joe
Posts: 29
Joined: Tue Oct 18, 2011 2:40 pm

Re: Can I do this to a FET?

Fri Dec 02, 2011 9:58 pm

It's been a good few years since I did any electronics, so I'm a bit shaky.

I want to drive some LEDs with a FET, driven off a GPIO pin. I'm going to sink the current through the FET. I would also like to have a manual over-ride switch so I can switch them on myself. I'd like to this so there doesn't have to be power to the controller to do this (so I'm not going to do it by pulling the input high for example).

Is it acceptable to just pull the output down with the manual override? Will it fry the component? Picture attached.

12v rail, 2-ish amps drain for LEDs. This is for a unit which has its own current-limiting resistors.

Cheers!

Joe

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johnbeetem
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Re: Can I do this to a FET?

Fri Dec 02, 2011 10:32 pm

That should work fine. After all, it's how NOR gates work. I would think that the only time something like this is a problem is if the load (in this case the LEDs) is inductive like a motor, in which case you need a flyback diode to protect the FET.

[No warranty is expressed or implied.]

joe
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Joined: Tue Oct 18, 2011 2:40 pm

Re: Can I do this to a FET?

Fri Dec 02, 2011 11:55 pm

Thanks! No, load isn't going to send any nasty surprises back into the FET. Unless something very strange happens...

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liz
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Re: Can I do this to a FET?

Sat Dec 03, 2011 12:01 am

Yeah - looks to me like it should work fine. Get to it!
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joe
Posts: 29
Joined: Tue Oct 18, 2011 2:40 pm

Re: Can I do this to a FET?

Sat Dec 03, 2011 12:05 am

About that...

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