# Engineering help

1. Nov 26, 2009

### gajopo

The application may seem trivial, but I need to control an aquarium powerhead (pump). I'm an elevator adjuster by trade and have no problem understanding schematics and scouring datasheets but am by no means an electrical engineer.

My issue simplified, controllable powerheads cost 8-10X the cost of the same flow 120vac single speed synchronous pumps. Their ac counterparts are simple, two coils, one with a few extra turns to get the permanent magnet impeller to turn in the desired direction. Problem is with the interval timing circuit I am using the causes the pumps to "chatter" upon excitation stressing my much loved salt water inhabitants. Yes I could spend 1500$on Tunze controllable pumps with a controller, but I like the 150$ approach better if possible.

What I would like to accomplish is a circuit that would supply 60hz during their "on" state and 1-59hz during their "off" state, slowing them to near their synchronous stall state (1-59hz, maybe 17hz??...). 60Hz is simple as I am doing that now.

How can I make a 120vac (+- 40v) 1-59Hz power supply? I have been scouring the internet for days and decided to just start posting were someone with the knowledge may see this and give me something I can plug into Electronics Workbenches MultiSim for trial and error.

For those of you who may care, a Hydor Koralia 4 (What I'm using) costs 30$. A Tunze Stream starts at 329$ plus the 12vdc controller. Both pump water, one just capitalizes on control via a large price hike.

Any input is greatly appreciated!
Gary

2. Nov 26, 2009

### Snoogans

When you say interval timing circuit, is it just a circuit to turn them on and off at different times during the day?

3. Nov 27, 2009

### gajopo

Right now I am using 2 .1 to 99 second in-line timers and 2 relays. The pumps are on opposite sides of the tank set at 12 seconds, simulating the ebb and flow found in natural reefs.

4. Nov 27, 2009

### Snoogans

Sounds like a soft starter is what you would need, can't say whether they are available for motors of that size though.

5. Nov 27, 2009

### gajopo

There is my problem. Single phase soft starts require specific motors with special windings, centrifugal switches, capacitors and on...

If I can find a way to make a 120vac adjustable frequency low wattage power supply I can supply on its hysteresis(off) state to slow the pump motor just above stall I will achieve my goal. At least thats my theory!