle means.  One of the things
I've tried to use is a rocket-pad-local flash-lamp system
using a 4kV trigger voltage from the remote end.  The trigger
voltage has almost no current and arrives at the rocket pad
and triggers the flash lamps at the exact same moment -- they
are _very_ repeatable, that way -- dumping the energy from a
cap into each squib.

Jon

Hi Jon,

Your assumption is correct. I was hoping to build rockets and launch
them with multiple single stage engines all firing at the same time.

If I read your last paragraph correctly, you are suggesting that I
continue to use a 12 volt relay for max amps, but also bolt on a
capacitor also (or many) into the circuit?

I think your use of a car battery, in this application, is
good. It will have _no_ problems sourcing the current needed
and the squibs will heat quickly. Which is what you want. No
need for a capacitor. In fact, ignore my comments there. It
was just something I experimented with, with an eye to
reducing the need for lugging a huge battery around. (The
capacitors allowed a slow build up of the necessary energy
from much weaker batteries than your car battery.)

While I never actually tried firing _5_ engines at the same
time, I did do _2_ and _3_. I suspect you are probably fine.
If you do have a problem (and you will know it, soon enough),
then we can discuss what you experienced and consider
alternative options. But I suspect you will be fine.
Carefully select your squibs for similarity to each other and
be sure to position them as uniformly as you can inside the
engines. Especially watch out for one or another becoming
loose as you set things up. I suppose you might want to keep
the lead lengths of your cables to each squib of similar
length. But you probably would do that, anyway. Use heavier
gauge wire for longer lengths away from the pad. And use
engines from the same batch and time of manufacture and
storage situations, if possible. Hopefully, there are no
microcracks in the solid fuel, too.

I generally got away from multi-engine firings and just used
larger single engines, instead. More uniformity and
generally less worry and trouble.

Thank you for putting up with me.

Oh, cripes. It's no problem at all. Talk is cheap.

Jon