Building an Aquarium Feed Button to Temporarily Turn Off Pumps
I’m a beginner reefer, and have been at it for about 6 months. I recently put together a little electrical project to make feeding time a bit more convenient, disabling the pumps for a fixed amount of time, and turning them back on automatically.
Disclaimer: This project involves working with high-voltage electricity. I am not responsible for anything you may choose to do with the information contained herein. Be careful!
My fish tank has a sump and a return pump, so under normal circumstances, water is constantly being pumped into the display tank, which constantly overflows into a pipe that returns to the sump. I also have a powerhead, which creates current around the display tank. Some reefers recommend turning off some or all of the pumps in your system during feeding time so that the food stays in the tank for the inhabitants to eat. I feed pellets and refrigerated mysis shrimp, and have noticed a lot going into the overflow before the fish get a chance to grab it.
The Problem
Until now, to turn off the pumps I’ve had to reach for the power strip I have mounted in the back of my aquarium stand, and remember to turn everything back on after a few minutes.
On several occasions, I’ve gotten sidetracked and left the pumps off longer than planned. I’ve even left the house and worried that I never turned them back on, and had to turn back to double-check.
The Solution
The fix is to add a countdown timer to the outlet that both pumps plug into. Countdown timer switches are readily available at any hardware store, and are the same kinds of electrical timer switches you might find in a sauna, or on the bubble pump on a hot tub.
However, these are for turning something ON for a short period of time, then turning it OFF automatically. We want to do the opposite, so we’ll need to wire up a relay to reverse the functionality of the timer switch. When it’s allowing electricity through, we want the outlet OFF. When the timer runs out, it will cut power to the relay, turning the outlet and pumps back ON. Here’s a digital countdown timer, 120V relay, and outlet, all connected to a three-pronged appliance cable. We can set this whole contraption up in a 2-gang wall box and it will make a nice, neat form factor that will fit into the small space in the aquarium cabinet.
Here’s a crude schematic:
The timer has the normal hot, neutral, and ground, but also has a switched red wire to activate its load. In our case, the load is the relay’s coil.
Note that the hot (black) wire feeding the outlet is connected to the “Normally Closed” terminal on the relay, so current can flow through the outlet unabated until the relay coil is activated.
When you press a button on the timer, the outlet will lose power for the specified duration, temporarily turning off the pumps!
Parts
- 2-gang surface mount electrical box — $10.00
- 8-foot round 3-prong appliance cord — $10.00
- 1/2-inch cord grip conduit fitting — $3.50
- 120VAC SPDT Relay — $11.00
- Enerlites Preset In-Wall Countdown Timer Switch — $21.00
- Decora dual outlet — $2.00
- Decora 2-gang wall plate — $1.60
- Wire nuts, female crimp-on terminals
The most important (and expensive) part is the countdown timer switch, which I liked because it doesn’t use a spring, and has preset buttons for 1, 5, 10, 15, 20, and 30 minutes. The relay I got on Amazon, and the rest was available at my local Lowes hardware store.
Putting it all Together
The style of box I purchased comes with caps for all of the 3/4" conduit ports. I capped all but one, and used the included 3/4" to 1/2" step down to connect my wire grip connector. Be sure to get one that’s appropriately sized for the appliance cord you plan to use. (The rubber ring that grips the cord should be snug so you can pull the cord through, then should grip it tightly once you tighten it.)
I only needed about 2 feet of cord coming from the box, leaving plenty of leftover cable to cut into pigtails.
I installed the countdown timer in the box first, as it is pretty deep and would not allow for any wires or nuts behind it. Then I wired the rest of the circuit. The relay has male spade terminals, so you will need to terminate some 12/14 AWG pigtails with crimp-on connectors to make the connections.
The spade terminals leave some small exposed metal surfaces. Be sure to cover them all with electrical tape so nothing can accidentally short if things shift in the box. Wrap the terminals on the outlet with electrical tape as well.
With all the wires and wire nuts, and the relay, there’s a lot to cram into a tight space. If you lay the relay on its side in the box, it will fit perfectly behind the outlet. You may need to get creative and use every nook and cranny for positioning the bulky wire nuts.
Wow, it really works!
From there, I tested the outlet to make sure I didn’t get the relay wiring backwards (I did on the first try… remember, the outlet is connected to the “Normally Closed” terminal). Then it went in quickly with a couple of screws in my aquarium cabinet. Now I can conveniently feed with peace of mind, knowing I won’t forget to turn the pumps back on!
Thanks for reading, and happy reefing!
