grounding a plastic chassie

[Koldham]

i am wanting to wire a stereo pot to the power wire of one of the motors that drive my machine. its a cheap rc car and the motors are either on or off, no speed control. a pot has 3 pins. one for input, one for output, and one for ground. where do i hook the ground to?

[JohnRobHolmes]

How big is the motor, and how big is the POT? Without knowing the details I can say that it probably will just end with the POT on fire.

Input is positive to battery. Ground is negative to battery and motor. Output is positive to motor. If you are pulling 50w at half POT setting (half throttle), the POT will be dissipating 50w of heat as well. I don't know of any POTs that will take more than a few watts of heat before the traces blow.

[Duuuuuuuude]

Expect this:

[Koldham]

well im sorta turning a tank into a missippi paddle wheel boat so i could use the water to disssipate heat, and there isnt nearly that much energy going to the motor, its tiny and i can stop the motor rotation with my toung.

so i would hook it to the batterys negative terminal?

[Duuuuuuuude]

Originally Posted by Koldham

i could use the water to disssipate heat

You're going to water cool the stereo pot?

Expect this:




Just buy a $15 speed control and be done with it.

[JohnRobHolmes]

Indeed. A speed controller is the normal fare on a boat for a reason. If POTS were better for anything except gain control, trims, and positional feedback they would be used for RC boat power already.


But if you just want some fun, give it a shot and play with some electrical fire. At your own risk, you have been warned.

[Charlie-III]

You "could" use a pot twisted by a servo as a cheap speed control. I would wire from the battery pack to the motor, lets say the "+" side.
Then wire from the battery pack "-" to an outer pin on the pot, and the center pin to the motor "-".
The servo can then be used to twist the knob on the pot to vary the speed. Whether you do a gear drive or use a servo arm.

[JohnRobHolmes]

Originally Posted by Charlie-III

You "could" use a pot twisted by a servo as a cheap speed control. I would wire from the battery pack to the motor, lets say the "+" side.
Then wire from the battery pack "-" to an outer pin on the pot, and the center pin to the motor "-".
The servo can then be used to twist the knob on the pot to vary the speed. Whether you do a gear drive or use a servo arm.

I like your wiring better than mine, I'm taking notes now



Rewiring classic mopeds is a strange art. Everybody has their own way of doing it. Just like skinning a cat...

[Duuuuuuuude]

Originally Posted by Charlie-III

You "could" use a pot twisted by a servo as a cheap speed control. I would wire from the battery pack to the motor, lets say the "+" side.
Then wire from the battery pack "-" to an outer pin on the pot, and the center pin to the motor "-".
The servo can then be used to twist the knob on the pot to vary the speed. Whether you do a gear drive or use a servo arm.

He would still need a big, heavy pot to handle the load, even one as small as he claims it to be.

Still cheaper and easier to get a cheapo esc instead of cobbling together a msc.

[Greatscott]

I think it really depends on what part of the stereo the pot was on. If it was on the output side of the amp, you might be ok, if was on the input side, you'll likely fry it.

Cooling isn't so much the issue as the load capacity of the pot itself. Assuming a modest load of 1 amp, that is still way far beyond the load capacity of most of the pots on your garden variety stereo.

Do yourself a favor, go to your local Radio Shack and get a POT rated for at least 3 amps, and not one designed to only attenuate signal, I think it will cost you a buck or so.

[Charlie-III]

Originally Posted by JohnRobHolmes

I like your wiring better than mine, I'm taking notes now



Rewiring classic mopeds is a strange art. Everybody has their own way of doing it. Just like skinning a cat...

Ex facilities guy and current field tech/hobbiest, I've learned ways to make due with what I have.

(taking notes, I'll take that as a compliment!)

[Charlie-III]

Originally Posted by Duuuuuuuude

He would still need a big, heavy pot to handle the load, even one as small as he claims it to be.

Still cheaper and easier to get a cheapo esc instead of cobbling together a msc.

I totally agree, he would likely really need a wirewound pot, they can be big & heavy, but hey, just trying to help him out.
He would be better served with a used "almost anything" ESC though.

[Koldham]

so i got an electronic measuring tool and the motor under no load pulls .4 amps. at full load it pulls 1.6 amps. at normal service it pulls about .7 amps. i think i can do it with a patch cable pot . nothing lost is nothing gained!