Arduino DTMF Decoder and Relay Controller

Another Arduino project I’ve been working on is a DTMF decoder used to control a relay board. Using a ham radio receiver, I can switch lights, radios, computers…anything…on or off from miles away. Here’s the video:


Here’s the wiring diagram. And here’s the Arduino code.

I’m using a Sainsmart 4 relay board, although pretty much any relay board would work. You’ll also need a MT8870 DTMF decoder – these run about $2 on ebay. And of course, you’ll need an Arduino Uno. Again, check out ebay for these as well. The total cost here should be less than $12 and you’ve got a fully functioning radio controlled DTMF relay controller!

Michael Brown, KG9DW, is a regular contributor to AmateurRadio.com and writes from Illinois, USA. Contact him at [email protected].

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