Help with 12 volt rocket igniter

[ULB]

Hi all,

I was looking into building a simple (but hopefully cool) model rocket
igniter. Yeah I'm bored, but stupid as a brick. About the only thing
I know about electricity is 110 volt hurts when you touch it.
Luckily this is only 12 volts.

You can view the plans here: http://home.earthlink.net/~rbogerjr/index.html

If you scroll down and hit "contents directory" it will show you the
"how it works".

How does the lightbulb limit the current that is going through the
circuit without igniting the engine igniter? I am assuming from what
I have read is anything above 6 volts, ignites it like a fuse blowing.

I would love to build this unit, only I would like to change the
incandescent bulb to an LED in addition, add a piezo for an audible
sound as well. Where should the piezo be added in the diagram?

Can anyone shed some light for me on this? Thank you for any replies
and have a great night.

 

[Tim Wescott]

Hi all,

I was looking into building a simple (but hopefully cool) model rocket
igniter. Yeah I'm bored, but stupid as a brick. About the only thing
I know about electricity is 110 volt hurts when you touch it.
Luckily this is only 12 volts.

You can view the plans here: http://home.earthlink.net/~rbogerjr/index.html

If you scroll down and hit "contents directory" it will show you the
"how it works".

How does the lightbulb limit the current that is going through the
circuit without igniting the engine igniter? I am assuming from what
I have read is anything above 6 volts, ignites it like a fuse blowing.

For this to work, the light bulb has to have a much higher resistance
than the igniter so that it limits the current. When you arm the box
with the key switch the power is applied through the bulb to the
igniter. The bulb, having a much higher resistance than the igniter,
takes all the voltage, and lights up leaving very little current for the
igniter. When you close the ignition switch you short out the bulb, the
full 6V gets applied to the igniter, and the rocket (we hope) goes off.

I would love to build this unit, only I would like to change the
incandescent bulb to an LED in addition, add a piezo for an audible
sound as well. Where should the piezo be added in the diagram?

Can anyone shed some light for me on this? Thank you for any replies
and have a great night.

Safety disclaimer: Rockets can kill an/or injure, I'm not getting paid,
safety is your responsibility, if you're under 18 I didn't write this,
you hurt yourself it's your dime, yadda yadda.

If you can get a piezo that will work on 6V you can hook it up in
parallel with the lamp or LED. As long as it doesn't take too much
current it'll sound without igniting the rocket. You can hook up the
LED where the lamp was with an appropriate series resistor in series
with the LED.

You should be able to put this together so that an LED and a piezo
together will consume less current than just the lamp, and that's what
you should aim for. I very much doubt that you can get detailed
specifications on just what makes your igniter fire off, so you're
reduced to either blindly copying what's already been done, or trying to
pry safety information out of a manufacturer (they'll tell you: "just
use our box, we don't release that information, yadda yadda". They'll
do this because their product liability insurance requires them to).

Whatever else you do, do some research into exactly what makes these
igniters fire, and do some measurements to make sure that your box won't
make them fire unexpectedly. Whatever box I built, for each one I'd
check it with an ammeter first, to verify that the current was too low
to fire an igniter until all appropriate buttons/keys/wingwazzles were
appropriately activated. In fact, if I were good I'd do this each time
I was getting ready to set out to fire off some rockets.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[ehsjr]

Hi all,

I was looking into building a simple (but hopefully cool) model rocket
igniter. Yeah I'm bored, but stupid as a brick. About the only thing
I know about electricity is 110 volt hurts when you touch it.
Luckily this is only 12 volts.

You can view the plans here: http://home.earthlink.net/~rbogerjr/index.html

If you scroll down and hit "contents directory" it will show you the
"how it works".

How does the lightbulb limit the current that is going through the
circuit without igniting the engine igniter? I am assuming from what
I have read is anything above 6 volts, ignites it like a fuse blowing.

I would love to build this unit, only I would like to change the
incandescent bulb to an LED in addition, add a piezo for an audible
sound as well. Where should the piezo be added in the diagram?

Can anyone shed some light for me on this? Thank you for any replies
and have a great night.

If the referenced plans are correct, then the lamp they
use draws 150 mA when lit, and around 500 mA when cold.
It would be wise to reduce that current.

When you use the LED as you plan to do, it will draw
*way* less, and that is safer. Modifying the diagram
at the site to include the led and piezo:

/
+---[igniter]---o o---+---[330R]---[LED]---+
| SW1 | |
| | |
| +------[Piezo]-------+
[Batt] 6V | |
| | / |
| +--------o o--------+
| SW2 |
| |
+-------------------------------------------+

Use a piezo that draws 10 mA or less, such as CAT# SBZ-365
from AllElectronics, and the total draw for the LED and
piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.

See and follow all the safety points Tim mentioned.

Ed

 

[ULB]

Hi all,

I was looking into building a simple (but hopefully cool) model rocket
igniter. Yeah I'm bored, but stupid as a brick. About the only thing
I know about electricity is 110 volt hurts when you touch it.
Luckily this is only 12 volts.

