Motors and Servos.

Using Arduino Motors, Mechanics, Power and CNC
1

Hey,

I have an RC car with a servo powering the front wheels and the a motor running the back.

The h-bridge on the RC cars board has fried which leaves me with no control of the rear motor, in fact I can't power it at all unless I wire a battery directly to it to test it.

This leaves me having to replace the board with a motor controller. However I don't want to break anything or invest wrongly.

Therefore I want to ask what module do you suggest for powering both a 12v motor and a servo?

And is there a difference in how they need to be wired and controlled? Thanks!

2

Where does the Arduino fit in the car?

Seriously, there is not enough information to provide meaningful suggestions. We would need to have a datasheet for the motor to even start and it may be impossible to get that level of detail.

Servos are usually not 12v. 5v or 7.2v is more common. Servos usually run from 2S or 3S batteries. How was the servo powered before? How does breaking the back H bridge affect that supply?

3

You can purchase electronic speed controllers for cars from HobbyKing or some other supplier.

You want to make sure you get the right kind.

If you provide a link to the car you're using, we could probably help you select an appropriate ESC.

I second MoganS' question about purpose of the Arduino. If you just want a RC car, you don't need an Arduino.

Depending on the electronics of your car, you might need to replace the radio system.

4

MorganS:
Where does the Arduino fit in the car?

Seriously, there is not enough information to provide meaningful suggestions. We would need to have a datasheet for the motor to even start and it may be impossible to get that level of detail.

Servos are usually not 12v. 5v or 7.2v is more common. Servos usually run from 2S or 3S batteries. How was the servo powered before? How does breaking the back H bridge affect that supply?

The Arduino is going to fit where the old board used to be, the plan was to remove the chip and take control of the old board and work from there, although the h-bridge which controls the forward and backwards of the motor doesn't work.

The servo is a 9.6v servo I think.

DuaneDegn:
You can purchase electronic speed controllers for cars from HobbyKing or some other supplier.

You want to make sure you get the right kind.

If you provide a link to the car you're using, we could probably help you select an appropriate ESC.

I second MoganS' question about purpose of the Arduino. If you just want a RC car, you don't need an Arduino.

Depending on the electronics of your car, you might need to replace the radio system.

Hey,

I am using a Tyco Street Beast from around 2004ish.

http://www.ebay.co.uk/itm/Tyco-RC-Street-Beast-Ford-F-150-/141823137991?hash=item21055158c7:g:8~UAAOSwNgxWEVv0

This is the best information I can find for it.

The Arduino will be used to control the car entirely, and make it autonomous, therefore I'm likely to add things like GPS, or collision detection at a later date. Therefore I need to use as little of the Arduino pins as possible.

Also, the old board is completely toast. I had the car in storage from when I was kid, and it seems to no longer work since then, only the servo responds from the chip. I would like to replace it anyway, as I can always re-use the board for other projects.

Also, the Arduino is an Arduino Nano as I originally intended to place the Arduino under the original board, so Motor shields may be out of the question? I just need a H-Bridge really to drive the one main motor backwards and forwards. The servo already has a h-bridge built in I believe although haven't checked, I'm mainly assuming because servos I've repaired in the past have had them built in although they are newer.

Thanks.

5

IceCube123:
I am using a Tyco Street Beast from around 2004ish.

Do you know what the battery capacity was? How long could you drive the car on a battery charge (driving near full power). We might be able to figure out how much current your motor requires.

Do you want a "remote control" mode? If so what sort of remote do you want to use?

The HobbyKing ESCs can be controlled from an Arduino so you could either use a hobby ESC or a more conventional h-bridge.

9.6V servos are kind of rare. A picture of your servo might help determine the best way to power/control it. There are a few gear motors which look like servos. These gearmotors in servo's clothing generally only have two wires going into them. If the servo has three wires, it's like a normal one.

6

DuaneDegn:
Do you know what the battery capacity was? How long could you drive the car on a battery charge (driving near full power). We might be able to figure out how much current your motor requires.

Do you want a "remote control" mode? If so what sort of remote do you want to use?

The HobbyKing ESCs can be controlled from an Arduino so you could either use a hobby ESC or a more conventional h-bridge.

9.6V servos are kind of rare. A picture of your servo might help determine the best way to power/control it. There are a few gear motors which look like servos. These gearmotors in servo's clothing generally only have two wires going into them. If the servo has three wires, it's like a normal one.

Hey,

The battery operated at 9.6v (NiCd) also, it doesn't mention the AMP hours on it however. (There is a picture of this below). I'm not entirely sure how long I could drive it at full power it was that long ago since I used it.

As for the remote, I don't see myself adding one, as I use my nitro RC if I ever feel like using one for R/C, and I don't intend on keeping the car for myself.

The servo as you said doesn't seem to be a servo and it doesn't have a h-bridge on it either so it's definitely a DC Motor however is a bit more complex than I expected on closer inspection. There is the power wires, blue and green.

Then there are 4 other wires, which centre the wheels, full left, full right, and what I assume to be a ground wire as it has no function when power is fed into it. When you apply power to the wires which control the wheel position it will move a circle spindle on a circuit board to tell the car the position of the wheels. (images below)

I assume this means I do need 2 h-bridges, and if this is the case what do you recommend? as I want to use as little pins as possible for expandability on the Arduino and to make the car more complex. Obviously without causing harm to the Arduino. I know I need one which allows me to send more than 5v to the motors as well, and will it be safe to hook up the position pins to the Arduino itself?

Thanks for your help :).







Sorry if some of the images are unclear, I did this with little time. If clearer or more images are needed of anything else let me know.

Thanks

7

That's not a servo. It's more like a car windscreen wiper motor that has a 'park' function. See if you can work out the circuit it's using. It is an interesting exercise. I suggest you replace it with a real servo, but for an autonomous car, maybe it will be good to keep it. I would imagine that two Arduino pins and two transistors can control it.

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I was thinking a cheap L298N for the steering motor. I think the four wires can be used as some sort of feedback but probably just for the endstops.

I think I'd use an ESC intended for RC cars for the main motor. An ESC can be controlled with a single I/O pin. I'll let you guess as what sort of current you'll need. I'd suggest getting at least a 20A ESC.

If you decide to power it from a LiPo, I'd think you'd be okay with a 3S pack. A 2S would be safer (less likely to burn out the motor) but not as powerful. I think I'd personally go for a 3S pack but I don't mind burning out an occasional motor (though I have yet to do so (as long as servos don't count as "motors")).

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