How can I ignite these three rocket igniters?

  • Thread starter Max CR
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Radio Shack used to carry the capacitor. That's where we got them for a while at the mine. Used them to buffer the 24 volt power voltage levels in an RS-485 network system that monitored carbon monoxide levels on the belts. A micro computer and co sensor every thousand feet and we had about 6 or 7 miles of belt. The analog sensor like steady voltage and the digital drivers pulled a lot of current when driving the line with the data. To steady the voltage for the analog sensor and its analog to voltage converter in particular the capacitors across the 24 volt DC line worked beautifully. Had a capacitor at each microcomputer every thousand feet.

Hey I just found the capacitor. I was wrong on its capacity. These be the right ones. Apologies. http://www.radioshack.com/product/index.jsp?productId=2102508". It be smaller.
 
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You lack amps, not volts.
 
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Ok. Now the only problem with me using the capicitor is that I am unfamiliar with how they work. How many capicitors should i put in the circuit in series? On the capicitor, how do I charge it and place positive and negative no both ends of it?

Thanks
 
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Also, something that is really worrying me is a problem with putting the igniters in series. If I put the igniters in series, and the circuit is turned on, I am worried that the first igniter in the series will ignite and then burn out too quickly. If it burns out too quickly, it will prevent the other igniters from igniting. After the gun powder on the metal wires is done burning, it causes the clips to break. This may happen to the first one and prevent the other ones from igniting.
 
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Also, something that is really worrying me is a problem with putting the igniters in series. If I put the igniters in series, and the circuit is turned on, I am worried that the first igniter in the series will ignite and then burn out too quickly. If it burns out too quickly, it will prevent the other igniters from igniting. After the gun powder on the metal wires is done burning, it causes the clips to break. This may happen to the first one and prevent the other ones from igniting.
Test on the ground. The igniters may be too expensive to use for tests. Get some individual strands of wire from some scrap electrical cord. Get yourself three individual single wires. They'll be about the sized of a hair or smaller. Hell, use a strand from some steel wool though they are pretty brittle and break easily. We used to take such a little piece of wire in a slit on a paper match head and attach them to a piece of paper clip that had been pressed with some lineman pliers to leave a cross check pattern so the thin igniter wire itself would hold on, put some tape around the thing to hold it together and we had an igniter. Estes' were more reliable though. Wire three in a series circuit with bigger wire between them and test away.

Maybe a single 9 volt battery will do the job if you have a capacitor (that 4700 mfd one) attached across the leads. A capacitor reads as an open circuit after it is charged. Take two pieces of aluminum foil and put a sheet of wax paper between the aluminum sheets. You have made a capacitor. The electrical energy is stored in the electrical field between the two sheets. When you attach the + side of the battery to the positive side of the electrolytic capacitor and the negative side of the battery to the negative side of the capacitor, then the battery will charge the capacitor to the voltage of the battery. Now you have something like that balloon on a set of bagpipes where you store the air that you blow out so that you can breathe in between and still have air pressure to sound the reeds.

Another way to see a capacitor. You have a little air pump that plugs into the cigarette lighter of your car. This will be the equivalent of your 9 volt battery. This pump/battery can deliver a little bit of air/amps until it maxes out to its capacity of 150 psi/9 volts, but this takes a long time. What we need is a "lot of air all at once at the maximum pressure"/"a lot of amps all at once at the maximum voltage." So we make a storage device. For the air we use a tank. For the battery we use a capacitor. The 9 volt trickles into the capacitor enough amps that when released all at once will be more than enough to heat all the igniters in the circuit simultaneously to ignition temperature. Equal amps flow in each load in a series circuit. You put enough amps and voltage simultaneously at the igniters and all three will heat up as one. Test this with the cheap little wires suggested.

If 9 volts is enough voltage to set one off, then you need, for the series enough amps/current fast enough to keep the voltage levels up long enough to get all three to ignition temperatures. A 9 volt battery can only deliver so many amps to a load in a given amount of time because the generation of the amps is chemical and is a high resistance source itself since the current sees each of the little cells as a load too. This generates heat in the battery itself in a high load condition. Short out the leads of a 9 volt battery and you'll feel the battery get hot.

The capacitor stores amps if given time to charge to whatever voltage is powering it.

You may be able to get away with a 1.5 volt battery. Consider that the disposable cameras at the drug store use just such a power source to generate 300 volts to flash a strobe. Lookout with these. They can bite if they don't have a bleed-off resistor! Test, Test.

