How can I ignite these three rocket igniters?

[minorwork]

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.

 

[Max CR]

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

 

[Max CR]

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?

 

[minorwork]

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.

 

[minorwork]

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.

 

[Max CR]

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.

 

[Max CR]

Why am I scaring you?

 

[negitron]

You want a circuit similar to this:

http://img141.imageshack.us/img141/9343/rocket1.jpg

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.

 

[minorwork]

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" . 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.

 

[minorwork]

You want a circuit similar to this:

http://img141.imageshack.us/img141/9343/rocket1.jpg

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?

 

[Max CR]

You want a circuit similar to this:

http://img141.imageshack.us/img141/9343/rocket1.jpg

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.

 

[negitron]

Nice. Is that Visio?

Eagle PCB.

 

[negitron]

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.

 

[Max CR]

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.

 

[minorwork]

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.

 

[Max CR]

Now the thing is I want to make this as CHEAP as possible. Can you help me find on radio shack's website thsi capicotor and battery you are talking about? It is very difficuilt to keep looking back and checking to ese what works and what doesnt.

 

[minorwork]

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.

The 2032 delivers more milliamps and so maybe downsize the capacitor?

 

[Max CR]

Ok so I will use those batteries. Now what capacitor should I ues? What i don't understandi s why I am going to use a 3 volt battery if each igniter requires 9 volts to ignite. Even in series, that will only be 9 volts total for three igniters.

 

[minorwork]

Ok so I will use those batteries. Now what capacitor should I ues? What i don't understandi s why I am going to use a 3 volt battery if each igniter requires 9 volts to ignite. Even in series, that will only be 9 volts total for three igniters.

You're scaring me again. Each igniter in parallel will see 9 volts. Should be enough voltage if you can deliver enough amps quick enough to maintain that voltage for long enough to fire the igniter. Ergo the capacitor.

 

[Max CR]

Aright. Now why wouldn't I just use a regular 9 volt battery as the power source? Or two 9 volt batteries?

 

[negitron]

The 2032 delivers more milliamps and so maybe downsize the capacitor?

No, but 2032s will charge the cap faster than the 1216s. This may or may not be important to the OP. If he needs to fire very shortly after connecting, then the higher amperage batteries are more suitable, at the cost of increased liftoff mass.

 

[negitron]

Aright. Now why wouldn't I just use a regular 9 volt battery as the power source? Or two 9 volt batteries?

Weight. Four CR2032s or 1216s weigh MUCH less than even one 9V battery, even the lightweight lithium ones. If weight isn't a concern after all, then a 9V lithium battery will do fine.

I also feel compelled to point out that "cheap" and "reliable," while not necessarily mutually exclusive, are not often considered together in a single design for a reason.

 

[Max CR]

Ok. I will just stick with the 9 volt battery sicne I am not interested in spending any more money. Now, as for the capicotor, you said that i need to have a capacitor rated at 11 amps, I believe.

This one appears to be able to get the job done. What do you think? http://www.radioshack.com/product/index.jsp?productId=2102508

 

[Max CR]

Any ideas?

 

[minorwork]

Ok. I will just stick with the 9 volt battery sicne I am not interested in spending any more money. Now, as for the capicotor, you said that i need to have a capacitor rated at 11 amps, I believe.

This one appears to be able to get the job done. What do you think? http://www.radioshack.com/product/index.jsp?productId=2102508

Negitron suggested a Farad which is a lot of capacitance. Reasonable sized ones are limited to low voltages such as 5 volts or so. Your voltage rating in capacitors is determined by what is in the space between the plates. Too high and there is an arc between the plates and you've a short or if there is enough power you blow up the capacitor. You can tell these because they are swelled up and maybe cracked. I've heard the little ones blow in my computer. Sounded like a black cat firecracker. In the late 90s there was millions of faulty electrolytics let loose and installed. What a nightmare. Hospitals were corrected first but nobody cared about the coal mine or personal computer power supplies. A true pain in the neck for me. And job security.

