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Airstarting Estes Igniters

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DaveHein

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I plan on building a circuit to air-start some Estes motors. Does anybody have experience with firing Estes igniters? I ran some tests with a 9-volt battery (actually an 8.4 NiMH battery) and it works fine. However, this requires a significant fraction of a second to heat up. I need the igniter to fire in less than a tenth of a second.

I am planning on using a voltage doubler or tripler circuit to charge a capacitor to 16 or 24 volts, which I hope will do the job. Has anybody else done this with an Estes igniter? Any idea on the amount of capacitance needed?

Dave Hein
 

DMcCauley

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I plan on building a circuit to air-start some Estes motors. Does anybody have experience with firing Estes igniters? I ran some tests with a 9-volt battery (actually an 8.4 NiMH battery) and it works fine. However, this requires a significant fraction of a second to heat up. I need the igniter to fire in less than a tenth of a second.

I am planning on using a voltage doubler or tripler circuit to charge a capacitor to 16 or 24 volts, which I hope will do the job. Has anybody else done this with an Estes igniter? Any idea on the amount of capacitance needed?

Dave Hein
Double or Tripler circuit won't work on DC.

You're best bet if you want to up the voltage is a simple stand-alone Booster converter. Texas Instruments makes these and are available as FREE samples. Any boost converter will work, or you could also go brute force and simply chop your input voltage in say 40kHz, and then use some cockroft-walton (CW) voltage doupling circuits and then filter the output of those to get a higher (albeit unregulated) voltage to charge a large cap.
 

DaveHein

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Double or Tripler circuit won't work on DC.

You're best bet if you want to up the voltage is a simple stand-alone Booster converter. Texas Instruments makes these and are available as FREE samples. Any boost converter will work, or you could also go brute force and simply chop your input voltage in say 40kHz, and then use some cockroft-walton (CW) voltage doupling circuits and then filter the output of those to get a higher (albeit unregulated) voltage to charge a large cap.
I was planning on chopping the battery voltage and using two diodes and a cap to double the voltage. This would act as a charge pump for a larger capacitor. A tripler would require a couple of more diodes and caps.

My control circuit will include a Parallax SX microcontroller, which I can use to generate the chopping frequency. The storage cap can take several seconds to charge before the launch, so I won't need very large caps for the doubler/tripler circuit. I haven't thought about about the chopping frequency much, but somewhere around 10 KHz to 40 KHz seems about right.

I am more concerned about the details of air-starting an Estes motor using an Estes igniter. As I mentioned, my goal is to fire the igniter in less than one-tenth second from a capacitor.

Thanks,
Dave
 

jderimig

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I am more concerned about the details of air-starting an Estes motor using an Estes igniter. As I mentioned, my goal is to fire the igniter in less than one-tenth second from a capacitor.

Thanks,
Dave
Are you forced into an Estes igniter? The Quest Q2D2 igniters may fire with just the 9v.
 

Zack Lau

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You might look at the LT 1054 datasheet if your application needs less than 100mA. Alternately, I've gotten significantly higher current with a 555 timer chip driving a 1A PNP/NPN pair.
 

UhClem

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I plan on building a circuit to air-start some Estes motors. Does anybody have experience with firing Estes igniters? I ran some tests with a 9-volt battery (actually an 8.4 NiMH battery) and it works fine. However, this requires a significant fraction of a second to heat up. I need the igniter to fire in less than a tenth of a second.

I am planning on using a voltage doubler or tripler circuit to charge a capacitor to 16 or 24 volts, which I hope will do the job. Has anybody else done this with an Estes igniter? Any idea on the amount of capacitance needed?

Dave Hein
You need to deliver about 4.5A for a tenth of a second. Since the Estes igniter resistance is about 1 Ohm, something in your system is limiting the available current. Likely suspects are battery internal resistance, poor connections, too small/long wires, or the switch.

At 24V it would require a bare minimum (ignoring losses) of 6,300uF to store the required energy. (1/2 CV^2) But even then it might not work. The pyrogen may not like pulsed power and just it blow off the bridgewire without igniting.


The one NiMH data sheet I found that listed internal resistance specified 0.5 Ohm. But it also listed a maximum discharge rate of 750mA. This suggests that a NiMH battery is not the best choice. A Nicad would be much better especially if you could find one of the better ones.
 

DaveHein

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You need to deliver about 4.5A for a tenth of a second. Since the Estes igniter resistance is about 1 Ohm, something in your system is limiting the available current. Likely suspects are battery internal resistance, poor connections, too small/long wires, or the switch.
4.5A for one-tenth second -- that's the information I was looking for. So it seems that a capacitor is pretty much out of the question. I ran a few tests firing the igniter directly off the battery. It works with either a NiMH or Alkaline battery. A 9-volt alkaline battery fires a little quicker than the NiMH, but it still takes between one-half to one second for it to fire.

