I have a small IoT project where I want a network enabled electrical relay. I do not need full network plug nor linux on it. It just should be small and cheap. I feel smart enough to write a small http server in C/C++ (if required) to change the state of the relay. I searched of cause the web and found the almost matching dublicate Cheap IoT microcontroller with PoE

However this is much bigger then what I have in mind. I want a small board with 6 skews to mount the wires (2 or more replays would be fine too). I want to control a device for with less then 25V (I'm not sure but very likely 12V DC). However I do not want to write the TCP/IP stack by my own.

Any ideas?

  • This might almost be better asked at hardwarerecs.stackexchange.com However, the TCP stack makes it eligible here. There's a lot of crossover, so if you don't get an answer here, try there after a week or so.
    – Mawg
    Jun 12, 2018 at 11:57
  • Can you help us by defining "small" and "cheap"? These are relative terms. Must it be POE? Would you accept WiFi, with a power source (USB or other)? Is the power for the controlled device also coming from the board which you seek?
    – Mawg
    Jun 12, 2018 at 11:59
  • I bought already a POE switch for a different device and I have there no room for more cables. Cheap let's say less then 50€ it should the longest side should be smaller then 55mm including an case if required.
    – rekire
    Jun 13, 2018 at 3:44

1 Answer 1


Well, I am a big fan of the Omega 2, which is not much bigger than a full size SIM card or SD card. It runs Linux, so there is your TCP/IP stack.

enter image description here

It has a good spec and will set you back a whopping $13.

128MB Memory
32MB Storage
USB2.0 support
2.4GHz b/g/n WiFi
3.3V Operating Voltage
18 GPIOs
Support for UART, I2C, SPI
MicroSD slot

Just by coincidence, I received their newsletter about 20 minutes ago and it describes a PoE project.

That will set you back another few bucks, so I will leave it to you to decide if it is "cheap". Hope this helps.


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