I'm not using PWM yet. The motors get all +18V when on. At 9V the robot did not go so fast. Now I got two 9V batteries in series. Then the speed should be decreased to about 70%.
When the robot has to turn, I cut of one motor for a moment, low on both inputs on the L293 for that motor. This implies that the motor breaks. By lowering the enable pin the motor should go to a free-running stop.
The noise from the motors, could that be coursed by to much voltage? They are loader-motors from a video-machine. I have been seeking datasheets on the Internet for these motors. As far as I can see, they are normally operated by +12V.

 

What does it sound like?

Some motors squeal when they are run too fast as the bearings are working beyond their limits, perhapps you could use PWM to slow it down to a safe speed.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez

 

They don't go to fast. It's when they are blocked the noise comes.

Maybe I should add that L293 did not heat up.

 

I WANT FULL CKT DIAGRAM OF VOLTAGE DOUBLER WITH ALL ITS WORKING
I ALSO NEED ITS COMPONENTS SPECIFICATION WILL ANYBODY HELP ME
MY ID := PSB2PSB@YAHOO.COM

 

psb2psb,

Google: 555 voltage doubler
13200 answers to your query.

Ken

__________________
"To invent, you need a good imagination and a pile of junk."
Thomas A. Edison (1847 - 1931)

 

instead of using the voltage doubler with 555, where you don't get regulation of output, better try using MC34063 with few components. the inductor caould be wonld by hand or ready purchased like 10uH
the datasheet can be freely downloaded from www.alldatasheet.com

the circuit behaves well and output is regulated. the pcb layouts for various configutations are provided in datasheet. though old IC, it is really good. you will get it at any components supply houses as you are in US.

__________________
Regards,
Sarma.