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Unread 09-02-2014, 23:20
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AKA: James
FRC #2168 (The Aluminum Falcons)
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Re: Need example for using optoisolator & FET

I would suggest looking at using a relay.
  • They don't require a lot of current to energize
  • They provide circuit isolation
  • They can source a lot of current from your supply

It seems like they suggested this as a possible option in their response.
I'm not familiar with the FTC rules myself, so I can't comment to its legality.

Relays can be sourced locally at radio shack. You probably only need a SPST relay.

It looks like the HT SuperPro has 3.3v outputs, so you wont be able to drive the relay directly. Luckily there's lots of circuits online on how to control a relay from a microcontroller. Like this. One modification to the circuit on that page though - I would suggest adding a diode across the relay coil as shown here.

This page will help you pick your R values.

Common diodes 1N4004, 1N4001
Common NPN transistor 2N3904
This relay should work if you're switching 5volts to the LEDs.
This one if you're switching 9volts to the LEDs.
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Last edited by otherguy : 09-02-2014 at 23:57.