It appears that the limited current from these batteries is the problem. I measure about 1.7 volts across the igniter leads under a steady-state condition. The igniter has a room temperature resistance of about one ohm. However, at the point of ignition the resistance will be higher due to the higher temperature. The NiMH and the alkaline batteries are probably delivering less than an amp of current.

It seems like the solution to getting a higher current and quicker ignition is to use a Nicad battery, as you suggested. I'll look into this to see if Nicads work better.

Thanks,
Dave Hein
 

DMcCauley

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I was planning on chopping the battery voltage and using two diodes and a cap to double the voltage. This would act as a charge pump for a larger capacitor. A tripler would require a couple of more diodes and caps.

My control circuit will include a Parallax SX microcontroller, which I can use to generate the chopping frequency. The storage cap can take several seconds to charge before the launch, so I won't need very large caps for the doubler/tripler circuit. I haven't thought about about the chopping frequency much, but somewhere around 10 KHz to 40 KHz seems about right.

I am more concerned about the details of air-starting an Estes motor using an Estes igniter. As I mentioned, my goal is to fire the igniter in less than one-tenth second from a capacitor.

Thanks,
Dave
Dave,

For airstarting an Estes motor, all you need is a low current electric match. I've airstarted many ESTES motors (clusters of many) with just simple electric matches. No need for high current igniters or whatever. Just use an electric match like a J-Tek or similar. The fit nicely in both A, B, C, D and E's.
 

DaveHein

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Dave,

For airstarting an Estes motor, all you need is a low current electric match. I've airstarted many ESTES motors (clusters of many) with just simple electric matches. No need for high current igniters or whatever. Just use an electric match like a J-Tek or similar. The fit nicely in both A, B, C, D and E's.
If I understand correctly, I would need a LEUP to purchase a J-Tek. Is that correct? Are there any low current electric matches available without a LEUP?

BTW, I searched around for Nicads, and they don't seem to be as widely available as they used to be. Anybody know a good source for 7.2 volt Nicad batteries. I will also need to get/build a charger. An inexpensive trickle charger would be OK.

Dave
 

Adrian A

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I plan on building a circuit to air-start some Estes motors. Does anybody have experience with firing Estes igniters? I ran some tests with a 9-volt battery (actually an 8.4 NiMH battery) and it works fine. However, this requires a significant fraction of a second to heat up. I need the igniter to fire in less than a tenth of a second.

I am planning on using a voltage doubler or tripler circuit to charge a capacitor to 16 or 24 volts, which I hope will do the job. Has anybody else done this with an Estes igniter? Any idea on the amount of capacitance needed?

Dave Hein
I use Estes ignitors exclusively for my deployment charges, using a single small, low-resistance li-poly cell. It puts out about 3.5-4 Amps, and I consistently get ignition times about 0.2 seconds. Here is a typical plot from a recent flight:



The brown line is related to the voltage upstream of the switch I use for the ejection charge. You can see that the switch closed when the onboard vertical velocity estimate went below zero, and the charge fired right about 0.2 seconds later, based on the axial acceleration and the pressure spike. The second drop in the continuity voltage is when the baro-based apogee detection kicked in and turned on the transmitter.

The energy that went into the bridgewire is I^2*R*delta T, or 3.5^2*0.8*.2 = 1.96 Watt*seconds (Joules). If I were to use 2 of these low-resistance Li-ion cells in series, the voltage would double and the resistance would only go up by another 50 or so mOhms, so the power would go up by a factor of 2^2*(900/950)^2, or 3.8. The ignition time should go down by about that factor, or maybe more, since there's less time for the heat to escape as the burnwire heats up. These cells are 1.2 grams each, by the way, and I share the cell with my transmitter so I basically get this power source for free.

Now let's look at what sort of capacitor would be required to do the same job. The energy in a capacitor is 1/2CV^2, so to get 2 Joules with a cap charged up with a 9V battery, you would need 4/81 Farads, or 50 mF. That's a part that's 1" diameter and 2 inches long. That's on top of whatever battery you're using to keep it charged (typically a 45g 9V or an 8 gram, 12V A23 cell). A 20V solution has a little bit smaller cap, at 1" diameter and 1.5" long, but now you need 2 batteries to charge the cap, in addition to your cap, or a boost converter.

Supercaps store more energy for the same size and mass, but their ESR is so high in the small sizes as to make them useless for firing charges. So if size and weight are the primary factor, firing an ignitor directly from a li-poly cell will run circles around any capacitor solution.
 
