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Electronics => Electronics => Topic started by: iaaly on May 24, 2010, 03:11:27 PM

Title: L298 problem
Post by: iaaly on May 24, 2010, 03:11:27 PM

Hello Everyone,

I am facing a problem in my project, I wish to control an RC toy car with micro-controller, so I have bought a DC motor Driver L298,
Everything is OK, I can manage to control 2 dc motor( PWM speed control and direction changes all ok) , but when the car contact the ground, the motor stops,
I have measured the current with a multimeter, when contact with floor, the motor need about 1.3 A, but the driver only gives 0.36A maximum, so that the motors stops

This is the link of my schematic (http://yfrog.com/0pl298problem2p)

What should I do ??
Please help,
Best Regards

Title: Re: L298 problem
Post by: SmAsH on May 24, 2010, 03:31:01 PM

You probably need to buy a higher output motor driver...

Title: Re: L298 problem
Post by: iaaly on May 24, 2010, 03:41:37 PM

like what ??

Title: Re: L298 problem
Post by: z.s.tar.gz on May 24, 2010, 04:31:46 PM

From what I saw it seems as if you should be getting plenty of current. (Datasheet says 3A max per channel)
This signifies either a problem with your pwm signal, your wiring, or your power supply. I'd check wiring first.

Title: Re: L298 problem
Post by: Cristi_Neagu on May 24, 2010, 04:42:05 PM

If it's an RC car, it's most likely the power supply or batteries. It takes a pretty beefy power supply to provide 1.3A of power. That's almost 3 cell phone chargers and those are switching power supplies.

Also, i noticed your design doesn't have flyback diodes... That could fry the L298.

Title: Re: L298 problem
Post by: Soeren on May 24, 2010, 04:57:48 PM

Hi,

Quote from: iaaly on May 24, 2010, 03:11:27 PM

What should I do ??

Apart for the flyback diodes that you need to protect the IC, your real problem here is that your sense resistors (R1 and R2) are way too high. Reduce them to 0.5 Ohm each and your car will run.

For a quick test, if you haven't got such low value resistors, just use a short circuit to replace R1 and R1, but only for a short test to verify that it works!
Don't do this until you have the flybacks in place, or it may kill the chip.

Title: Re: L298 problem
Post by: iaaly on May 26, 2010, 02:53:04 AM

Quote from: Soeren on May 24, 2010, 04:57:48 PM

Apart for the flyback diodes that you need to protect the IC, your real problem here is that your sense resistors (R1 and R2) are way too high. Reduce them to 0.5 Ohm each and your car will run.

Soeren, I don't know how to thank you !! you are right 100 % ..
I have added the flyback diodes and replace the resistors form 10 to 0.5 Ohms, and It's working well ...
Thank you very much  :)