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Can I make a 15W+ 1-5Ohm resistor? Answered

I'm making a yard sprayer with a 12V, 5amp pump.  It works great, but I'd like to add in a 2nd, slower speed setting for situations where I want less fluid going through the sprayer.  It needs to a be a simple fast/slow switch, not a variable resistor, since I need the flow rate to be repeatable and consistent.  Ideally, I'd like to make about a 2-ohm resistor, that would need to be able to handle about 15W.  Unfortunately, no local shops have anything like that, and I don't want to wait for an on-line order to get shipped.

Is there any way to make a DIY resistor to roughly achieve these characteristics?  (Like I said, the important part is that it will be a consistent resistance value, not a specific resistance value, and not burn up with 2-4 amps going through it..)

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steveastrouk
steveastrouk

8 years ago

Don't use resistors to do it. An adjustable voltage regulator is much better for the motor.

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lemonie
lemonie

Reply 8 years ago

The voltage-regulator would waste-heat; why not PWM?

L

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steveastrouk
steveastrouk

Reply 8 years ago

Overly complex for thesize of load really. PWM is a good idea, but you need the electronics knowledge to put one together.

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lemonie
lemonie

Reply 8 years ago

Yes I can understand that, thanks.

L

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LesB
LesB

8 years ago

I agree with steveastrouk for a permanent solution. However it looks like you're in a hurry for this one.
As a quick >>temporary<< solution you can experiement with different wattages of 120V incandescent light bulbs. Start with a 100W if you have one.
I regard this as just a temporary solution. Motors lose torque when controlled by a series resistor.

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steveastrouk
steveastrouk

Reply 8 years ago

They become much more sensitive to the load too.