Controlling Aquarium Power Centre with Arduino?

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stephanie
 
Posts: 295
Joined: Sat Dec 11, 2010 1:17 am

Controlling Aquarium Power Centre with Arduino?

Post by stephanie »

I'm having a stupid moment and can't remember how to do something that I think is very simple...

I have a "Digital aquarium power centre" which is a fancy way of saying, it's a power bar with a digital clock to turn on/off the lighting outlets. Essentially it's like a power bar with a built in Powerswitch Tail. Here's a link to the actual thing if you want to see it: http://www.fishsupply.com/sesu-01692.html

I've taken it apart and removed the digital clock part, which was literally a fully separate part. This leaves me with three wires - ground, Vcc, and Relay. If Relay is tied to Vcc then the lighting outlets turn on. If Relay is tied to ground, or just left floating, then the lighting outlets turn off. Vcc is measured at 1.85 VDC.

The Relay line is just a signal line, it is not actually driving the relay in the "Power Centre" - it's 1.85 vdc and was being controled by a glorified cheap digital-watch-like device. The actual relay inside the power bar is a 24v unit that's driven by its own separate power supply. So I'm not worried about high voltage or high current on that relay control line.

I want to control this with my Arduino (it's a Mega, so running at 5vdc). Right now I'm using an actual Powerswitch Tail but I want to replace that with this other product, for two reasons - a) I have two aquariums so my powerswitch tail is running into an outlet duplexer which I don't like doing, and b) this product has two 'nighttime' outlets that turn on when the light outlets turn off, and I want to utilize them for some moonlighting.

I'm thinking of two ways to make this work.

First, I could tie the "power centre" ground to the arduino ground, and take a digital pin's 5v and run it through a couple diodes to drop the voltage down to around 2v and run that straight into the Relay line.

Second, I could use a transistor "somehow" to take a signal from the Arduino and use that to connect the "power centre"'s own Vcc and Relay lines together.

Any suggestions would be most welcome. Thanks!

-Stephanie

p.s. this happens every time I stop playing with electronics for a few months, all the basics leak out of my head and I have to start over relearning a bunch of seemingly obvious things.

p.p.s. the reason I'm not just using the built-in digital clock on the 'power centre' is that it's a piece of junk, it takes forever to program the weeks' on-off times into it, then randomly resets itself and forgets everything. So it's an ideal candidate for some Arduino magic.

stephanie
 
Posts: 295
Joined: Sat Dec 11, 2010 1:17 am

Re: Controlling Aquarium Power Centre with Arduino?

Post by stephanie »

Finally figured it out myself - the magic words are 'voltage divider'. Two resistors and I can drop the 5v signal from the Arduino down to the 1.8 volts required to switch the relay in the 'power centre'.

Cheers!

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