What happens if you have a 9 volt battery with a capacitor across the leads. The battery lets a smaller flow of electrons into the capacitor over a longer period of time so that when we need a lot of electrons to flow in a short period of time we now have, with the capacitor, a large easily moved supply of electron at 9 volts that can flow with little resistance to our igniter load. Test.
 

negitron

Science Advisor
841
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No. Capacitors DO NOT store amps. They store energy. Period. How many amps you can get out of a cap depends entirely on the voltage it is charged to (which will be your supply voltage) and the resistance of the load, assuming no reactive characteristics--for a very long wire there will be an inductive component which will further limit your maximum current but since this is going to be mounted directly on the rocket close to the igniters, it's not an issue here. If the igniters require a minimum of 9.6 volts to ignite properly, charging a cap with a 1.5 volt battery will NOT work. You still need to charge your cap with a minimum of 9.6 volts. And if you have them wired in series, you need 9.6 x N volts, where N is the number of igniters in the series.

Also, contrary to the linked article, a a parallel connection does NOT require more energy to fire a given number of igniters; the amount of energy is EXACTLY the same in either case. Parallel requires more current, series requires more voltage.
 
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http://electronics.howstuffworks.com/framed.htm?parent=capacitor.htm&url=http://micro.magnet.fsu.edu/electromag/java/capacitor/"

From the same site.
Like a Water Tower
One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way and can then release them later.
 
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No. Capacitors DO NOT store amps. They store energy. Period. How many amps you can get out of a cap depends entirely on the voltage it is charged to (which will be your supply voltage) and the resistance of the load, assuming no reactive characteristics--for a very long wire there will be an inductive component which will further limit your maximum current but since this is going to be mounted directly on the rocket close to the igniters, it's not an issue here. If the igniters require a minimum of 9.6 volts to ignite properly, charging a cap with a 1.5 volt battery will NOT work. You still need to charge your cap with a minimum of 9.6 volts. And if you have them wired in series, you need 9.6 x N volts, where N is the number of igniters in the series.

Also, contrary to the linked article, a a parallel connection does NOT require more energy to fire a given number of igniters; the amount of energy is EXACTLY the same in either case. Parallel requires more current, series requires more voltage.
You are exactly right about the capacitors storing energy. So do batteries. The capacitor has little internal impedance compared to the chemical battery. Also the capacitor is passive and the battery is an active energy source.

I had wondered myself at the link saying that about the series requiring less energy than the parallel.

Do you agree that the series circuit is inherently more reliable given an adequate power source? I think so given that an open in one igniter would not prevent the others from firing. An unacceptable situation I believe.

I had speculated that the flash unit in a disposable camera could provide enough voltage but I'm not clear if there would be enough current. What are your thoughts on that?
 
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negitron

Science Advisor
841
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Do you agree that the series circuit is inherently more reliable given an adequate power source? I think so given that an open in one igniter would not prevent the others from firing. An unacceptable situation I believe.
IF the igniters fire before opening, then series would be better for those reasons. I'm not familiar enough with the ones the OP is trying to use to state that's definitely the case, however. Perhaps an experiment is in order.

The problem with series is that, as described above, you require 9.6 volts per igniter--really, you need a specific current to ignite them, but if you need 9.6 volts to provide that current for one igniter, then for 3, you'll need 28.8 volts. The problem here is that 30 volts worth of batteries is heavy; not something you want in a rocket where mass is absolutely critical. It wouldn't be a problem for a ground-based system, since you can hook up as many batteries as you need. But in a rocket, you need to minimize the mass of the infrastructure so you can maximize the payload.

Now, one thing you can do is something akin to what happens in a camera flash you mentioned earlier. The 1.5 volts DC from the battery is converted into a high-frequency AC, which is then kicked up to a higher voltage with inductors, converted back to DC and stored on a high-voltage capacitor. But, this is probably needlessly complex and beyond the OP's capabilities (no insult to him intended). I say if due care is used in making the connections and each igniter is tested individually prior to installation, parallel is the way to go. You can store your 9.6 volts from a set of lightweight Li cells (I suggest coin cells, since they're small footprint and this will essentially be a single-use application) on a high-density cap, as you suggest, and discharge it through the igniters; this should work fine, assuming that the quality-control in manufacturing the igniters is good enough to ensure they're all within a few percent of each other for resistance.
 
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IF the igniters fire before opening, then series would be better for those reasons. I'm not familiar enough with the ones the OP is trying to use to state that's definitely the case, however. Perhaps an experiment is in order.

