Aquarium (or general purpose) controller

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Joined: 05/10/2019
Location: United Kingdom
Posts: 5857
Posted: 02:18pm 10 Apr 2024      

It's up and running.  :)

Things I had "fun" with....

1) The white tank light
This is a 5V bank of LEDs, sealed, with internal resistors that I can't get at. When using a ULN2003A with PWM to drive them there is far too much voltage drop to get a decent light. Inside the controller they are powered from the 5V supply. I've improved them *a lot* simply by connecting a mosfet in parallel with that channel of the ULN2003A, which is now not doing much. The difference in light output between PWM max and switched to full isn't worth bothering about.

2) The stability of the 5V rail leaves a little to be desired.
The switcher (from the main 12V supply) is supposed to be 4A rated but I think it needs a minimum load to be happy. Putting a load resistor on seems to have helped.

3) The connectors for mains voltage devices (heater & filter pump)
These are actually incorrect and there is a risk of shock if they are unplugged. You do need small fingers though. Unfortunately I couldn't fond PCB mounting female connectors small enough. The cable-mounted female connectors were intended to have heatshrink shrouds to give some cable protection and overall insulation but I discovered that I have no heatshrink that will do the job. :(

4) The Pico W
This has been driving me nuts. Eventually I swapped it for a YD-RP2040 and gave up on the wi-fi side for the moment. It's far too unreliable, with all sorts of reboots and sometimes stupid watchdog timeouts for apparently no reason. Even telnet was almost useless until disabled the HTTP server. The latter crashed most of the time if I sent it messages from the PC browser. At least I allowed a RTC connector on the board. :) I have to set times etc. using a USB lead, but that rarely changes.

5) The RGB LED
Not really a problem, but the three colours have different sensitivities so using max PWM on all three doesn't give a sensible white. I got round it very easily as I wanted a dim green for normal running and the blue was too bright so I used PWM on those two and trimmed things.

6) I squeezed a mains fuse in, adjacent to the board and under its own cover. :)

Then there was fun with the CO2 generation before I eventually gave up and bought a Sodastream cylinder, an adapter, a proper regulator and a solenoid. It's worth doing it that way and I can now tune it down to one bubble per 5s, which is very low. Time switching is automatic, of course.

Water quality is now good and the system seems to be cycled ok so I'll be putting fish in very soon now (possibly this week).