Motor Noise, Decoupling techniques

Hello All,
I'm building a small vehicle that uses a couple of optical sensor
as navigation. There are two MCUs, both Freescale HC08 family. The
motors are just small 5V DC brush ones that's been driven at 7.0V,
PWMed to 70% (PWM Frequency 800Hz). There are two motors for a
differential drive setup.
I'm measuring a total idle current of 800mA on the motors, the
load current is about 1.2A, and the stall current at 3.5A.
I'm supplying this system with 5x1.5V AA alkline batteries, the
electrical system is regulated using a 5V regulator. The motors are
driven via a H-Bridge.
During the test, the electrical system appears to be functional
without the motor running. When the motor turns on, the electrical
system fails. Noise riding on the ground lines or VCC lines could be
the problem. Sensors start to provide false output. The two MCUs fails
to communicate with each other using the SPI interface.

Therefore I'm wondering what are some of the techniques to
decouple the motors from the electrical system. I'm about to separate
the circuit VCC out from the 5 AA batteries and use a single 9V batt
to supply the electrical power. I'm wondering if this is a standard
technique?
Also, what are some typical PWM periods been used on small DC
vehicles?

Regards,

PQ
.

Relevant Pages

  • Re: Motor Noise, Decoupling techniques
    ... I'm building a small vehicle that uses a couple of optical sensor ... There are two MCUs, both Freescale HC08 family. ... motors are just small 5V DC brush ones that's been driven at 7.0V, ... the electrical system appears to be functional ...
    (comp.arch.embedded)
  • Re: Motor Noise, Decoupling techniques
    ... There are two MCUs, both Freescale HC08 family. ... motors are just small 5V DC brush ones that's been driven at 7.0V, ... I'm supplying this system with 5x1.5V AA alkline batteries, ... the electrical system appears to be functional ...
    (comp.arch.embedded)
  • Re: Motor Noise, Decoupling techniques
    ... Therefore I'm wondering what are some of the techniques to ... decouple the motors from the electrical system. ... an Up Converter/Supercap type combination to emulate the 9V battery. ...
    (comp.arch.embedded)
  • Re: Motor Noise, Decoupling techniques
    ... motors are just small 5V DC brush ones that's been driven at 7.0V, ... I'm supplying this system with 5x1.5V AA alkline batteries, ... the electrical system appears to be functional ... "Applied Control Theory for Embedded Systems" by Tim Wescott ...
    (comp.arch.embedded)