How to add reversible dc motor to cheap rc car?

I have a cheap Rc toy car that I was going to hiack the turbo pin to get another channel.
I want to make it into a tow truck and use this extra channel to operate the winch.
BUT I have to be able to reverse it. Giving up and down for the winch.
Can it be done?

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This is the most efficient circuit I have of this.

Apply power to pin A and the winch lets the cable out closing the normally closed switch.

Stop power to pin A and the winch cable retracts until it trips the normally closed switch.

Reversible Drive 12.png
HamishM15 (author)  Josehf Murchison10 months ago

Sorry just had a better look at the other Instructable. Can you just clarify how it will operate the winch please. Thankyou

Like in step 6 of the Instructable the motor is always on. In the video you see me push a button on the circuit board and the motor torques as it reverses. When I let go of the button you can see the motor torque as it goes to forward. The switch on the circuit board is like the turbo pin on your RC.

When the logic output of the turbo pin is 0 the motor on the winch pulls the cable in.

On the cable you have a stop, a bushing on the cable that trips the normally closed switch to open stopping the motor.

When the logic output of the turbo pin is 1 this lets the winch cable out and closes the normally closed switch. It will let the cable out on the winch until the cable reverses it's self on the drum. BAD THING TO DO.

You can stop this by adding a stop switch to the cable when it is out the farthest you want, like in this schematic.

In this schematic the switches are closed unless the cable is out as far as you want or in as far as you want.

Reversible Drive 12.png
HamishM15 (author)  Josehf Murchison10 months ago

Ok I'm kinda following you here.

Are you able to show me physically what you mean by the bushing and stop switches on the cable.

I understand the theory I think just not how to physically do it

For the bushing round split shot like you use for fishing; you would need two, one on the cable between the end of the boom and the hook for the retract stop. The other an inch or two from the end of the cable on the drum.

http://www.bulletweights.com/Products/FishingSinke...

The winch cable assuming you would use braided fishing line passes through a boom: in the boom you put 2 normally closed micro switches.

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On the boom just in front of the winch drum you put one normally closed micro switch with an eyelet on the lever.

Position the switch so that when enough cable feeds out the split shot moves the lever to the open position on the switch stopping the motor.

Do the same at the end of the boom only position the switch so that the split shot moves the lever on the normally closed micro switch to open when the cable is retracted to the point you want it to stop.

HamishM15 (author)  Josehf Murchison10 months ago

Awesome, thanks for your help. Complicated little build but think I've got it.

So just to confirm, this circuit needs constant power 5v (6v ok?) can get directly from the battery, then from "A" being the turbo pin on the chip.

Correct?

Could I use a servo instead of this circuit? With the signal wire coming from "A"?

I was thinking of a retractable landing gear servo from an rc plane as that has already got end points in it. I would just need to know how to trigger it. Wondering if a push button would do it. Push once to go up to its limit, again to go down to its limit.

Thoughts?

That circuit will work from 5 to 12 volts and 650 mW.

If you use a servo you don't need that circuit but you will be limited in winch cable length since most servo's only rotate 90 degrees.

HamishM15 (author)  Josehf Murchison10 months ago

Just had a go at doing a servo (gotta wait for electronics store to open on monday) with no luck.

I put + and - wires to the + and - battery terminals and the signal wire to the turbo pin on the rx chip. Obviously not that simple.

Idea came from this instuctable: https://www.instructables.com/id/Hack-an-RC-cars-unused-5th-channel/step2/About-driving-DC-motors/

After finally being able to download the datasheet on the IC from that Instructable it is made to run a bridge circuit like the one in circuit c of this Instructable where pib B and C are forward and reverse or left and right.

https://www.instructables.com/id/Arduino-Full-Brid...

That is drive and servo.

The turbo pin powers a PMW (pulse width modulator), added power to the wheels.

It is a single logic of 0 or 1 but it has a RC code of turbo and forward or turbo and reverse. So you can only use the pin if you are moving.

HamishM15 (author)  Josehf Murchison10 months ago

Well oops, something touched something it shouldn't have and some of the magic smoke escaped.

Will just rip the guts outta it and put new esc, rx, servos etc in it.

Thanks for your time, effort and patience

Your Welcome

HamishM15 (author)  Josehf Murchison10 months ago

Great thanks, I'll have a crack at building your circuit as it definitely seems to have more adjustment etc.

Once again, thanks for lending your expertise and the prompt replies. Don't go far tho, pretty good chance I'm gunna get stuck somewhere lol

HamishM15 (author)  Josehf Murchison10 months ago
Thanks so much!
However this does not make too much sense to me. I don't really "get" circuit diagrams but am able to put them together once I see the actual components and how they go together.

Are you able to dumb down your diagram at all?

What kind of switch do I need on the transmitter, 2 point, 3 point or push and hold type?

What is "A" on your diagram?

Lastly, can you clarify how this would operate the winch. ie will you push button and it goes to a limit one way then push again and it goes to limit other way?

Thanks for your time

Yes

Use a stop switch and a single transistor inverter driver for a full bridge circuit. (H bridge)

Step 5 of this Instructable:

https://www.instructables.com/id/Arduino-Full-Brid...

You just need the stop switch on the circuit to turn off the return when the winch has drawn the tow cable in fully.

+1

Good and unique design Josehf.

I still like the old school name full bridge or half bridge over H bridge.