Speed Control Of DC Motor

[shyam4uall]

Guys I want to vary ( or u can say want to decrease) the speed of the motor inside my RC car.The motor used is a DC one(  i think) as its a low priced RC car.

Would it be require to alter the readymade circuits which are built-in receiver?or is it possible to control the speed externally through some other circuits?I wont like to go with the option of using gears so if possible is there some other way out i.e some sort of circuits(PWM,some IC etc.)

If anyone can give the links to those circuits ...i will be very thankful...

[ArcMan]

Let us know what you're trying to accomplish.  Convert the car to an autonomous robot, just add speed control, etc.

[shyam4uall]

Nope..

i have interfaced the transmitter with my PC through parallel port which enables the navigation to be controlled from PC.

I want that the car should move slowly or if possible...i can adjust the speed ?

[ArcMan]

That depends on several things.  Is your transmitter/receiver capable of variable speed commands?  Is it the standard R/C servo PWM type?  If it is, you can connect a standard R/C car variable speed drive to it.

[shyam4uall]

That depends on several things.  Is your transmitter/receiver capable of variable speed commands?  Is it the standard R/C servo PWM type?  If it is, you can connect a standard R/C car variable speed drive to it.

I don't think the motor is a servo one because it (car) moves with a constant(or fixed) speed.The receiver which is there inside the car gets its supply from 6AA size battery (each of 1.5V).So how to modify the circuit using external chips or ICs and where to connect them ?

[ArcMan]

OK.  I think I have a mental picture of the car.  It's the $20 K-Mart one, right?

I know you're doing this for a learning experience, but you may want to invest in a decent R/C car from a hobby shop and start learning from there.  These cars come equipped with a variable speed control system and continuous servo steering.

Or is there a particular reason you have to stay with this car - like a robot contest?

[DaveX10]

you may want to invest in a decent R/C car from a hobby shop....... Or is there a particular reason you have to stay with this car - like a robot contest?

I agree with ArcMan. However.... you could look at (research) using a resistor at the drive motor. Starving the motor of current might slow it enough... and for pennies. Be sure to expell the heat properly. 

[shyam4uall]

thanks to all....i am trying...a process and lets see what happens at the end.And yeah low current is becoming a issue,so working on it.

[SciTech02]

Hobby-grade RC speed controllers should be fairly cheep (RC airplane speed controllers are around $20-$30).  Check your local hobby stores, hobby websites and even eBay.  IMO, this is the easiest method; you could get the motor working and focus on creating the PC control interface.

[Admin]

you could look at (research) using a resistor at the drive motor. Starving the motor of current might slow it enough... and for pennies.

but it wastes battery energy . . .


These hook right up to your receiver to control a motor:
http://servocity.com/html/speed_controls.html
http://www.dimensionengineering.com/ (see motor drivers)

[merrixs]

I'm not sure if this will interest you, but when I want to get my hobby grade radio control truck to to have a slower top speed with the addition of more torque I sometimes modify the motor because it is easier than adding more gear reduction.  A lot of us do this in rock crawling applications.  If you would rewind the motor and add more winds or wire the motor it will have a slower speed with increased torque and runtime.  This will not let you vary the speed on the fly, but it will make it slower with out wasting energy.  Hope this helps.

[offencerobotics]

well if your using the parallel port to control it just pulse the motor on and off to the speed you want

[WhomBom]

You could try and take one cell out of your car's battery pack. This will result in a lower voltage from your battery pack, decreasing the power your motor delivers (at full throttle, but i gather from your description that's fixed). Provided your electronics still work at that lower voltage it should work..  If they don't you could try a small separate battery pack (or 9V block even?) for your electronics.