The problem with series is that, as described above, you require 9.6 volts per igniter--really, you need a specific current to ignite them, but if you need 9.6 volts to provide that current for one igniter, then for 3, you'll need 28.8 volts. The problem here is that 30 volts worth of batteries is heavy; not something you want in a rocket where mass is absolutely critical. It wouldn't be a problem for a ground-based system, since you can hook up as many batteries as you need. But in a rocket, you need to minimize the mass of the infrastructure so you can maximize the payload.

Now, one thing you can do is something akin to what happens in a camera flash you mentioned earlier. The 1.5 volts DC from the battery is converted into a high-frequency AC, which is then kicked up to a higher voltage with inductors, converted back to DC and stored on a high-voltage capacitor. But, this is probably needlessly complex and beyond the OP's capabilities (no insult to him intended). I say if due care is used in making the connections and each igniter is tested individually prior to installation, parallel is the way to go. You can store your 9.6 volts from a set of lightweight Li cells (I suggest coin cells, since they're small footprint and this will essentially be a single-use application) on a high-density cap, as you suggest, and discharge it through the igniters; this should work fine, assuming that the quality-control in manufacturing the igniters is good enough to ensure they're all within a few percent of each other for resistance.
I agree with everything you've said. Seems a waste to haul weight of the batteries if after they've ignited they have any capacity left. I think a properly sized capacitor would be lighter. But, yeah, you got a bit of figuring and/or grunt work testing to determine if one of those 4700mfd's would do the job. The coin cells. I wonder if they would weigh more than the capacitor? The 35 volt cap should not breakdown at 28 volts. That is what the DC power supply sourced for the carbon monoxide detection system I am familiar with.

I did some shot firing in the mine too. Some. We wanted to get home early so we set off a few (quite a few) more than the 20 at one time. We went into overtime putting back up the ventilation stoppings and doors we blew down.
 
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Ok. Now, negitron, you are saying that I need to place the batteries in series. I have three igniters. So I need 3 igniters x 9.6 volts = 28.8 volts of electricity. That would mean I need 3 batteries each charged to about 9.5 volts, correct? The batteries need to be in series correct?

I also think it would be best if I had the igniters in parellel. I would rather have one rocket engine go off than just none of them. But that is what I think. Let me know what you think.

I am also going to be considering capicotors, minorwork, I am just interested in looking into using the 9 volt bateries for the time being because that is what I have readily available.

Thanks
 
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Here is the catch. I was able to sucessfuly do this once before. I used two 9 volt batteries charged at 10 volts. The two batteries were both in parallel. The three igniters were in parellel. Since it is impossible for me to maintain a charge of 10 volts in a battery because the voltage drops, it seems to me that I need to have two batteries in parallel, then one battery in series. This will bring the voltage above 10 volts. Also, my understanding is that when batteries are in parallel their amperage is added. Therefore, wouldn't that bring the amperage in the circuit to double since there are two batteries in parllel. Also, that would bring the voltage to double since one of the three batteries is in series.

Does thsi seem like it will work?

Does that seem to be good?
 
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Ok. Now, negitron, you are saying that I need to place the batteries in series. I have three igniters. So I need 3 igniters x 9.6 volts = 28.8 volts of electricity. That would mean I need 3 batteries each charged to about 9.5 volts, correct? The batteries need to be in series correct?

I also think it would be best if I had the igniters in parallel. I would rather have one rocket engine go off than just none of them. But that is what I think. Let me know what you think.

I am also going to be considering capacitors, minorwork, I am just interested in looking into using the 9 volt batteries for the time being because that is what I have readily available.

Thanks
Sure Max. If you'd rather 1 than none fire then parallel igniters be the way to go. Still, strive for all. Those lithium button cells, or any lithium cell is pretty potent for a single cell. I broke a AA size open and thought the thing would never quit smoking. With more than one you have potential trouble spots in the connections between the cells. Open or high resistance connections are the bane of electrical fault finding. Shorts usually show up vividly and are not hard to spot.

When I said igniters in series was better there was the implied qualification that none going off is better than some going off. An off course trajectory might be undesirable and result from partial ignitions. I was thinking in terms of safety. I don't know what you are up against in that regard. Consider a breakaway on launch or just prior to lauch power up for your igniter's power supply. I don't think I'd want the thing igniting while I'm prepping the first stage. Consider worst case losing of an eye and prepare accordingly. My brothers and I lit off an Estes Gyroc with a booster engine once. The enormous acceleration left the big fins on the launch pad and the remains hauled *** for 500 horizontal feet while maintaining an altitude of 5 feet. Took about a second to do all that. If it had come at us, well, things could have been bad.
 
