Relays

Technical discussions around xCORE processors (e.g. General Purpose (L/G), xCORE-USB, xCORE-Analog, xCORE-XA).
Gilbert
Newbie
Posts: 1
Joined: Fri May 20, 2011 5:24 pm

Relays

Postby Gilbert » Fri May 20, 2011 5:34 pm

Hello,

A question from on non-electronics orientated person:

I want to be able to switch a small 12v motor on and off using an XK-1. So, I need a relay, right? But what sort? I know what my load voltage, current, throw type and so forth need to be but I'm having trouble finding something cheap that will switch using an xmos pin.

They all seem to need 200+mW at 3V. I've read that an L1 can supply 4mA at 3.3V which means 13mW, right? Or wrong? Or do I need something other than a relay.

Advice appreciated,
Thanks.
User avatar
Bianco
XCore Expert
Posts: 754
Joined: Thu Dec 10, 2009 6:56 pm

Postby Bianco » Fri May 20, 2011 5:50 pm

You cannot directly switch a relay from an XMOS pin.
You will need a transistor and a diode.

See

Image
Corin
Experienced Member
Posts: 66
Joined: Fri Dec 11, 2009 3:38 pm

Postby Corin » Fri May 20, 2011 6:04 pm

Why not use an N-channel FET?

The XS1 can drive the gate of the FET (assuming it's gate capacitance is not too large). You would connect the +12V to one side of the motor and connect the other side to the drain of the FET. The source of the FET should be grounded.

Cheers,
Corin

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