You can view the plans here: http://home.earthlink.net/~rbogerjr/index.html

If you scroll down and hit "contents directory" it will show you the
"how it works".

How does the lightbulb limit the current that is going through the
circuit without igniting the engine igniter? I am assuming from what
I have read is anything above 6 volts, ignites it like a fuse blowing.

I would love to build this unit, only I would like to change the
incandescent bulb to an LED in addition, add a piezo for an audible
sound as well. Where should the piezo be added in the diagram?

Can anyone shed some light for me on this? Thank you for any replies
and have a great night.

Tim and ehsjr,

Thank you for responding. I really am having a hard time grasping the
resistor. I understand it reduces voltage etc, but I do not
understand if it is like a hose, whereas the ouput is less, and
anything prior to that resistor is the original voltage.

I just drew up a plan based on the above rocket launcher. I was at
work today and read the internet instead of working. Don't tell my
boss. You can tell I didn't comprehend much.

In any case, I have changed the design slightly, well probably alot.
The launcher is now to be keyed, when turned in the 'on' position, it
shows the voltage in the battery(s), lights an LED and buzzes a
piezo. There is no longer a connectivity test to the igntiter
(probably safer I would hazard a guess). The launch button lights an
LED and then shorts the igniter and hopefully the rocket launches.
How do I keep the "launch" button LED Lit even if it doesn't fire? I
think I am missing a wire.

Thanks for the patience. Here is the link to my umm err drawing.

http://img247.imageshack.us/img247/7237/hpim0846cw4.jpg

 

[ULB]

Tim and ehsjr,

Thank you for responding. I really am having a hard time grasping the
resistor. I understand it reduces voltage etc, but I do not
understand if it is like a hose, whereas the ouput is less, and
anything prior to that resistor is the original voltage.

I just drew up a plan based on the above rocket launcher. I was at
work today and read the internet instead of working. Don't tell my
boss. You can tell I didn't comprehend much.

In any case, I have changed the design slightly, well probably alot.
The launcher is now to be keyed, when turned in the 'on' position, it
shows the voltage in the battery(s), lights an LED and buzzes a
piezo. There is no longer a connectivity test to the igntiter
(probably safer I would hazard a guess). The launch button lights an
LED and then shorts the igniter and hopefully the rocket launches.
How do I keep the "launch" button LED Lit even if it doesn't fire? I
think I am missing a wire.

Thanks for the patience. Here is the link to my umm err drawing.

http://img247.imageshack.us/img247/7237/hpim0846cw4.jpg

Somehow the image is not working. Please try this one.

http://img160.imageshack.us/my.php?image=hpim0846be0.jpg

 

[default]

Thank you for responding. I really am having a hard time grasping the
resistor. I understand it reduces voltage etc, but I do not
understand if it is like a hose, whereas the ouput is less, and
anything prior to that resistor is the original voltage.

You got it.

Potential (pressure) is in the main hose, the resistor is like a
capillary tube and only allows a small bit of current (water) to flow
and go back to the source (other terminal of the battery).

Same concepts as water flow. A high pressure can send a stream
further, a high current means a lot of water is moving.

The battery is the source of pressure. When the led is in series with
the igniter it is like a tiny capillary and relatively little power is
allowed to go to the load (igniter). Close the "fire" switch and the
full battery power goes (more current is allowed to flow) to the
igniter and it gets very hot and ignites the fuel.

There are still risks involved even if you minimize the current in the
wires while checking the "armed" state with the tiny current.
Transmitters and even lightening flashes can induce (couple
magnetically) enough voltage into your squib/igniter to cause it to
fire unexpectedly. The reason you see signs "Blasting - turn off all
two way radios."

Your propellant is less active than some explosives, but do be
careful. The battery should be the last thing you connect and then
well away from the rocket. In my youth we used fuses and spark coils
to ignite our rockets and cannons. If the rocket doesn't fire
disconnect the battery and wait before investigating. An ammeter in
series with the squib will tell you that current is going to heat the
squib and you should see it go to zero when the squib burns out.

Your drawing leaves a lot to be desired. It looks as if you have a
wire (pencil line) around both the armed indicator and squib - if
that's the case neither will work since the wire has a lower
resistance than either the armed indicator or igniter and electricity
will flow via those routes in preference to the way you want it to go.

The ASCII schematic someone already sent it the way to draw and wire
it and much more clear than block drawings.

