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ESC regulated with mechanical potentiometer?

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ESC regulated with mechanical potentiometer?

Old 06-28-2013, 09:38 PM
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Sixtysixdeuce
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Default ESC regulated with mechanical potentiometer?

So I got my 3 YO daughters a pair of Power Wheels lil wranglers for their birthday. They were on clearance for $50 at wally world (thank goodness, because they're not worth much more). Right off the bat it was clear that one wheel drive wasn't gonna cut it, so using some roll pins, I made them 2WD with ball bearings on the rear live axle. Now that they actually get traction, the anemic nature of the 6V system reared it's ugly head, so I stuffed 6,600 mAh 3S LiPos in them. Well, they sure go now, but the increased voltage coupled with the discharge rate of a LiPo is going to give the kiddos whiplash and trash the gear boxes.

So, I have a couple of 320A brushed ESCs coming, and a couple of 50K ohm potentiometers. My question to the electrical wizards among us is wiring them up; I'm thinking it's normal power in to the ESC from the stock power wheels switch, then power and ground on the red and black wires from the receiver plug, and put the potentiometer between power and the white wire. Does that seem right, or am I going to need more electronics, perhaps even a receiver to make this work?

Also, if this can work without a receiver, would reversing be achieved by switching the polarity of the wires on the receiver plug to the ESC?

I should know this stuff, but I'm more of a mechanical builder, and I don't really play with electric RC. I'm a nitro guy. Just never tinkered with an ESC to see what makes it tick.

Thanks in advance!
Old 06-28-2013, 09:52 PM
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SyCo_VeNoM
 
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Default RE: ESC regulated with mechanical potentiometer?

I'm guessing you want to control the throttle from the ESC using the pot if so use the circuit from this link http://www.helifreak.com/showthread.php?t=275749 (Been meaning to make one of these as I'm more then certain I got the parts just laying around)

As for reversing I would guess if you center the pot and calibrate the ESC for it being centered if you rotate one way it will got forward, and rotate the opposite it will reverse.

just hooking the pot up to the white wire won't do anything as its controlled by PWM (pulse width modulation), and not changing the amplitude of the voltage going into it

BTW the brushed ESC you ordered I HIGHLY doubt could take 3S lipos as most can take only like 8.4 volts to 9.6 max
Old 06-28-2013, 09:59 PM
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Sixtysixdeuce
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Default RE: ESC regulated with mechanical potentiometer?

Thanks! That is most helpful.

BTW the brushed ESC you ordered I HIGHLY doubt could take 3S lipos as most can take only like 8.4 volts to 9.6 max
I couldn't find an input voltage rating on these critters, but they were only $10/ea, so if I smoke one, oh well [8D]

ETA:

I'm kinda rethinking using RC ESC. I found 350W 24 V rated scooter ESC on ebay for $15, and $20 for the thumb style throttle. That'd be easy to wire in, and can definitely handle the power.

I'll just use those two ESCs when I build the girls their next RC cars or something.
Old 06-29-2013, 09:11 AM
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Default RE: ESC regulated with mechanical potentiometer?


ORIGINAL: Sixtysixdeuce

Thanks! That is most helpful.

BTW the brushed ESC you ordered I HIGHLY doubt could take 3S lipos as most can take only like 8.4 volts to 9.6 max
I couldn't find an input voltage rating on these critters, but they were only $10/ea, so if I smoke one, oh well [8D]

ETA:

I'm kinda rethinking using RC ESC. I found 350W 24 V rated scooter ESC on ebay for $15, and $20 for the thumb style throttle. That'd be easy to wire in, and can definitely handle the power.

I'll just use those two ESCs when I build the girls their next RC cars or something.
A scooter ESC probably would be best as honestly I doubt a RC ESC could power a power wheels motor for long as those cheap HK ESC's I've seen one smoke in a mildly geared tamiya on a 27t motor.


I have been tempted to buy a power wheel to make into a giant scale RC car though
Would be interesting to see one with the 1/5th scale BL motors in it
Old 06-29-2013, 09:24 AM
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Sixtysixdeuce
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Default RE: ESC regulated with mechanical potentiometer?

Would be interesting to see one with the 1/5th scale BL motors in it
The stock motors are just cheap 540 cans-I would think even a 1/8 brushless would move them pretty good.

Having played with more than one power wheels, though, I'd say the body is about the only useful part for an RC application. No suspension, and no solid way to really mount stressed parts. I'm planning to build aluminum suspension chassis for these ones, and to make them 4 wheel drive using another gear box assembly, some HF1012 one way bearings and 1/4" drive extensions & universal joints.
Old 06-29-2013, 09:46 AM
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Default RE: ESC regulated with mechanical potentiometer?


ORIGINAL: Sixtysixdeuce

Would be interesting to see one with the 1/5th scale BL motors in it
The stock motors are just cheap 540 cans-I would think even a 1/8 brushless would move them pretty good.

Having played with more than one power wheels, though, I'd say the body is about the only useful part for an RC application. No suspension, and no solid way to really mount stressed parts. I'm planning to build aluminum suspension chassis for these ones, and to make them 4 wheel drive using another gear box assembly, some HF1012 one way bearings and 1/4'' drive extensions & universal joints.
seriously just 540's? Wow they came down I seem to remember from when my sister was little and had one the motor was pretty big. But then again it was probably around 20 years ago so my memory could be a bit off.
Old 06-29-2013, 09:49 AM
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Default RE: ESC regulated with mechanical potentiometer?


