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pololu motor controller

BadgerBadger Posts: 184
edited 2008-10-10 04:47 in General Discussion
Hello


Does any one out there own a Plolou Dual Serial Motor Controller ... if so i have a noobie question. On page 3 it talks about hooking up the reset pin on the motor controller to the microcontroller. It says you should use a pull-down resistor on the reset line so that if our main controller gets reset the motors do not keep running.

what is a pull-down resistor (definition or what ever) what is a good size and why would it be needed. I know i could google this but tonight i am laid up pretty good and very medicated so please some help would appreciated

Badger the High

Comments

  • TimmooreTimmoore Posts: 1,031
    edited 2008-10-10 02:22
    I have used them. I used a 10K resistor between the reset pin and gnd (pull down to gnd). The reason is that before your software starts up and controls the reset pin, the value of the pin could be floating or high, in this case the motor controller is not reset and trying to do something.
    To be safe if you pull the reset low with a resistor, the motor controller is held in reset until your microcontroller takes control of the motor controller pins so making sure the motor controller doesn't do something you dont want.
  • BadgerBadger Posts: 184
    edited 2008-10-10 02:27
    timmore

    thank you now i understand.. sorry for not looking that up but as i said i am laid up tonight i slipped and almost fell tonight at school and with my arthritis problem it hurt pretty so i am home and laying down and drugged lol

    thanks again


    Badger
  • TimmooreTimmoore Posts: 1,031
    edited 2008-10-10 04:09
    Couple of comments about the controller, somewhere in the spec there is a note about not sending another command within 20ms of the last command - you need to obey this, I have seen funny results if you dont.
    Also if you are running more than 1 controller on the same serial port you will probably see problems of controllers resetting their motor address if you shutdown while commands are being sent to the controller. It took me a while to track down this "feature"
  • BadgerBadger Posts: 184
    edited 2008-10-10 04:17
    Timmore

    do you know if i can run the power to the motors from the boe.. or did no no understand. remember there are 2 motors and only one controller. the controller has it own power source connections but just wondering if i just hook it to the power connections to the boe

    Badger
  • TimmooreTimmoore Posts: 1,031
    edited 2008-10-10 04:47
    I haven't tried a boe so I am not sure, but looking at the boe information it looks like it runs from a 6v battery (4x1.5V). If so I have done similar - from a 7.2V nicad. The motor controller motor voltage I took directly from the battery, i.e. I took the battery power to 2 places the voltage in of the microcontroller and the motor voltage in of the motor controller. I wouldn't try to connect to any of the regulated voltaged on the boe - they probably can't supply enough power for the motors.
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