Another good hobby of my youth was hydrogen filled balloons - all it
takes is lye (caustic soda) and aluminum foil, some plumbing to
contain the reaction, cool and direct the gas to a balloon. At night
we sent up flares with long fuses and the balloons would be over a
mile away before the flare ignited and eventually balloon. Big yellow
flare in the sky and satisfying thump a few seconds later. We had a
wide river and would watch the wind direction so there was little
problem if the flare detached before it was expended. It is dangerous
but more so to the people and objects downwind. disclaimer: Don't do
it.
--

 

[Sambo]

Somehow the image is not working. Please try this one.

http://img160.imageshack.us/my.php?image=hpim0846be0.jpg

I am not sure about the second link , because is asked to sign in and
showed no image. The first will fire a rocket but the ignition led
will never light because it is bypassed by (near) 0 resistance.
You should hook up the launch button across the LED and it's resistor.
Now when you try to launch and nothing happens, the led will tell you
( after releasing the button ) if the fuse is still good or not ( it is
possible for the fuse to go off and the fuel not to ignite ) .

Cheers


(WOOOHOO another vicarious experience)

 

[Sambo]

Oh one other tip about taking closeup pictures, tape piece of thin mate
paper ever / in front of the flash. Loosely hanging out and over toilet
paper works for me.

 

[Ecnerwal]

/
+---[igniter]---o o---+---[330R]---[LED]---+
| SW1 | |
| | |
| +------[Piezo]-------+
[Batt] 6V | |
| | / |
| +--------o o--------+
| SW2 |
| |
+-------------------------------------------+

Use a piezo that draws 10 mA or less, such as CAT# SBZ-365
from AllElectronics, and the total draw for the LED and
piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.

A slightly different, perhaps better, version:
/
+------o o--+-----+---+---[580R]---[LED-G]-+----------+
| SW1 | | | | |
| | | | / | |
| [580R] | +--------o o--------+ |
[Batt] 6V | | SW2 |
| or | [Piezo] [ignitor]
| 12V | | |
| [LED-R] | |
| | | |
+------------+-----+-----------------------------------+

SW1 should be a keyed switch which can only have the key removed when
off. The key should always be in hand when approaching the rocket.

The LEDs will light, albeit not very brightly, with 6V. In my
experience, 12V is more reliable for launching, and easier to find. If
doing a dedicated 6V version, go back to the 330 or 280 ohms.

In this version, LED-R (red) and the annoying noise both indicate that
the arming switch (SW1) is on, and that there is power. If the annoying
noise is on, don't approach rocket - that's an improvement (IMHO) over
Ed's version in terms of safety, if using a noisemaker. The current from
those does not pass through the ignitor.

LED-G (green) indicates a good connection of the ignitor wires (though
it can't tell a short from an ignitor, so be careful when connecting
wires at the rocket.) SW2 is the launch pushbutton.

Regardless of what circuit you use, remember not to approach the rocket
for at least a minute in the event of a launch failure. Sometimes they
smolder and go off.

If you like, you can replicate the right side of the circuit (beyond the
piezo) to make a multiple-rocket launcher (where you'd set up 2 or more
launch rods and rockets, and launch either at the same time, or in quick
succession). In practice I've found that this is not usually very
useful, as it increases the likelihood of losing the rockets, trying to
track more than one at a time.

 

[ULB]

/
+---[igniter]---o o---+---[330R]---[LED]---+
| SW1 | |
| | |
| +------[Piezo]-------+
[Batt] 6V | |
| | / |
| +--------o o--------+
| SW2 |
| |
+-------------------------------------------+

Use a piezo that draws 10 mA or less, such as CAT# SBZ-365
from AllElectronics, and the total draw for the LED and
piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.

A slightly different, perhaps better, version:
/
+------o o--+-----+---+---[580R]---[LED-G]-+----------+
| SW1 | | | | |
| | | | / | |
| [580R] | +--------o o--------+ |
[Batt] 6V | | SW2 |
| or | [Piezo] [ignitor]
| 12V | | |
| [LED-R] | |
| | | |
+------------+-----+-----------------------------------+

SW1 should be a keyed switch which can only have the key removed when
off. The key should always be in hand when approaching the rocket.

The LEDs will light, albeit not very brightly, with 6V. In my
experience, 12V is more reliable for launching, and easier to find. If
doing a dedicated 6V version, go back to the 330 or 280 ohms.

In this version, LED-R (red) and the annoying noise both indicate that
the arming switch (SW1) is on, and that there is power. If the annoying
noise is on, don't approach rocket - that's an improvement (IMHO) over
Ed's version in terms of safety, if using a noisemaker. The current from
those does not pass through the ignitor.

LED-G (green) indicates a good connection of the ignitor wires (though
it can't tell a short from an ignitor, so be careful when connecting
wires at the rocket.) SW2 is the launch pushbutton.

Regardless of what circuit you use, remember not to approach the rocket
for at least a minute in the event of a launch failure. Sometimes they
smolder and go off.

If you like, you can replicate the right side of the circuit (beyond the
piezo) to make a multiple-rocket launcher (where you'd set up 2 or more
launch rods and rockets, and launch either at the same time, or in quick
succession). In practice I've found that this is not usually very
useful, as it increases the likelihood of losing the rockets, trying to
track more than one at a time.

Thank you all very much.

I went down to the local radio shack and got a bread board. Wired it
all up. Everything seems fine. I do have two questions.

