Pololu Simple - Manual (Page 43)

full forward (CH1=max) and steering is neutral (CH2=0), left- and right-mixed motors are both driven forward at full
speed and the robot goes forward. When throttle is neutral (CH1=0) and steering is full right (CH2=max), the left
mixing results in motor forward at full speed while right mixing results in motor reverse at full speed, so the robot
turns right.
As demonstrated above, using both analog channels in mixing mode makes it possible to combine two joystick-
controlled Simple Motor Controllers to achieve single-stick (mixed) control of a differential drive robot. The
connection diagram for such a setup would be very similar to the RC-mixing diagram shown in
Section 4.3 .
Limit/Kill Switches
Unused analog channels can also be used as limit or kill switches. When configured as a limit or kill switch, if the
channel value exceeds more than half of its “forward” value, the switch is activated. If you want to use a push-
button switch for this purpose, we recommend using a normally closed (NC) switch connected in one of the two ways
depicted in the diagrams below:
By using a normally closed limit switch, you ensure that if the switch becomes disconnected in some way, the
controller considers the limit/kill switch active and stops the motor. The left wiring diagram is simpler because it
uses an internal pull-up resistor (enabled using the Simple Motor Control Center), but it can only result in one of
two possible states: switch active or switch inactive. The right wiring diagram above is able to take advantage of
the potentiometer disconnection detection feature. Pressing the switch activates it, releasing it deactivates it, and
disconnecting it results in a disconnection error or an activated switch, depending on which parts of the switch are
disconnected.
The above configurations should work with the default analog channel calibration values, but we still recommend
you use the Channel Setup Wizard (click the “Learn…” button in the Simple Motor Control Center) for any analog
channel you configure as a limit or kill switch.
Normally open (NO) switches can also be used as limit/kill switches with this controller, but they are not as safe since
accidental disconnection will lock the switch in an inactive state.
Pololu Simple Motor Controller User's Guide © 2001–2014 Pololu Corporation
4. Connecting Your Motor Controller Page 43 of 101