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Wednesday, 18 September 2013

Relay on the Pi

It was Martin Oldfield who clued me up on this - you can get a little relay for about £1 that you can connect to a Raspberry Pi's GPIO pins, and use it to control mains voltage at ten amps.

Here's the relay (you can also get two, four and eight channel relays).

Here's the wiring:

    Pi                                          Relay Board

                                                         +-------------------------+  Switched
    --------+                                         |                                 |   contacts
         . o |  <-- 5V ---------      Vcc -- | o                            . |
          . . |                           --- IN1 -- | o                           o | <----
         . o |  <-- Ground - / - GND -- | o                           o | <----
          . . |                        /                 |                                 |
          . . |                       /                 +-------------------------+
         . o |  <-- GPIO 18
          . . |
          . . |
          . . |
          . . |
          . . |
          . . |
          . . |
              |
              |
 
And here's the code to control the relay:

cd /sys/class/gpio
echo 18 > export
cd gpio18
echo out > direction
echo 1 > value
echo 0 > value


Simples! I tried it, and it worked fine.

I think it's pretty obbious how you extend that to control multiple relays.

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