When I push the launch button all LED die off If an igniter is in
place). I even tried using 12 volt incandescent lights minus the
resistors and same problem. I am assuming this is because of the
"short"? Is the above by design? Perhaps I mis wired it but I do not
believe so. I played for 12 hours today. LOL.

Second question: While trying to mimic the Igniter (I went through 8
of them), I just used a jumper cable, same issue, all lights go off.
However, if I leave the jumper on, boy does the battery (12 AA 1.5
volt) get hot. To the point I can tell something is definately
amiss. I went back to Radio shack and got some diodes. Didn't fix
the issue. I "Worry" about this as the final solution would be to use
my car battery, and I certainly don't want to fry anything in the
vehicle

Thank you all for any responses and helping a newb.

 

[ehsjr]

/
+---[igniter]---o o---+---[330R]---[LED]---+
| SW1 | |
| | |
| +------[Piezo]-------+
[Batt] 6V | |
| | / |
| +--------o o--------+
| SW2 |
| |
+-------------------------------------------+

Use a piezo that draws 10 mA or less, such as CAT# SBZ-365
from AllElectronics, and the total draw for the LED and
piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.

A slightly different, perhaps better, version:
/
+------o o--+-----+---+---[580R]---[LED-G]-+----------+
| SW1 | | | | |
| | | | / | |
| [580R] | +--------o o--------+ |
[Batt] 6V | | SW2 |
| or | [Piezo] [ignitor]
| 12V | | |
| [LED-R] | |
| | | |
+------------+-----+-----------------------------------+

SW1 should be a keyed switch which can only have the key removed when
off. The key should always be in hand when approaching the rocket.

The LEDs will light, albeit not very brightly, with 6V. In my
experience, 12V is more reliable for launching, and easier to find. If
doing a dedicated 6V version, go back to the 330 or 280 ohms.

In this version, LED-R (red) and the annoying noise both indicate that
the arming switch (SW1) is on, and that there is power. If the annoying
noise is on, don't approach rocket - that's an improvement (IMHO) over
Ed's version in terms of safety, if using a noisemaker. The current from
those does not pass through the ignitor.

LED-G (green) indicates a good connection of the ignitor wires (though
it can't tell a short from an ignitor, so be careful when connecting
wires at the rocket.) SW2 is the launch pushbutton.

Regardless of what circuit you use, remember not to approach the rocket
for at least a minute in the event of a launch failure. Sometimes they
smolder and go off.

If you like, you can replicate the right side of the circuit (beyond the
piezo) to make a multiple-rocket launcher (where you'd set up 2 or more
launch rods and rockets, and launch either at the same time, or in quick
succession). In practice I've found that this is not usually very
useful, as it increases the likelihood of losing the rockets, trying to
track more than one at a time.

Thank you all very much.

I went down to the local radio shack and got a bread board. Wired it
all up. Everything seems fine. I do have two questions.

When I push the launch button all LED die off If an igniter is in
place). I even tried using 12 volt incandescent lights minus the
resistors and same problem. I am assuming this is because of the
"short"? Is the above by design? Perhaps I mis wired it but I do not
believe so. I played for 12 hours today. LOL.

Yes, the circuit I provided is designed to turn off the LED
when the launch button (sw2) is pressed.

Use a 12 volt tail light bulb in place of the igniter for
your tests. See below for what the indicators should do.

Second question: While trying to mimic the Igniter (I went through 8
of them), I just used a jumper cable, same issue, all lights go off.
However, if I leave the jumper on, boy does the battery (12 AA 1.5
volt) get hot. To the point I can tell something is definately
amiss. I went back to Radio shack and got some diodes. Didn't fix
the issue. I "Worry" about this as the final solution would be to use
my car battery, and I certainly don't want to fry anything in the
vehicle

With the 12 volt bulb installed in place of the igniter,
you should be able to see (literally) if there is a wiring
error. The 12 volt bulb must not glow until both switch
1 and switch 2 are on.

You mentioned 12 AA batteries - that gives you a total
of 18 volts. Use 8 AA batteries to get 12 volts.

With a jumper installed in place of the igniter (not
a good thing to do), the only way that batteries can
get hot is if SW2 is in the on position. That assumes
the system is "armed" by switch 1 in the on position.
But aside from that, the jumper will short your batteries
when switch 2 is on (again, if the circuit is "armed" by
switch 1 being on). Don't use the jumper! You don't
want to short your batteries, and you don't want them
to get hot.

