Aquarium (or general purpose) controller


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Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 5857
Posted: 11:17am 03 Mar 2024      

This is my current project between other things. :)

It's a board (designed to fit a CMM2 case) that can be used for general purpose control.

2 DC outputs with ON-OFF-AUTO switches (selectable for 5V or 12V)
-- (intended for white lighting and CO2 dosing solenoid
3 DC outputs
-- (intended for PWM LED lighting)
1 AC mains relay output with ON-OFF-AUTO switching
-- (intended for airstone pump)
2 AC mains relay outputs with OFF-ON switches and a crude form of relay coil monitoring
-- (intended for filter pump and heater)
1 input for DS18B20 temperature sensor

Socket for RTC
Socket for SDcard reader
Audio buzzer
RGB indicator LED on front panel



The idea is that it gets rid of a lot of 13A plugs & sockets, giving easy control of things (like shutting off the filter pump for cleaning) without bothering about wet hands. All switching is at 3.3V or 12V and all the toggles are connected to mains earth.

I couldn't find small mains outlet connectors so I settled for 3.81 pitch pluggable terminals as these are not easy to touch. With hindsight I should have put links on the PCB to disable the relay for any unused mains output, but never mind. The plugs for the mains sockets are screwless types as the wire exits from the back. A bit of heatshrink sleeve should make them completely touch-proof, if a bit lacking in cable retention!

As you can see, this could be used for all sorts of things where you just want a bit of a control system. It wouldn't take much to modify the design if you needed auto control of the two switched mains relays, but I deliberately wanted them safe. The tank can be run even without the Pico if necessary.

Using a Pico W in this would allow me to update the program over Telnet, so no access is needed to the USB connector once up and running. That's one less hole in the box.

The mains connections are reduced from:
modified 6-way extension block
hard-wired 2-pole timer
two 2-way mains adapters
plugs for:
heater, filter pump, airstone pump, CO2 solenoid, RGB light, white light, work light, standby water heater
to
standard 4-way extension block
plugs for:
12V PSU, mains supply, work light, standby water heater