Q:

Arduino - switch control

I am making a balloon cut off mechanism using Arduino. The Arduino uses GPS data to find the height of the balloon. So when a certain height is reached it has to allow current to pass through a nichrome wire to burn the nylon rope.
How do I use Arduino to act as a switch? That is, when a condition is reached, Arduino has to allow current to pass through. Can it be done using Arduino?
Is there a digital switch I can buy and control via Arduino? My search gave me suggestions to use a Triac. Is there a easier way?

A:

Not really a SO question... but I've used this TIP-120 circuit in many projects with success. It's tolerant of abuse (handles high current, etc) and easy to put together with parts from Radio Shack costing a few dollars. (for your usage, the diode is not required).
Turning it on is as simple as digitalWrite(pinNum, HIGH);
Personally, I would use a mechanical solution as a release mechanism rather than trusting the vagaries of heating at high altitude and the higher power reqs.