When you install a 12 volt bulb in place of the igniter,
and use 12 volts to power the circuit, the indications
should be as follows: (view in fixed font)

Condition INDICATORS
SW1 SW2 LED PIEZO BULB
========= ===============
off off off off off
ON off ON ON off
ON ON off off ON

Ed

 

[ULB]

On Mar 4, 10:50 am, Ecnerwal <[email protected]>
wrote:

                   /
   +---[igniter]---o  o---+---[330R]---[LED]---+
   |               SW1    |                    |
   |                      |                    |
   |                      +------[Piezo]-------+
 [Batt] 6V                |                    |
   |                      |         /          |
   |                      +--------o  o--------+
   |                                SW2        |
   |                                           |
   +-------------------------------------------+
Use a piezo that draws 10 mA or less, such as CAT# SBZ-365
from AllElectronics, and the total draw for the LED and
piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.
A slightly different, perhaps better, version:
            /
    +------o  o--+-----+---+---[580R]---[LED-G]-+----------+
    |       SW1  |     |   |                    |          |
    |            |     |   |         /          |          |
    |          [580R]  |   +--------o  o--------+          |
  [Batt] 6V      |     |             SW2                   |
    |     or     |  [Piezo]                           [ignitor]
    |    12V     |     |                                   |
    |         [LED-R]  |                                   |
    |            |     |                                   |
    +------------+-----+-----------------------------------+
SW1 should be a keyed switch which can only have the key removed when
off. The key should always be in hand when approaching the rocket.
The LEDs will light, albeit not very brightly, with 6V. In my
experience, 12V is more reliable for launching, and easier to find. If
doing a dedicated 6V version, go back to the 330 or 280 ohms.
In this version, LED-R (red) and the annoying noise both indicate that
the arming switch (SW1) is on, and that there is power. If the annoying
noise is on, don't approach rocket - that's an improvement (IMHO) over
Ed's version in terms of safety, if using a noisemaker. The current from
those does not pass through the ignitor.
LED-G (green) indicates a good connection of the ignitor wires (though
it can't tell a short from an ignitor, so be careful when connecting
wires at the rocket.) SW2 is the launch pushbutton.
Regardless of what circuit you use, remember not to approach the rocket
for at least a minute in the event of a launch failure. Sometimes they
smolder and go off.
If you like, you can replicate the right side of the circuit (beyond the
piezo) to make a multiple-rocket launcher (where you'd set up 2 or more
launch rods and rockets, and launch either at the same time, or in quick
succession). In practice I've found that this is not usually very
useful, as it increases the likelihood of losing the rockets, trying to
track more than one at a time.

Thank you all very much.

I went down to the local radio shack and got a bread board.  Wired it
all up.  Everything seems fine.  I do have two questions.

When I push the launch button all LED die off If an igniter is in
place).  I even tried using 12 volt incandescent lights minus the
resistors and same problem.  I am assuming this is because of the
"short"?  Is the above by design?  Perhaps I mis wired it but I do not
believe so.  I played for 12 hours today.  LOL.

Yes, the circuit I provided is designed to turn off the LED
when the launch button (sw2) is pressed.

Use a 12 volt tail light bulb in place of the igniter for
your tests. See below for what the indicators should do.

Second question:  While trying to mimic the Igniter (I went through 8
of them), I just used a jumper cable, same issue, all lights go off.
However, if I leave the jumper on, boy does the battery (12 AA 1.5
volt) get hot.  To the point I can tell something is definately
amiss.  I went back to Radio shack and got some diodes.  Didn't fix
the issue.  I "Worry" about this as the final solution would be to use
my car battery, and I certainly don't want to fry anything in the
vehicle

With the 12 volt bulb installed in place of the igniter,
you should be able to see (literally) if there is a wiring
error. The 12 volt bulb must not glow until both switch
1 and switch 2 are on.

You mentioned 12 AA batteries - that gives you a total
of 18 volts.  Use 8 AA batteries to get 12 volts.

With a jumper installed in place of the igniter (not
a good thing to do), the only way that batteries can
get hot is if SW2 is in the on position. That assumes
the system is "armed" by switch 1 in the on position.
But aside from that, the jumper will short your batteries
when switch 2 is on (again, if the circuit is "armed" by
switch 1 being on).  Don't use the jumper! You don't
want to short your batteries, and you don't want them
to get hot.

When you install a 12 volt bulb in place of the igniter,
and use 12 volts to power the circuit, the indications
should be as follows: (view in fixed font)

  Condition            INDICATORS
  SW1   SW2            LED PIEZO  BULB
  =========            ===============
  off   off            off  off   off
  ON    off            ON   ON    off
  ON    ON             off  off   ON

Ed

Thank you all for any responses and helping a newb.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks Ed.

I will head to to Radio shack and get another lamp with assembly. It
appears I am wired up good now.

BTW, if I wanted the LED to stay on while I hit the launch button, how
would I go about changing the circuit? Or is this not best practice?

Thanks again.

 

[Ecnerwal]

When I push the launch button all LED die off If an igniter is in
place). I even tried using 12 volt incandescent lights minus the
resistors and same problem. I am assuming this is because of the
"short"? Is the above by design? Perhaps I mis wired it but I do not
believe so. I played for 12 hours today. LOL.

