This project relies on a cheap little $15 feeder that goes by a few names, but is basically only slightly different between brands. After seeing what others had done, I felt that there was a better way to accomplish the goal. The original hack I saw involved using up 3 connections to a controller to get the functionality we wanted, but also requiring the handling of what the device was already capable of doing. For that reason, I decided to give it a shot and come up with my own version.
I took apart my unit and found that the buttons are 4 pole buttons, with 2 common pairs. When depressed, the button makes a momentary connection between the two common pairs. Once I figured this out, I was in business and ready to roll. I confirmed my findings by stripping the ends of a wire strip and shorting the two poles I found on the opposite side of the PCB where the "Feed" button would be on the other side. I then started prepping all my items I would need.
I took some twisted wire pair I had laying around from tearing apart a CAT 5e cable. It's about 3' long. I then tried to figure out where it can be wired up with the device nicely. I found that it was not actually that hard a task, the device is basically 4 components. 1 - the shell, 2 - the display with electronics, 3 - the motor and drum, 4 - the battery compartment.
The battery compartment has a slit on it to separate the batteries that it holds, but is also the perfect avenue to route some wire through.
I tried to find a tool to cut a hole in the bottom of the battery cover where no metal was. I ended up not finding anything, but since it's cheap plastic, I figured, what can go wrong with a screwdriver and a screw to make a hole. I used this to great success, but would recommend the proper tooling for this, as it will just work out better for you.
I then took some 1/4" black techflex and covered the twisted wire pairing so that it looks nice coming out of the feeder. I then routed everything through the hole in the battery compartment and had everything ready for me to make the last hard part, which was soldering to the PCB.
The image above is the techflex covered wire pair that is routed in between the slit for the battery separation on the device. I did this to make sure it all was going to work since the battery compartment slides in and out, and I wanted to make sure it still all worked.
I really need to order myself a holder for these little projects, but basically, I somehow got it done and it worked when I shorted the new ends of the wires 3' away. (Small update, I ordered myself a cheap dremel and soldering holder kit after completing this project, so I might redo it in the future to allow the wire to come out the side or back of the unit instead of the bottom. I found the bottom is fine if you are going to use the included clamp on the side of the tank, but otherwise is inconvenient to place down on a flat surface)
To finish everything up, I went and added easy to disconnect waterproof connectors to the ends of the wire coming from the feeder and then some pick-up wire that I had soldered to the clamps that came with the SW5 module for the Reefkeeper.
I put the thing back together, and it all came together perfectly. The only issue is that with the hole I made for the wire, it does put some stress on the wire when opened. This could've been alleviated if I had found the proper tooling to make that hole a little larger, but since i made this modification, I know not to be too rough on the device when opening that compartment. It definitely does not hinder things in the slightest.
I am happy to say I now have the option of using the built in timer or my controller to operate this feeder, and if I ever decide that I don't want to use either one, I can easily ignore them and just use the other option.
I hooked up the new ends of the wire to my Reefkeeper Elite's SW5 Module. This module has a "Relay" port that is programmable just like any outlet would be. I can use it to schedule a time to feed the fish when I have food in the drum. I also am not using up more power, since the unit is relying on batteries. I also still have full control over the unit as can hit the "Feed" button to my hearts delight whenever I feel like feeding the fish.
Overall costs, well, that's a bit tricky. So the unit itself is around $15. I had my soldering iron and wire available to me already, so that wasnt an added cost