Need a little help on my fish tank

[indeep]

This may sound odd but it somthing ive been thinking of.

Ok here it is

I have a reef tank and want to design a wave maker to help my corals stay happy and fat. Most store bought units make the waves be cycling pumps on and off. These pumps are placed in differnt places in the tank and that causes differnt water flows. "happy Corals"

Know my idea is instead of on off, I want to speed up and slow down the motors. I know dc power this is easialy down but i have 120 volt ac motors, I believe shaded poll the have no run capacitor that is why i say that.

Know i was first thinking of some type of riostat like on a bathfan in a bathroom. That would drop the voltage therefor slowing the motor if i very this between 100 and 120 volts will it kill the motor.

Next i was think of changing the hertz up and down. Im familer with this on big commercal moters but can it be down on little aquairum pumps if so how and where do i find the parts

Also i want the motor to speed up and slow down on its own. The only control i want is how fast it throtles up and down and the min and max speed.

So what do you all think can it be down.
Im handy but havent gotten in to deep on the electronic side, so take it easy on big words

thanks
chris

 

[mechie]

Light Dimmer as Motor Speed Control

I have used ordinary domestic light dimmers on several mains motors in the past -- single speed fans, electric drills (watch the power consumption on this one!) and water pumps, even synchronous motors will slow down (magnetic slip). I have a trailing "dimmer-socket" so I can plug anything with a mains plug in directly and have instant control.

I know this will only allow you to set a constant speed but if the experiment works -- there are ways of electronically controlling the "dimmer" circuit.

Try it and let us know how successful you are.

 

[indeep]

That was my first thought but will the drop in voltage increase the amp load and burn up the motor.

Whats a way to set up the dimmer circuit like im trying to do.

Thanks for the reply

 

[mechie]

Fan-Cooled Motors Need Speed

I haven't had any problems with my experiments - a large Vent-Axia fan has been running at its minimum stable speed for months non-stop without problems (set just fast enough to make sure it doesn't stall). 8)

I reckon that an electric drill will soon overheat due to the vast decrease in cooling fan efficiency; so use it for short bursts only - followed by spells of full-speed-no-load to get some air flow through it. I've still done this and lived to tell the tale :wink:

It's a case of suck-it-and-see; if the motor has a cooling fan then it needs that air flow, no cooling fan then try it, watch the temperature, that's all.

Connect the dimmer in series with the fan/pump/drill motor just the same as you would if it were a light bulb. Unless these pumps of yours are BIG then there should be no problem.

 

[indeep]

No they are little suckers and the sit in the water so the cooling is by the tank water around them.

I guess ill start my tests,

My next question is there a way to control the rpms up and down. what im thinking is to have the motors go from say 75% to 100% in maybe 30 sec then go back down in the same speed or faster. What im looking to control is the rate of increase. "the time it takes to go from low to high" and then to independantly control the decrease "high to low" in the same way. As well as the high and low rpms range.

my first thought was a slow turning motor driving the dimmer but then, that would need a control of some sort. Then i reilized i was thinking in terms of mechanicaly controling it. when made with the right circuitry maybe it could electrically.

Thanks for your time