Aquarium Timer

It's the story of building the lighting timer for my small 120 liter fish tank. Just when they said lights should go up and down on schedule I knew it it's not going to happen in my house. Just won't work that way. So I decided to automate it.

I've got excited about ESP8266 and figured that might be a great choice for the next gen timer. It is small, working on 3.3v, allows to connect to my local network to check status and make remote switching if necessary; all in one small body.

Here's the schematics of what I came up with:

220V power comes through J1 and is converted into 5V that is used to feed WeMos D1 Mini and switch the relay module. Since WeMos D1 Mini operates 3.3v, we need to use a NPN transistor as a simple switch. Traditional choice is 2N2222 with a 1kOm resistor in the base circuit to limit the current. We also need a D1 diode to cut out reverse current in the relay circuit. That's all schematically.

The casing was designed in Sketch Up and 3D-printed in three iterations, all due to small errors in measurements. I used PETG plastic as the material and it worked very nicely. Here's the model and the result: