Parallax HB-25 Motor Controllers and Braking
October 16, 2012
A friend have found this thread in the parallax forum that has a solution for the not-braking or free spinning of the wheels and I intend to proceed with constructing the "option 1" or in short to short the 2 leads of the motor.
I intend to connect 2 relays (one for each motor) like this: http://letsmakerobots.com/node/528#comment-15665 and http://letsmakerobots.com/node/23424#comment-56001
My question is as to what specs must the relay have, the transistor that will drive it and the diode in parallel with the transistor must be.
P.S.: you can see a small preview of the robot here: http://www.youtube.com/watch?v=CrQDC0QnKMM
P.S.2: it's this robot after a change in chassis and an arm addition: http://letsmakerobots.com/node/33553
-- Update 2012-10-16 14:00 --
The motors are 4 and they are connected 2 per controller (in parallel).
-- Update 2012-10-20 10:37 --
Sorry for the long time it took me to respond.
I was thinking of two options:
- The one uses one relay for 2 motors and
- the other uses separate contacts per motor. (I prefer this one better - the motors could be even slightly different)
Image for option 1:
Image for option 2:
From OddBot I know that the relays must be rated to handle the stall current of the motor which is 1.5A so:
for option 1 I should get a relay rated at least for 4A and
for option 2 I should get a relay rated at least for 2A.
But what about the diode, transistor and resistor?
P.S.: this circuit is going to be replicated twice (the robot is using 2 HB25s) and the transistor will be used to trigger both relays.
-- Update 2012-10-29 12:49 --
Just a small update in the diagrams with part numbers I am thinking of using.