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Adrian A

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By the way, you probably want to look into the new Quest ignitors. As an experiment I put one across a little A23 cell (which has a short-circuit current of about 0.4 Amps), and it popped in what seemed to be instantly. The pop was so short (a snap, really) I wonder how they can deliver enough heat to ignite a motor, but presumably they're good enough at that, since that's what they're designed for.
 

DaveHein

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By the way, you probably want to look into the new Quest ignitors. As an experiment I put one across a little A23 cell (which has a short-circuit current of about 0.4 Amps), and it popped in what seemed to be instantly. The pop was so short (a snap, really) I wonder how they can deliver enough heat to ignite a motor, but presumably they're good enough at that, since that's what they're designed for.
Adrian,

I'll order some Quest igniters and try them out. The Quest website says they fire at 120 mA of current, so these seem perfect for my application.

I tried a few experiments to see how long it takes to fire an Estes igniter from of a 9-volt alkaline, 9-volt lithium and a 12-volt car battery. I stepped through a video recording of the firings to measure the time. The alkaline and lithium 9-volt batteries each took about the same time, which was 10 video frames or one-third of a second. The car battery took one video frame, or 0.033 seconds. If I could fly the car battery in my rocket I would have it made.:)

When I bought the 9-volt lithium battery I didn't consider that there are several types of lithium batteries. What kind of li-poly battery do you use? Is it the kind used for RC airplanes?

Dave
 

Adrian A

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Adrian,

I'll order some Quest igniters and try them out. The Quest website says they fire at 120 mA of current, so these seem perfect for my application.

I tried a few experiments to see how long it takes to fire an Estes igniter from of a 9-volt alkaline, 9-volt lithium and a 12-volt car battery. I stepped through a video recording of the firings to measure the time. The alkaline and lithium 9-volt batteries each took about the same time, which was 10 video frames or one-third of a second. The car battery took one video frame, or 0.033 seconds. If I could fly the car battery in my rocket I would have it made.:)

When I bought the 9-volt lithium battery I didn't consider that there are several types of lithium batteries. What kind of li-poly battery do you use? Is it the kind used for RC airplanes?

Dave
That test method sounds good. The kind I use is a 1.2 gram, 70 mAhr (tiny!) cell from all-battery.com.
 

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Thought this would be better in it's own thread - hope you don't mind.

Cheers,
Phil
 

DaveHein

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Phil,

Thanks for moving this to it's own thread. I was a little concerned about hijacking the other thread, which actually started out as a poll.

I looked at the li-poly cells at battery.com, and found the one that Adrian uses. It specifies a max current of 2C, where C is 70 mA (it is also listed as 65 mA in some places). That would make the max current 140 mA. Maybe the actual short-term current is higher.

Anyhow, my current plan is to look into the Quest igniters. I stopped at Hobby Town yesterday to see if they had them. However, they only had the Estes igniters, which I bought to replace the ones I used for testing.

I ordered some igniters directly from Quest, and I should receive them early next week. I'll run some tests with these igniters when I get them, and I'll post the results here.

Dave
 
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stickershock23

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Instead of going for bigger batteries or more voltage. go with DMcCauley's suggestion. use e-matches, they will ignite estes motors no prob and take almost nothing to fire. and fire almost instantly

I have a two stage rocket it has a 9 volt battery and a micro switch. when the boosters ejection charge goes off, it kicks the booster, the micro switch closes and 9 volts goes to fire 4 e-matches they ignite 4 E9's

as for a LEUP yep you need one, but if you plan on going bigger in the future, go get on, its not that hard to get. and is almost a must when flying electronics in bigger stuff.
 

DaveHein

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Instead of going for bigger batteries or more voltage. go with DMcCauley's suggestion. use e-matches, they will ignite estes motors no prob and take almost nothing to fire. and fire almost instantly
...
as for a LEUP yep you need one, but if you plan on going bigger in the future, go get on, its not that hard to get. and is almost a must when flying electronics in bigger stuff.
Thanks for the suggestion. I have thought about getting a LEUP, but I keep putting it off. There's something about having to do the paperwork, the finger printing, and inviting goverment officials into my home that keeps me from getting started on it.

If the Quest igniters work out OK then I'll just stick with them. Otherwise, I'll look into high current li-poly batteries with the Estes igniter. E-matches requiring a LEUP are a distant third option at this point.

Dave
 

DaveHein

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I received my quest igniters today, and I ran a few tests. They will fire off of a 1.5V battery in about one-tenth of a second. A 9V battery will light them in less than 33 milli-seconds.

I also tried a few tests using capacitors. A 220 uF capacitor was able to fire the Quest igniter with a voltage of 6 volts. It did not fire at 4.5 volts. 220 uF at 6 volts works out to only 4 milli-Joules of energy!

