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Nichrome ignition circuit

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nbabusis01

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I am trying to create an ignition system to launch a rocket from a weather balloon, so I need a system that is reliable, lightweight, controlled remotely (via an arduino relay), and can operate down to at least 0ºC.

I can (barely) get a piece of 36g Nichrome 80 wire to glow red-hot by shorting it across a 9V battery, but it does not work when shorting 9V's in series. Also tried using the same wire to discharge 4700 uF capacitors alone and in parallel without success. What should I do? Do I need to change my power supply or my ignition wire?
 

UhClem

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A 9V battery has too much internal resistance to work. You need a battery chemistry with much lower resistance. Nicad works and can be found in the 9V form factor. LiPo also has very low resistance. Of course both fall off at lower temperatures but I don't think 0C is too low. Testing is of course in order.

Measuring internal resistance is easy. Pull a measured current, measure the voltage drop and apply Ohm's Law.
 

cerving

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A 2S/7.4V LiPo rated at 500 mAH or so should do it, and they're about the same size as a 9V battery. It's lighter too, which is a bonus. You're not going to be able to use a capacitor to light a nichrome wire igniter, it takes too long to heat up... probably 2 or 3 seconds.

Since you're a new member, you might not have heard about the legal issues related to launching rockets from balloons... I don't know if you're in the US, but if you are it's going to be a very uphill battle getting FAA approval for your project.
 

thomas

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I would not use anything else than commercial e-matches, they need less than 1 A to fire.
In the US you might have to use the Firewire ones.
 
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