So, last month I picked up a 3 head peristaltic pump and motor in preparation of setting up an automatic water change system. I almost have everything I need to get this up and running. The three head pump is nice because they are all on the same motor meaning they should all get the same exact flow rate when it runs.
Details on this type of system are here:
http://www.reefcentral.com/forums/showthread.php?t=2349824
Today I ordered a 24V solenoid valve with 1/4" quick connects. I will tee off my RO/DI output and this will open up the connection upstairs to fill my ATO reservoir. I'll use the RO/DI pressure to get the water upstairs instead of using a seperate pump.
I also decided to set up my 10G QT tank with the third head on the ametek pump. Even if I'm not actively QT'ing anything, I can use it for rinse water

i figure long term it would be better for all the heads to have the same amount of wear. Initially I was going to take one of the heads off. Still not 100% on this yet.
It would work like this: pump head 1 will drain water from DT to QT, head 2 will drain QT to house drain and head 3 will send new SW to DT.
Thursday I received my second ReefAngel which I'll use to manage all this and eventually my SW mixing. I will be using a 5V power supply connected to an outlet on the Reef Angel upstairs to a relay downstairs which will be connected to one of the float switch ports. If this input is not "active" i will not run the RO or the AWC. This way if I'm doing any maintenance or any alarms happen to the tank upstairs, i can immediately abort everything i need to downstairs.
I will also have a float switch in the salt water reservoir that will be connected to the RA so when that flips the AWC will get disabled and I'll send out an alert.
For the RO I will be monitoring the water level in my ATO reservoir from my Mac. When it gets to lets say 25% I'll have a cron job to let the downstairs RA know to open the solenoid for an hour... That should bring it to a target of 75%. If the % goes higher than 90% for some reason I'll have the upstairs controller deactivate the 5V signal and send me an alarm. These numbers are all theoretical so I'll have to tweak once its all in place.
The relays that will control the Ametek pump and the RO solenoid will both be powered by the same 24V power supply which will also power the pump and the RO solenoid. The relays have a low voltage trigger which will be activated separately by a 5V signal from the downstairs RA. This will give me endless scheduling flexibility and the capability to change on demand how much water to change and how long to run the RO for. Right now the target will be to change out 1 gallon per day. I'll need to run the Ametek pump for an hour at full speed to get that. Broken down hourly thats like 2.5 minutes every hour.
I am planning on adding a PWM motor controller on the pumps to slow it down since they are pretty noisy. So at half the RPM it would be 5 minutes every hour. That part is on the slow boat from China (estimated for an april delivery...ugh!!)
I have a bit of programming to do and a lot of wiring and still waiting on some parts to make it all happen but I'm getting closer

Just thought I'd share what I'm currently working on...