Slow down a pump

[Tim C]

I have a small water garden with a 12 volt, 5 watt pump for the fountian.  The pump perfoms a bit more than I like and want to slow it down a bit as it sprays the water out of the poind.  I have this on a solar panel and battery vs standard house power.  Could a standard 120 volt dimmer switch do the trick?   Thank you for any and all help.

[kitno455]

sure, thats one way, provided that the dimmer uses resistance instead of a zero crossing detector (i.e. a cheap one will work, an expensive one that can run floros wont) you will be turning some of your output into heat, so it will drain your battery more than the right sized pump, but no more than the pump itself does without the resistor.

you may want to look into home-built PWM controllers for computer case fans. they may cause your pump to chatter so you would have to experiment, but they have the advantage of actually blocking the flow of current rather than giving it off as heat.

allan

[commanda]

a standard 120 volt dimmer switch

No. These operate on AC. A 12 volt battery is DC.

What you want is a resistor. You want to drop the voltage to the motor by a couple of volts. As a guess, 12 volts and 5 watts gives 5/12 amps, or 0.4 amps. So a 1 ohm resistor will drop 0.4 volts. A 2 ohm resistor will drop 0.8 volts, and dissipate 0.32 watts. If you were to get, say, half a dozen 2.2 ohm half watt resistors, you can experiment putting them in series until you get the pump running at the wanted speed. 2 of these resistors in parallel will give 1.1 ohms.

Amanda

[Vernon]

The 120V dimmer switch will not work as it requires AC both to commutate the SCR and to provide the basic means of control ... which is to trigger that SCR at a delayed point in the sine wave to control power.

A resistor is crude in that it wastes the power produced by that expensive solar cell. A step down switching regulator is the optimum method. I would try the unit on 5VDC and if that produces the desired flow you can get an off the shelf 12V to 5V DC to DC converter to run the pump ... voltage conversion efficiency is around 90%. If that does not work go to a MOSFET and PWM control...

[hiker]

try a 12v tail light -- just hook it in series with the power line,,,,,

[georgeodjungle]

i had same problem

used a valve on output tube.

adjusts perf.

[Norm]

....or recirculate part of it with a couple of Y

connections and a valve....

               ( :>) Norm.

[Vernon]

If it is a centrifugal pump the valve will also reduce power consumption .. if you are dealing with a positive displacement pump the valve will increase pressure and drag on the motor. A PD pump needs a valve that will simply dump pressure under the surface of the pond if you are going to throttle the fountain.

[Bryan1]

A recent copy of the Siliconchip mag has an easy circuit to control a solar powered water fountain. It uses a 8 pin picaxe chip and a few other components. It also has the source code. The circuit works on the pwn principle with low voltage cutout and a few other features. I must admit for an 8 pin chip the programming is easy as and it's heaps cheaper than a basic stamp. There are a heap of projects out there for the picaxe and I reckon it could solve quite a few issues if ppl start using them.

Just a Thought Bryan

[whatsnext]

Or, you could just increase the diameter of the outlet pipe. This would slow the outlets flow and make it easier to control.

John..........