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[on:]

Hello All,

I'm trying to control a RC Car composed by one motor and one servo. The problem is that the RC Car is quite old and I don't have much information bout the components. The RC car, was poweres by a 7V-1200mAH Battery, but this battery doesn't work anymore. I isolate the motod and the servo from the central chip in order to make my own circuit with arduino.

I try to plug a 9V Cell. I got an ohmeter and the motor have 55ohms of resistance.

How can I know the maH that the Cell have? How can I make this motor run?


PS: The motor only have 2 wires. One red and another blue. I tink that its a positive-ground only powered motor.

Thanks in advance!

[Reply #1 on:]

"mAh" is not a rating for a motor.
A 9V battery is probably not going to provide enough current to drive a motor.

Can you post photographs?

[Reply #2 on:]

55Ω seems much too high for an RC motor.  Somewhere in the range from 0.5 to 4 ohms  might be more like the correct value
Your best bet with respect to batteries would be to get a 6-cell (7.2v) nicad type as used in the original build
You need to check your motor out first to confirm it is not damaged.  With the motor disconnected from any other devices simply connect the battery to the motor terminals.  The motor should run which confirms it's OK.  If it does not run then your first task is to either repair or replace.
Jack

[Reply #3 on:]

Tomorrow  I will post some photos of the motor.

The battery is broken and the charger missed, so , I don't think that the motor runs if I connect the wires to the battery... I will search for a cheap battery to buy and I will post my feedback.

Thanks!

[Reply #4 on:]

DC motors like this are rugged and not picky. They will spin if you hook them up to a source of voltage/current, and they will spin faster the higher the voltage. Basically the only limit to how much voltage you can apply is that the motor will start to get too hot and either burn up or demagnetize. So as long as the motor is not getting very hot, you are fine. Use whatever battery you want.

[Reply #5 on:]

...but don't use a battery incapable of providing sufficient current, like the sort of 9 volt battery you'd normally find in a smoke alarm.

[Reply #6 on:]

Even those little 9V will usually spin a DC motor...even a big one like a drill motor...if there is no load.

[Reply #7 on:]

Hi,

I often break in my RC Race car motors by running them from a single 1.5v D cell. If you can get the motor out of the car, it should run from one of these cells. If you can't get it out of the car, you should still be able to get it to run from one of these cells unless the gears are binding in which case you will have to take the car apart and fix whatever mechanical issues it has.

In cars that are left for a long time, the grease in the gearbox can turn hard in which case you will need to clean this out before getting the car to run.

As others have said, you will not get the car to run well on domestic batteries, ideally you want Nicad, Nimh or the most recent technology LIPO batteries. All of these require an investment in a new battery and charger so be sure the mechanics work well before investing in these.

Duane B

http://rcarduino.blogspot.com/