that reverse thing happens due to the use of N channel tansistors. In reef-pi UI you can configure each channel as "Active High" or "Active Low", to deal with this exact issue
This is a very good question, let me answer it in two parts:
Interrupts were definitely on my personal TODO list for reef-pi. My top off pump is pretty strong and usually only runs for a few seconds, so real-time responsiveness is important to me. It looks like interrupts are not trivially easy using Go on rpi, but I'm sure we'll get it for v3.
There are couple of implementations out there that we can use to get started with, like this one: https://github.com/davecheney/gpio/blob/master/gpio_linux.go
Light controller (Kessil and Actinic LED strip) is next, followed by pH monitoring and then doser. Light controller guide is already done, its in editorial review stage now
I think I'm going to pause my build until the pH, and doser modules are published. I don't want to have to keep modifying what is there, and there is no rush as the tank is still very much dry. I look forward to the publication of the rest of the guide, and i look forward to continuing to be part of this amazing conversation. All of you guys rock.
So i will not be doing this just because dimming 40% where my lights run to 10% is not really worth the effort. Maybe someday I will look into building my own LED's but for now the built in timer is fine. But if you decide to do this, and someone correct me if I am wrong I would not advise running it directly off the GPIO pin. I would use the following:
The PWM GPIO signal out would go in the 3.3v side with a square wave. Use the buck converter you linked above dialed down to 3.3.volts to supply the upper pictured voltage. D1 would be the OR light controller or where the black wire would connect. The key is to find out what the current draw is so that you can size the transistor and resistor appropriately. If you use the built in OR timers all you need to do is hijack the black wire and run ground from your pi build spliced into the red ground wire of the OR fixture.
If your your lights are anything like mine the clock sucks and never keeps time perfectly. So if you wanted to use the built in timers your brightness level and timer will over time be mismatched. To fix this disconnect the plug on the light. The purple and blue would need to be on a 12 volt relay timer programmed to come on and off at your set times with reef pi. The black wire would go to the same input on the transistor above and the red wire would go to your common ground. Since your clock is the same on both power and dimming you would be matched. Here is more on the OR light using the same basic concept.
Thanks!! Any plans for the body for the pumps?
I need to bookmark this response, but I'm on mobile and can't figure out how.
I think a single cable would be less room for layer 1 failure, but it eliminates the ability to kill a single pump outside of the pi. Either works IMO.I have been brainstorming on this today. I think I am going to use 2.1mm female barrel connectors on the main box and then make a small separate box for the pumps with female barrel connectors as well. You can find different lengths of male power cables all over to connect the two. I also considered RCA cables but think I like the barrel connectors better. I am also thinking of using a single RJ45 cable.
