I am building a high altitude balloon and I need another way of bringing it down besides the balloon popping. I would like to regulate a battery pack with the GPIO on the Pi in order to heat a nichrome wire, severing a rope. The rope will not be super thick (< 1/4" diameter).

I am not sure what kind of batteries I would need to do this and I'm not sure how I can control the batteries with the GPIO. Information on the type of batteries I am going to need to sever the rope, how to control the batteries, and types of rope is greatly appreciated.

  • 2
    You need to research further. May I point out that the Raspberry Pi is almost irrelevant to the question. – joan Aug 1 '16 at 7:03
  • You should first determine how much current is required. This will help select the suitable components – John La Rooy Aug 1 '16 at 7:04
  • This is effectively a duplicate of the (closed) question here, which includes a connection diagram for a circuit which heats up wire. Per other comments, the specifics of the required supply are dependent on the makeup of your wire. – goobering Aug 1 '16 at 9:37

How about this recent post to hackaday?

https://hackaday.com/tag/foam-cutter/

You could easily control the circuit with a suitable FET. I'd just be worried about shutting it off before you burn up something else. You may want to consider another material for your rope that is more conducive to gravity-driven hot wire cutting.. obviously test this out before launching into space.

Try using a high-power NPN-transistor, then you can control the output to the wire through PWM. If you want to give this a try I can make a schematic for you :)

  • 1
    A few more details would help here like the schematic you mention and a suggested part number etc. – Steve Robillard Aug 9 '16 at 23:38

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