motor control chip consumes too much power?

Go To Last Post
4 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

i have a motor control chip that i am controlling via an avr... when the motor kicks on or changes directions, it briefly consumes too much power, sometimes causing the avr to malfunction.... the motor i'm controlling only requires 5v, so i have the motor controller's supply voltage line hooked to the same 5v voltage controller that the avr is... i am powering the 5v voltage controller with a 16v supply... can anyone give me a hint as to how to stop the spikes?

the motor controller i'm using is this one:
http://www.sparkfun.com/datashee...

when i hooked a 1uf cap to the vcc2 pin on the motor controller, the controller did not function at all.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

motors will consume large amounts of current to get moving. This may result in large transients on your supply, if you don't have adequate filtering.

[edit]
If the driver stopped working when you added the cap, you must have added the cap incorrectly. Sounds to me like you added the cap in series, instead of in parallel to the controller. (cap should be placed between the supply pin, and gnd)

Also as per the datasheet you should have diodes placed across each output and the supply and ground voltages.

The motors supply should be fed directly from its own branch from teh supply, and not across traces that are feeding other components.

To help isolate the spikes form the rest of your circuit, place a (schottky) diode on the branch feeding the logic, followed by a largish cap. The cap will power the electronics when teh motor pulls the supply down.. the diode will prevent the cap from being drained by the motor.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Thanks for the advice.

How should the cap that will feed the electronics be hooked up? Should it be hooked directly from vcc to a branch that feeds vcc to the electronics?

Also, what would you consider a good size cap to use? The electronics i'm using consist of an avr, a 5v adc device, and the motor control chip.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

No, it should be connected between Vcc and ground, as glitch already told you.

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here

No guarantees, but if we don't report problems they won't get much of  a chance to be fixed! Details/discussions at link given just above.

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]