So it looks like I'm going to use the Quest igniters to air-start my motors. I'm going to build a small controller so I can first test them out launching single stage rockets. The launch controller will use the same circuitry that I'll use for air-starting later on. I'll test this out at the next club launch I go to.

It seems like the Quest igniter might be good for electronic ejection also. I don't know how they compare to e-matches, but at 4 mJ they don't require much energy to fire them.

Dave
 

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Dave

The Quest igniters are designed to operate at 9 volts because that's what the Quest controller uses. Estes igniters won't work well with a 9 volt alkaline, but the new Quest igniters work just fine. On the the hand, the new Quest igniters won't work with the standard Estes launch controller which uses a bulb that draws 0.25 amps, so they fire when you check continuity!

Estes igniters have a resistance of about 0.8 ohms and an all-fire current of 2 amps. In theory they will fire with a single alkaline battery after a while, but don't rely on it. The Estes launcher is 6 volts so a single igniter would draw 7.5 amps if there was no resistance in the wiring but fortunately there is so the actual current draw is less.

Since the new Quest igniter draw so little current, most timers and altimeter can easily airstart a cluster of at least 7 motors.

Bob
 

Grover

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I would try a 12 v battery from radio shack pt. # 23-144 its lighter.

Also, why 1 tenth of a second, you could probably let both stages coast for longer than that ?
 

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Never seen the new quest igniters in person, I hope they are not as fragile as the "MRC" style igniters they been using (plus they were easy to short too). I would be concerned with using estes igniters, because they too break very easily and are easy to short, and I would be concerned with the vibrations and shocks experienced during flight and dual deploy that the bridge wire may break.
 

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Also, why 1 tenth of a second, you could probably let both stages coast for longer than that ?
I have the same question. Why is firing in 1/10th of a second so critical?

I have read that a short delay after booster stage burnout results in higher altitudes for the second stage. Obviously, you need to fire the upper stage before the rocket starts to lean over.
 

TheAviator

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Never seen the new quest igniters in person, I hope they are not as fragile as the "MRC" style igniters they been using (plus they were easy to short too). I would be concerned with using estes igniters, because they too break very easily and are easy to short, and I would be concerned with the vibrations and shocks experienced during flight and dual deploy that the bridge wire may break.

The new Q2G2 igniters are great. They are 2-lead construction with fully insulated leads up to the pyrogen. They are the BP equivalent of the AT First Fires. AT actually packages them with their 18mm D SU and RMS motors now. Robust, light, low current, yet pack enough heat to light a composite motor very quickly. Extend the leads a bit, and I don't see any reason you couldn't use them on larger composites!
 

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I'll second the vote for the new Quest igniters. I started using those a couple of weeks ago and have had excellent results with the Quest 9V alkaline battery based launch controller.
 

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I recently had a successful ignition of a D-12-3 with an Estes igniter using a fresh eveready 9 volt alkaline battery in my Nike-Ajax 2-stage. The wire from the positive post to the igniter was about 5 inches.
I'd love to try an AT motor in the sustainer. What type of battery will be necessary to fire an AT First Fire igniter?
I've done some research on lithium camera batteries and they are said to be protected from a "dead short" condition. Does this mean they will be unsuitable for firing igniters? I have my eye on a stubby little 3 volt that would be great to use if it will work. Ted
 

bobkrech

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I would try a 12 v battery from radio shack pt. # 23-144 its lighter.

Also, why 1 tenth of a second, you could probably let both stages coast for longer than that ?
Grover

The 23-144 batteries are made from (8) tiny 8 mm button cell batteries connected in series. The 12 volt LR23A type batteries (RadioShack 2300144, 23-144, 2300154, 23-154) use (8) 1.5 volt alkaline button cells, the 9 volt batteries (RadioShack 960-0362, RadioShack Alk-10A, Vinnic L1021) use (6) button cells and the 6 volt type (Gold Peak GP26A) use (4) button cells. They are designed to supply voltage, not current.

The 9 and 12 volt versions are often used with the PerfectFlite MAWD altimeters with a capacitive discharge circuit to fire e-matches that activate in a few milliseconds. A CD circuit altimeter does not have the energy to fire motor igniters that require high current for ~0.1 seconds.

Estes igniters have a resistance of 0.8 ohms and have an all-fire current of 2 amps with a voltage drop of 1.6 Volts. None of these small RS batteries can supply this current. You need a battery that will supply current not voltage. A single 3.7 volt rechargeable LiPo battery or 3 NiMH cells will provide sufficient current.

The new Quest igniter may work with the button batteries, however 6 volt photo-flash battery is a better choice since they are designed to deliver current.

Bob
 

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