ORIGINAL: Sixtysixdeuce

Would be interesting to see one with the 1/5th scale BL motors in it
The stock motors are just cheap 540 cans-I would think even a 1/8 brushless would move them pretty good.

Having played with more than one power wheels, though, I'd say the body is about the only useful part for an RC application. No suspension, and no solid way to really mount stressed parts. I'm planning to build aluminum suspension chassis for these ones, and to make them 4 wheel drive using another gear box assembly, some HF1012 one way bearings and 1/4'' drive extensions & universal joints.
probly is 540 in the smaller wheels. in larger power wheels, its more like a 700. If a titan 775 can be made to fit, that will up the torque a bit.
Old 06-29-2013, 12:56 PM
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Default RE: ESC regulated with mechanical potentiometer?

probly is 540 in the smaller wheels. in larger power wheels, its more like a 700. If a titan 775 can be made to fit, that will up the torque a bit.
Could be, I've never been into anything larger than the standard Barbie jeep 2 seater (barely) size.

Drive unit for the 'lil Wrangler:



The 'lil Wrangler uses only one of these drive units on 6V, but the larger 2-seaters use duals on 12V. The spare unit pictured I bought to do the 4x4 conversion.

Small as they may be, on the 3S LiPo, it was enough to startle my kids. Top speed probably only 5-6 MPH, but with the LiPo discharge, it's right now, especially with a non-differentiated solid rod rear axle and the screws I ran into the wheels to give them traction on dirt. That's why I want to retrofit a variable throttle system.
Old 06-29-2013, 06:32 PM
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Default RE: ESC regulated with mechanical potentiometer?

Go to http://www.modifiedpowerwheels.com/that isTHE website dedicated to just what you are trying to do here, by people who actually do it and know what they are doing. It could save you a lot of headache and $$. They also address the traction issue with most power wheels. Be sure to check out the videos section.

Check out these videos.

8mph Power Wheels

[youtube]http://www.youtube.com/watch?v=7u2AIYyJmh0&list=TLV4hX8aKrxuI[/youtube]

Traction bands

[youtube]http://www.youtube.com/watch?v=AAySJVt6bys&feature=c4-overview&playnext=1&list=TLV4hX8aKrxuI[/youtube]

There are lots more there!!

Cool Project!! Would like to see what you end up with, keep this updated please.

Hope this helps
Old 06-29-2013, 11:45 PM
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Sixtysixdeuce
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Default RE: ESC regulated with mechanical potentiometer?

Go to http://www.modifiedpowerwheels.com/ that is THE website dedicated to just what you are trying to do here
I've checked out that site, just didn't feel like registering and figure there's more knowledge here about RC ESCs, since that was my original plan.

I did actually have the idea of using cut bicycle tires, though I'd have to find 10" tires for their little jeeps. But since the axles are locked and they drive exclusively on dirt/grass out here in Elbert county, I decided that the sheet metal screws as studs along the smooth center rib of just one tire would provide sufficient traction. I was correct, as they nearly do wheelies in the yard with the LiPo batteries. I did only one wheel so that the other could slip when they're turning, since the axle is just a solid rod with no differential.

I will probably outfit them with 10" pneumatic tires down the road once I have variable throttle installed, but will have to do some kind of differential set-up once both tires have high traction, or the vehicles won't turn for poo. In the end, the body tubs will probably be about all that's left of the original vehicle.

I just can't leave anything alone. lol. The chassis tub & hinge pins are the only original parts left on one of my RC10GTs, the other retains only the tub, fuel tank & front suspension. I stuffed a big block in my '78 Aspen, along with a Jeep Dana 44 rear end and many other non-Aspen parts. We'll not even discuss the wacky ideas I have for the garden tractor, except to say more cylinders and not natural aspiration.

I'm not sure if I get more enjoyment out of fabbing totally custom parts, or adapting things that were never meant to fit.
Old 06-30-2013, 12:04 AM
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Default RE: ESC regulated with mechanical potentiometer?

Pluss one on that forum....

I've got a 2 seater jeep looking thing, twitch the twin motor setup.... It's a blast.

I once converted it to 4wd with 4 motors and gearboxes, but was way to hard for the kits to steer. So it's now 2wd...

I found discharge rates don't really matter. mine for example has a auto resetting fues in line with the motor, to protect it from overloading.

Most ride on cars will take 18v with no problems, 3s lipo will be ok but nothing that crazy.
Mine is running 2x 12v led acid batteries from a old starter box, with a switch that changes the wiring from series to parallel.

It's pretty crazy on 24v... to much for my younger boys, but my 8yo daughter loves it.

Ps, u can get "servo testers "from eBay for under $5...

I've dreamed of the same idea u have. Using a brushless combo but on 6s
U could use a existing servo tester connected to the ESC for the throttle.
Then to get it working, physically block the POT switch so it can't go in reverse, ie half it's rang of motion.
Then set up 2 relays and a switch on the motor wires that reverses the polarity.... Then u have reverse again.
Not to get the pedal working with the POT switch.
I thought a rack and pinion setup with a return spring would work a treat. Fit the rack to the pedal and a pinion directly to the POT switch.
Old 06-30-2013, 12:07 AM
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Default RE: ESC regulated with mechanical potentiometer?

He he ive even had dreams about making front and rear 4 link suspension from metal tube and some 49cc quad shocks....

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