Second question: While trying to mimic the Igniter (I went through 8
of them), I just used a jumper cable, same issue, all lights go off.
However, if I leave the jumper on, boy does the battery (12 AA 1.5
volt) get hot. To the point I can tell something is definately
amiss. I went back to Radio shack and got some diodes. Didn't fix
the issue. I "Worry" about this as the final solution would be to use
my car battery, and I certainly don't want to fry anything in the
vehicle

As Ed said, 12 1.5V batteries are 18V, not 12. Cut back to 8 (or 10 if
nicad/nimh rechargeables at about 1.2V each).

It is normal for the the LEDs to drop out. In my version, LED-G will
definitely drop out (SW2 shorts it) and LED-R and the piezo may or may
not drop out (but will definitely dim) depending on the battery source
impedance (internal resistance of the battery + resistance of the wires
leading from the battery) and resistance of the wires running to the
launch pad, as well as the ignitor resistance. When testing with no long
wire (which adds some resistance) to the launch pad and AAs
(particularly non-rechargeable ones, which have a relatively high source
impedance) as the battery, I'd expect those to both drop out as well.

A light bulb is a better test item than a dead short/jumper.

With a car battery as the source and long wires out the launch pad, I'd
expect LED-R and the piezo to stay on in my version - but it's not a big
deal if they don't. The main thing to check for correct/safe operation
is that nothing happens with the test bulb if SW1 is not on (pressing
SW2 should have no effect), and nothing happens with the test bulb if
SW2 is not pressed (SW1 on or off), and that the test bulb lights if SW1
is on and SW2 is pressed.

Use a lighter plug to connect to the car - that will put a heavy fuse in
line with the battery supply, which I neglected to draw.

In any case, SW2 should not be held on for more than a few (1-5)
seconds. If the ignitor has not gone by 5 seconds, something is wrong.

 

[ehsjr]

On Mar 4, 10:50 am, Ecnerwal <[email protected]>
wrote:

ehsjr <[email protected]> wrote:

/
+---[igniter]---o o---+---[330R]---[LED]---+
| SW1 | |
| | |
| +------[Piezo]-------+
[Batt] 6V | |
| | / |
| +--------o o--------+
| SW2 |
| |
+-------------------------------------------+

Use a piezo that draws 10 mA or less, such as CAT# SBZ-365

from AllElectronics, and the total draw for the LED and

piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.

A slightly different, perhaps better, version:
/
+------o o--+-----+---+---[580R]---[LED-G]-+----------+
| SW1 | | | | |
| | | | / | |
| [580R] | +--------o o--------+ |
[Batt] 6V | | SW2 |
| or | [Piezo] [ignitor]
| 12V | | |
| [LED-R] | |
| | | |
+------------+-----+-----------------------------------+

SW1 should be a keyed switch which can only have the key removed when
off. The key should always be in hand when approaching the rocket.

The LEDs will light, albeit not very brightly, with 6V. In my
experience, 12V is more reliable for launching, and easier to find. If
doing a dedicated 6V version, go back to the 330 or 280 ohms.

In this version, LED-R (red) and the annoying noise both indicate that
the arming switch (SW1) is on, and that there is power. If the annoying
noise is on, don't approach rocket - that's an improvement (IMHO) over
Ed's version in terms of safety, if using a noisemaker. The current from
those does not pass through the ignitor.

LED-G (green) indicates a good connection of the ignitor wires (though
it can't tell a short from an ignitor, so be careful when connecting
wires at the rocket.) SW2 is the launch pushbutton.

Regardless of what circuit you use, remember not to approach the rocket
for at least a minute in the event of a launch failure. Sometimes they
smolder and go off.

If you like, you can replicate the right side of the circuit (beyond the
piezo) to make a multiple-rocket launcher (where you'd set up 2 or more
launch rods and rockets, and launch either at the same time, or in quick
succession). In practice I've found that this is not usually very
useful, as it increases the likelihood of losing the rockets, trying to
track more than one at a time.

Thank you all very much.

I went down to the local radio shack and got a bread board. Wired it
all up. Everything seems fine. I do have two questions.

When I push the launch button all LED die off If an igniter is in
place). I even tried using 12 volt incandescent lights minus the
resistors and same problem. I am assuming this is because of the
"short"? Is the above by design? Perhaps I mis wired it but I do not
believe so. I played for 12 hours today. LOL.

Yes, the circuit I provided is designed to turn off the LED
when the launch button (sw2) is pressed.

Use a 12 volt tail light bulb in place of the igniter for
your tests. See below for what the indicators should do.

Second question: While trying to mimic the Igniter (I went through 8
of them), I just used a jumper cable, same issue, all lights go off.
However, if I leave the jumper on, boy does the battery (12 AA 1.5
volt) get hot. To the point I can tell something is definately
amiss. I went back to Radio shack and got some diodes. Didn't fix
the issue. I "Worry" about this as the final solution would be to use
my car battery, and I certainly don't want to fry anything in the
vehicle

With the 12 volt bulb installed in place of the igniter,
you should be able to see (literally) if there is a wiring
error. The 12 volt bulb must not glow until both switch
1 and switch 2 are on.

You mentioned 12 AA batteries - that gives you a total
of 18 volts. Use 8 AA batteries to get 12 volts.

