Resun Wavemaker

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Well, with a waveBOX, you only have on and off, no current control.

There are two reasons the 555 timer plus relay doesn't work. Fist, the constant on/off induction will weld shut the main AC relay contacts if you select a relay that's "properly rated". You really have to over-size the relay if you want it ot last on a long enough timeline.

The real trouble though is that AC motored powerheads can/will start in EITHER direction. In order to move enough water fast enough to create a wave motion, you MUST use a propeller type powerhead (like a Hydor Koralia). So if a pump like this starts backwards, obviously the propeller spins backwards and it wouldn't work. To combat this, AC powerhead designers have mechanical stops that physically halt the impeller and force it to spin the other way. Sometimes on startup, you hear a powerhead "chatter". This is the propeller hitting the mechanical stop rapidly multiple times a second. So if you're starting/stopping the motor multiple times per minute (aka 1-2,000 times per day), the mechanical stop and/or the prop will wear out QUICKLY from all that impact. Also, for every time the powerhead chatters, it is NOT pumping, and that will impede/reduce the wave action.

It's been done a few times by folks, most commonly with maxijet mods, and each runs into those problems... Were it that easy, yours truly would have done it a long time ago :)
 
Hum.... Yes, that would be the obvious thing I missed. I assume an oversized relay and a DC pump would be a similar problem?
 
Actually that would work just fine. Basically what the Tunze is... Although I think they use pulse-width modulated FET's, but you could do it with a relay, back EMF might be a problem, but maybe not. See with a DC motor it only goes one-way so you don't have the mechanical problem, there's no need for that physical stop. Only difficulty is if the impeller free-wheels at all on you, you could get some back EMF generated which might damage the relay over time. Could be taken care of with a diode/capacitor bridge though...

Good luck finding an "affordable" submersible DC motor though...
 

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