Robin Davis

Noise on a2d / PWM BDC motor drive

Discussion created by Robin Davis on Mar 7, 2007
Latest reply on Mar 7, 2007 by Robin Davis
Hi to all.
A mc9s12c32 micro is used in this design. A brushed 24V dc motor is bieng driven
via a H-bridge , using 4 of the pwm Channels.
Basically the h-bridge drive is inducing noise in the a2d signals whenever there is a
transition , high to low or visa versa. At the moment I am filtering out noise in software.
Is there any way I can trigger the a2d convertor when the pwm "waveform" is in the middle
of its cycle , ie where there is no switching noise. If I look at a pwm "Bean" it shows a
pin can be used to externally trigger the a2d , but this pin is being used for something else.
I'm looking for some sort of internal trigger / software option.
Hope I'm not being to vague!!