With a jumper installed in place of the igniter (not
a good thing to do), the only way that batteries can
get hot is if SW2 is in the on position. That assumes
the system is "armed" by switch 1 in the on position.
But aside from that, the jumper will short your batteries
when switch 2 is on (again, if the circuit is "armed" by
switch 1 being on). Don't use the jumper! You don't
want to short your batteries, and you don't want them
to get hot.

When you install a 12 volt bulb in place of the igniter,
and use 12 volts to power the circuit, the indications
should be as follows: (view in fixed font)

Condition INDICATORS
SW1 SW2 LED PIEZO BULB
========= ===============
off off off off off
ON off ON ON off
ON ON off off ON

Ed

Thank you all for any responses and helping a newb.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Thanks Ed.

I will head to to Radio shack and get another lamp with assembly. It
appears I am wired up good now.

BTW, if I wanted the LED to stay on while I hit the launch button, how
would I go about changing the circuit? Or is this not best practice?

I'm not sure where/how "best practice" fits in or what
you have in mind by the phrase. The fact that the LED
turned off gives you more information than if it remains
on - it tells you that sw2 worked properly, and that a
launch was attempted. If the LED stayed on when the launch
button (sw2) was pressed in the circuit I posted, it would
tell you that sw2 was not working, or that you did not press
it hard enough. If it goes out when you press the button
and comes back on when you release it, it tells you that
the igniter in the rocket did not work.

So the question is, what do you have in mind when you want
the LED to stay on - why do you want that?

Ed

 

[ULB]

ULB wrote:
On Mar 4, 10:50 am, Ecnerwal <[email protected]>
wrote:

                  /
  +---[igniter]---o  o---+---[330R]---[LED]---+
  |               SW1    |                    |
  |                      |                    |
  |                      +------[Piezo]-------+
[Batt] 6V                |                    |
  |                      |         /         |
  |                      +--------o  o--------+
  |                                SW2        |
  |                                           |
  +-------------------------------------------+
Use a piezo that draws 10 mA or less, such as CAT# SBZ-365
from AllElectronics, and the total draw for the LED and
piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.
A slightly different, perhaps better, version:
           /
   +------o  o--+-----+---+---[580R]---[LED-G]-+----------+
   |       SW1  |     |   |                   |          |
   |            |     |   |         /          |          |
   |          [580R]  |   +--------o  o--------+          |
 [Batt] 6V      |     |             SW2                   |
   |     or     |  [Piezo]                           [ignitor]
   |    12V     |     |                                   |
   |         [LED-R]  |                                  |
   |            |     |                                   |
   +------------+-----+-----------------------------------+
SW1 should be a keyed switch which can only have the key removed when
off. The key should always be in hand when approaching the rocket.
The LEDs will light, albeit not very brightly, with 6V. In my
experience, 12V is more reliable for launching, and easier to find. If
doing a dedicated 6V version, go back to the 330 or 280 ohms.
In this version, LED-R (red) and the annoying noise both indicate that
the arming switch (SW1) is on, and that there is power. If the annoying
noise is on, don't approach rocket - that's an improvement (IMHO) over
Ed's version in terms of safety, if using a noisemaker. The current from
those does not pass through the ignitor.
LED-G (green) indicates a good connection of the ignitor wires (though
it can't tell a short from an ignitor, so be careful when connecting
wires at the rocket.) SW2 is the launch pushbutton.
Regardless of what circuit you use, remember not to approach the rocket
for at least a minute in the event of a launch failure. Sometimes they
smolder and go off.
If you like, you can replicate the right side of the circuit (beyond the
piezo) to make a multiple-rocket launcher (where you'd set up 2 or more
launch rods and rockets, and launch either at the same time, or in quick
succession). In practice I've found that this is not usually very
useful, as it increases the likelihood of losing the rockets, trying to
track more than one at a time.
--
Cats, coffee, chocolate...vices to live by
Thank you all very much.
I went down to the local radio shack and got a bread board.  Wired it
all up.  Everything seems fine.  I do have two questions.
When I push the launch button all LED die off If an igniter is in
place).  I even tried using 12 volt incandescent lights minus the
resistors and same problem.  I am assuming this is because of the
"short"?  Is the above by design?  Perhaps I mis wired it but I do not
believe so.  I played for 12 hours today.  LOL.
Yes, the circuit I provided is designed to turn off the LED
when the launch button (sw2) is pressed.
Use a 12 volt tail light bulb in place of the igniter for
your tests. See below for what the indicators should do.
Second question:  While trying to mimic the Igniter (I went through 8
of them), I just used a jumper cable, same issue, all lights go off.
However, if I leave the jumper on, boy does the battery (12 AA 1.5
volt) get hot.  To the point I can tell something is definately
amiss.  I went back to Radio shack and got some diodes.  Didn't fix
the issue.  I "Worry" about this as the final solution would be to use
my car battery, and I certainly don't want to fry anything in the
vehicle
With the 12 volt bulb installed in place of the igniter,
you should be able to see (literally) if there is a wiring
error. The 12 volt bulb must not glow until both switch
1 and switch 2 are on.
You mentioned 12 AA batteries - that gives you a total
of 18 volts.  Use 8 AA batteries to get 12 volts.
With a jumper installed in place of the igniter (not
a good thing to do), the only way that batteries can
get hot is if SW2 is in the on position. That assumes
the system is "armed" by switch 1 in the on position.
But aside from that, the jumper will short your batteries
when switch 2 is on (again, if the circuit is "armed" by
switch 1 being on).  Don't use the jumper! You don't
want to short your batteries, and you don't want them
to get hot.
When you install a 12 volt bulb in place of the igniter,
and use 12 volts to power the circuit, the indications
should be as follows: (view in fixed font)
 Condition            INDICATORS
 SW1   SW2            LED PIEZO  BULB
 =========            ===============
 off   off            off  off   off
 ON    off            ON   ON    off
 ON    ON             off  off   ON
Ed
Thank you all for any responses and helping a newb.- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -

