Simple ATO for Nano/Pico Tanks

I wanted the circuit to be timer based so the caveman drawing is what I came up with. I also worked with alot of parts I had on hand. So basically I use a timer relay to run the ATO pump, the optical sensor triggers a 5v relay to cutoff power to the timer relay which stops the ATO pump. So it is a timed circuit that uses the optical sensor as a failsafe cutoff. On the optical sensor circuit the 4.7k resistor can be changed to increase or decrease sensitivity of the sensor. Once i had it layout on a breadboard and working I transferred the sensor circuit to perfboard.

I used a cheap enclosure to house it all. I added a 120v GFCI outlet on the top lid to plug in the pump I had. Using a rotary tool i cut holes and notches for cables to pass then sealed them with silicone.

Not going to do specifics measurements as tank glass comes in all different sizes. I used 1/8 acrylic for the bracket because its easy to work with and fairly cheap. Cutting the acrylic, mark where you want the cut then using a acrylic cutting tool score the line afew times 4-5. Hold the acrylic on a table with the score slightly off the edge, then gently press down on the acrylic till it snaps creating a clean break along your score marks. After all your brackets are cut gluing is simple and fast. Using acrylic solvent glue like Weld-On #4, apply to one edge of acrylic the press and hold together. Setup time is about 4 mins. Drill a hole thru the base piece of the bracket, I used a 3/8 drill bit then finished the hole with my rotary tool with sanding drum bit( sensor was metric).