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Here is the catch. I was able to sucessfuly do this once before. I used two 9 volt batteries charged at 10 volts. The two batteries were both in parallel. The three igniters were in parellel. Since it is impossible for me to maintain a charge of 10 volts in a battery because the voltage drops, it seems to me that I need to have two batteries in parallel, then one battery in series. This will bring the voltage above 10 volts. Also, my understanding is that when batteries are in parallel their amperage is added. Therefore, wouldn't that bring the amperage in the circuit to double since there are two batteries in parllel. Also, that would bring the voltage to double since one of the three batteries is in series.

Does thsi seem like it will work?

Does that seem to be good?
You're scaring me Max. That single battery in series ain't gonna' like having double amps going thru it.
 
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I understand your point and have taken it into consideration. First, I want to do a test to see if I can ignite all three igniters by putting the igniters in parallel, two batteries in parallel, and one battery in series. Do you believe this will work?

If only one of the three engines go off that will be ok because the engiens will be so closely pact together that just havign one of the engines go off would have been safe to begin with.
 
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Why am I scaring you?
 

negitron

Science Advisor
841
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You want a circuit similar to this:

http://img141.imageshack.us/img141/9343/rocket1.jpg [Broken]

The 4 lithium batteries charge the cap to 12 volts at their leisure. When switch S1 is closed, the cap discharges through the igniters in parallel (represented here by 3 resistors). Now all we need to do is choose a capacitor with sufficient energy storage to reliably ignite them.
 
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Why am I scaring you?
Multiple connections. Double amps from parallel batteries pushed thru the series single battery. Unfamiliar with capacitor function. Willing to tolerate one engine fire when three is called for. I hope you take movies. But you said the magic word. Test. Test three times. The first might be a fluke. If you can get three tests in a row to ignite three igniters then you probably have something good.

See how much these look like my match head igniter? http://www.hobbylinc.com/rockets/info/rockets_igniterinfo.htm" [Broken]. Yeah, testing is grunt work. If you can make your own igniters reliable enough you might save some money for testing purposes but probably at the sacrifice of reliability. I was most apt to break the high resistance home made thin bridge wire shown in the link.
 
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You want a circuit similar to this:

http://img141.imageshack.us/img141/9343/rocket1.jpg [Broken]

The 4 lithium batteries charge the cap to 12 volts at their leisure. When switch S1 is closed, the cap discharges through the igniters in parallel (represented here by 3 resistors). Now all we need to do is choose a capacitor with sufficient energy storage to reliably ignite them.
Nice. Is that Visio?
 
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You want a circuit similar to this:

http://img141.imageshack.us/img141/9343/rocket1.jpg [Broken]

The 4 lithium batteries charge the cap to 12 volts at their leisure. When switch S1 is closed, the cap discharges through the igniters in parallel (represented here by 3 resistors). Now all we need to do is choose a capacitor with sufficient energy storage to reliably ignite them.
Ok. Now what lithium batteries should I use? Would this one be good? http://www.radioshack.com/product/index.jsp?productId=2062109

Would this capictor get the job done? http://www.radioshack.com/product/index.jsp?productId=2102508

I need four of these lithium batteries and one capacitor, correct?

Thanks to both of you for your help.
 
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negitron

Science Advisor
841
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Ok. Now what lithium batteries should I use? Would this one be good? http://www.radioshack.com/product/index.jsp?productId=2062109
Those will do, though you can most likely get away with using the smaller CR2016 or the even-smaller CR1216 size; since they'll be charging the cap, instead of firing the igniters directly, they don't need to source a lot of current although it may take a minute or two for them to fully charge the cap. As for a capacitor, you want a high-density type with capacitance in the Farad range and a minimum working voltage of around 15 V. It won't be very cheap (and definitely not available from RadioShack), however if you can recover it intact, it can be re-used indefinitely.
 
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Do either of you have an AIM address? I am literally sitting at the comptuer waiting for a response. I would like to finish this up. Thank you.
 
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Ok. Now what lithium batteries should I use? Would this one be good? http://www.radioshack.com/product/index.jsp?productId=2062109

Would this capictor get the job done? http://www.radioshack.com/product/index.jsp?productId=2102508

I need four of these lithium batteries and one capacitor, correct?

Thanks to both of you for your help.
As for the battery you've picked one that delivers smaller current. I believe negitron called for this one: http://www.radioshack.com/product/index.jsp?productId=3256678"You might test the smaller 2200 mfd. Smaller in size is better for your application I'm thinking. I used both in varying situations in the mine.
 
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