27 replies to this topic

[pyromaniac303]

says 4,7?F So should be fine. I'm assuming the comma represents 00's

Thanks!

Seems like the 'mu' or micro greek character (which looks a bit like a U with a stick on the front) is not appearing on this site. Micro means a millionth, milli is a thousandth.

I think that especially in europe they use the comma interchangeably with a decimal point, so thats all it means. Should be OK.

Test it with an Ematch though, of exactly the same manufacturer, and batch number as the rest you wil be using.

[pyrotrev]

Head out Tue morn.

Lucky b****r! it's freezing up here. Hope all goes well!

[BrightStar]

I think a few last minute design suggestions might be helpful here!

Just to be clear, a 4.7uF (or 4,7uF) capacitor will not work in the previous suggested configuration, 4700uF might. The 4700uF capacitor will be fairly big - about 18-25mm in length and 16-35mm in diameter. A 4.7uF will only be 6-11mm long and approx. 5mm in diameter.

Charged to 9v, your 4700uF capacitor will store 0.19 Joules of energy. In a commercial firing system, this would be enough to fire 1 or 2 matches, probably not 6. Charged to 18v with two series PP3s, it will store 4 times this much and so might work better.

I would omit the protection resistor altogether, or use one of only a couple of ohms. Yes, this will shorten the life of the batteries with a momentary short circuit when you first connect it, but it will allow the battery to contribute materially to the firing current when the circuit is closed. The internal resistance of the PP3s should prevent any 'reverse current flow'.

Assuming the 18v system, I would wire the e-matches in chains of 3 in series for a loop resistance of about 7.5 ohms per chain of 3. This will ensure that each match gets an equal dose of charge at a couple of amps before they snap. Series wiring of matches only works if they are fairly nearly identical, but the LeMaitre ones should be.

You could wire these two chains to the switch (2 parallel chains, each with 3 matches in series) and it would probably fire all the matches together (see note above about the limitation of the capacitor energy though). For greater reliability, you could use two push buttons. The first would fire one chain of 3, the other would fire the second chain of 3 after you allowed a short charging delay. Without the resistor, and with good fresh alkaline PP3s, the recharge between firings will be rapid (one second or so). Capacitors leak current slightly, so it would be best to put in the batteries just before the performance so they don't flatten over time.



Good luck!

Edited by BrightStar, 12 March 2007 - 08:21 PM.

[cplmac]

I would recommend running them in series. When you shoot a professional shoot and have multiple hits on the same cue you wire it in series. This is basic electric principle, in series the current MUST travel through all the squibs before one fires because it cannot complete the circuit until it does. I don't know if a 9V will do it, but I'm certain that a couple of 9v's will if the run is short. Current will take the path of least resistance, which in a paralell circuit is generally the first squib to fire and cause a short circuit. Good luck!

[pyroptix]

Well the gig was pretty cool.

Tropical island in the maldives, 20 million pound production. We performed our fire shows in between live performances from george michael, J-lo and ricky martin.... for 200 guests.

We were on the final night (of 5) and we found out a day prior that one of the crews responsible for pyro shows had commandered the gerbs set aside for us and used them for another act....

Oh well.... Good to know all the above for next time. Thanks again for all the help.

[dr thrust]

hi just picked up some 47000uf caps going to try them out like the diagram thanks

[marble]

you mean 4700uf right?

Because a 47000uf cap is huge and would take sometime to charge up

[ProfHawking]

Not really.. i have an array of 4 x 12,000uf caps, and it only takes a few secs to charge, assuming your power source can deliver a decent whack of current.

[marble]

you will be changing those 9v batts often then

[dr thrust]

arrrrrrghhhhh cheap pp3,s tried 6 together didn,t even make the nichrome warm,tried the 4700 caps like in the dia,not much happening here, must be a cheapo home made e match prob, where can you get them? estes are pricey,ive got a 12v lead acid batt this works every time with" cheapo homemade e match" , hmm what about those 6 v lantern batts?

[cooperman435]

arrrrrrghhhhh cheap pp3,s tried 6 together didn,t even make the nichrome warm,tried the 4700 caps like in the dia,not much happening here, must be a cheapo home made e match prob, where can you get them? estes are pricey,ive got a 12v lead acid batt this works every time with" cheapo homemade e match" , hmm what about those 6 v lantern batts?

Whats the gauge of your nichrome wire matey?

mines 40swg and a 9v battery will fire an ematch immediately?

[BrightStar]

mines 40swg and a 9v battery will fire an ematch immediately?

Mine using 50swg and a sensitive prime take 1.5v at 1A and pop instantly (about 1/20s) with a single AA battery, very similar to the commercial ones.

[dr thrust]

hi seems to be 28 swg, 0.375mm thats all they had,its not a prob on 12v you can cook toast on it! update ive got some 44swg and some 33swg the 44 seems very thin and is easy to snap when working with it and the 33 works a treat with four aa batts,where can i get some35-40 swg?

Edited by chris m, 12 June 2007 - 05:22 PM.