You can use these Arduino controlled relays modules for all sorts of local or remote switching for your radios, antenna and other things.

Poking around online last fall, I came across some interesting modules from China. Basically, I discovered a whole series of modules providing Arduino controlled relays. I found these modules in various configurations including 1, 2, 4 and 8 relays (as shown above.)

These use SPST (single pole, single throw) relays, typically the Songle ISO9002 running on 5 volts. If you read the data sheet, you will find that you can use these relays for switching DC and AC at 10 amps, or small signal RF at lower frequencies. My initial thought was to try using these Arduino controlled relays for switching antennas and filters between my various receivers.

I also found these relays have a decent life expectancy of over 10,000 operations, and should also work outside and down to -25°C.

Since Sainsmart had some promotional pricing, I bought a few of their 4 and 8 relay modules online. Some initial testing showed me that these worked fine. I managed to get each module for around CDN $10, which is way cheaper than I could build one myself.

Out of the box, you just connect Arduino digital output pins and five volts to the module. The drivers require 10-15 mA per relay, which is well under the current source limitation of an Arduino Uno or Mega.

Arduino Controlled Relays – Under the Hood

I found the great thing abut these Arduino Controlled Relays modules is the inclusion of optocouplers. This means with a bit of thought, I can completely isolate the relay switching from the Arduino microcontroller.

The best way to do this is provide a separate 5VDC power supply for the relays. You can accomplish this by removing one jumper on the boards.

Arduino control is easy to do. You normally hold the GPIO pin high, and then lower it to activate the relays in any combination you desire.