H-bridge / toy car voltage & arduino

hi guys.

I'm working on a car for my son. Everything should be controlled via Xbee, but really I'm at the step before.

I'm actually driving two dc motors in both directions via arduino.
using a L293D (which should be enough for the all thing)

this image is preatty close to my circuit, but I'm using also the upper parte of thecircuit


Everything seems to work, but vey slowly.
I explain.
If I cchel if both motor are working, connecting a battery to the wires, bot motors a re spinning very fast.

this doesn't happen thorugh the H-bridge.
I'm not using any capacitors, can this be the problem (and if then, where should I place them?)

oddly enough, the original circuit used for both motors 7.5V, I'm using 9V batteries for each one!!! :o :o :o
Note: I'm criving noth enable pin though analogWrite 255

please help

thanx

The L293D loses 2.5-3.5V at 600mA due to voltage drop across the bipolar driver transistors.

If you're using 3V motors, you should switch to a motor supply of about 6V to compensate for that. You should also check how much current the motors are really using: many people using low-voltage motors have been surprised by the actual measured amount, and an L293D might not be up to the job.

Ran

thanx ran.

yes. you are right.
I need higher voltage to have everything working.
(but I just need 5V on Vcc1 for the chip to work.

I'll answer here how the all thing is doing.

thanks for the quick answer.
dave

What program did you draw this schematic with?