Thanks Ed.

I will head to to Radio shack and get another lamp with assembly.  It
appears I am wired up good now.

BTW, if I wanted the LED to stay on while I hit the launch button, how
would I go about changing the circuit?  Or is this not best practice?

I'm not sure where/how "best practice" fits in or what
you have in mind by the phrase.  The fact that the LED
turned off gives you more information than if it remains
on - it tells you that sw2 worked properly, and that a
launch was attempted.  If the LED stayed on when the launch
button (sw2) was pressed in the circuit I posted, it would
tell you that sw2 was not working, or that you did not press
it hard enough. If it goes out when you press the button
and comes back on when you release it, it tells you that
the igniter in the rocket did not work.

So the question is, what do you have in mind when you want
the LED to stay on - why do you want that?

Ed

Thanks again.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

I see your point. I will keep the design as is.

BTW, I had a typo on one of my previous emails, where I had stated I
had 12 AA's, I have 8 AA's with a total of about 12 volts depending on
bettery condition.

Thanks all. I certainly learned alot, and probably more confused than
before, but playing around with this stuff is really cool.

Here is another question. I have a 16 volt laptop AC to DC Adapter.
The laptop is broke, so I cut the ends off and was going to attempt to
use the AC/DC adapter as my 12 volt source so I don't keep running our
of batteries when playing around. I put in a resistor rated at 560
ohm, and it didn't drop the current at all. Why does a resistor when
placed in front of an LED drop the voltage but not on the AC/DC
adapter? Or perhaps I need a larger resistor? I even put 3 x 560 ohm
resistors in series and didn't nothing to the voltage.

Take care, and thanks.

 

[ehsjr]

ULB wrote:

I see your point. I will keep the design as is.

BTW, I had a typo on one of my previous emails, where I had stated I
had 12 AA's, I have 8 AA's with a total of about 12 volts depending on
bettery condition.

Thanks all. I certainly learned alot, and probably more confused than
before, but playing around with this stuff is really cool.

Here is another question. I have a 16 volt laptop AC to DC Adapter.
The laptop is broke, so I cut the ends off and was going to attempt to
use the AC/DC adapter as my 12 volt source so I don't keep running our
of batteries when playing around. I put in a resistor rated at 560
ohm, and it didn't drop the current at all. Why does a resistor when
placed in front of an LED drop the voltage but not on the AC/DC
adapter? Or perhaps I need a larger resistor? I even put 3 x 560 ohm
resistors in series and didn't nothing to the voltage.

Take care, and thanks.

Sounds like you are measuring the adapter voltage
with a resistor (or resistors) in series with your
meter leads. You will get very little voltage
drop that way, because the meter draws an extremely
small amount of current - roughly 1.6 microamps
assuming a 10 megohm meter and a 16 volt adapter.
The voltage drop is equal to the current times the
resistance, so your 3 560 ohm resistors (1680 ohms total)
would drop .002688 (1680 * .0000016) volts.

But, if you installed the 1680 ohms in series with an
LED and connected the adapter, the LED would draw
roughly 8.5 mA through the 1680 ohms, and the voltage
drop across the resistance would be 14.28 (1680 * .0085)

Ok all that said, you won't be able to use the adapter
with a 560 ohm resistor in series to provide _12_ volt
power for the igniter. However, if the igniter will
work at _16_ volts, you can use the circuit posted.
Just replace the single resistor in the posted circuit
with the three 560 ohm resistors you have, wired in
series for 1680 ohms total. The resistor in the
circuit posted lowers the voltage to the LED, but does
not lower the voltage to the igniter.

I don't know what your igniter is rated for, but I'll
bet that using 16 volts will be no problem for the
igniter, at all. I don't know if your adapter will
be able to provide the current that the igniter needs.
If you look at the adapter, you should see its current
rating on the label. The other piece of information
needed is the current rating for the igniter. It would
be helpful if you could post those numbers.

Ed