Here be some http://www.hifisoundconnection.com/Shop/Control/fp/tcat/28042/SFV/30046". You won't like the price or size.

You're on the right track testing a single 9 volt battery. You might consider more than 1 of those capacitors across the positive/negative leads. In parallel mind you. Test. Test. You'll get it.

 

[Max CR]

There just has to be a cheaper alternative to all of this. How about adding three 9 volt batteries in parallel in the circuit? That is where my line of thinking is right now. I don't want to spend anything over $20. As I said before, I was able to successfully do this once before using two batteries in parallel charged at 10 volts with the igniters in parellell also. The only problem with doing this again is that the batteries will not stay at 10 volts because they are not desigend to do so.

How can I work out this situation from here? I have tried putting the batteries in series but that did not work. It seems the batteries have to be in parallel so their amperage will add up but yet the voltage also needs to be 10 volts or above

 

[minorwork]

I'm going to have to pick up one of those disposable cameras and see what it will do. Lots of stuff on YouTube on this. This http://www.youtube.com/watch?v=8XXfEoDIF0Q". Three cameras for $9 from wal mart. Good price. Three hundred volts available from a single AA cell.

Note how taking apart the cameras can get you shocked if you don't discharge the capacitor.

 

[minorwork]

There just has to be a cheaper alternative to all of this. How about adding three 9 volt batteries in parallel in the circuit? That is where my line of thinking is right now. I don't want to spend anything over $20. As I said before, I was able to successfully do this once before using two batteries in parallel charged at 10 volts with the igniters in parellell also. The only problem with doing this again is that the batteries will not stay at 10 volts because they are not desigend to do so.

How can I work out this situation from here? I have tried putting the batteries in series but that did not work. It seems the batteries have to be in parallel so their amperage will add up but yet the voltage also needs to be 10 volts or above

Cheaper, better, faster. Pick two.

 

[Max CR]

Cheaper, better, faster. Pick two.

What does this mean? ...

 

[negitron]

It means you can do something better and cheaper, faster and cheaper or better and faster. But not all three.

It's an old engineering maxim.

 

[minorwork]

What does this mean? ...

This is the engineer's mantra. When management wants something done the engineer presents the three choices to management. Cheaper, faster, better. You can only get two. If the solution is cheap and fast it won't be better. If better and cheaper it will take longer to produce. If faster and better then it will certainly not be cheap.

These be the trade offs that concern any designed product. Where did the mantra come from? I don't know. I think the trade offs are some kind of state law.:

This applies in all areas. Your igniter problem in particular. If a capacitor were in existence that could be the same size as the battery and store the same amount of energy and could drain itself totally in in a second then it would be expensive. If you want the solution now it might be cheap and available from parts you already have but it will not be the best solution.

Clearer now? It is a humorous fact of life. Applies to wives too. Just don't tell mine.

 

[Max CR]

So I just did two tests. All three igniters were in parallel.

For my first test, the two batteries had a voltage of 9.65 volts. They were in series. There was ccontinuity.Only two of the three igniters ignited.

For my second test, the two batteries had a voltage of 9.65 volts. They were in parallel. There was continuity. Again, only two of the three igniters ignited. The same igniter did not ignite.

I am considering adding a third battery to the batteries in series. Thsi would bring the voltage up to about 27 volts. Do you think this would be good enough to ignite the three igniters simultaneously? What I don't udnerstand, is that each igniter seems to require 9.6 volts to igntie. However, they are getting more volts than that and there is still failure. Good it be the amperage that is the problem? Should I put the three batteries in parllel?

What other cost effective solutions could there be?

 

[Phrak]

What is the resistance of your igniters?

 

[Max CR]

0.8 ohms each

 

[Max CR]

Now let's say that I put all of the igntiers in series. There is continuity throughout the series. Does that mean that all three igniters must ignite? Will the voltage and amperage be easily disributed? Is it possible for only one igniter to ignite and two not? I have spent nearly the whole day working on this with no success. This is extremely frustrating.