Pololu Simple - Manual (Page 48)

The Error min. and Error max. parameters should be set so that the input channel’s Raw Value is always within that
range whenever the input is operating properly. One way to do this is to move your input to the minimum position, and
set Error min. to be 10–200 counts lower than the current channel value. Similarly, move your input to its maximum
position, and set Error max. to be 10–200 counts higher than the current channel value.
The Minimum and Maximum parameters should be as far apart as possible to maximize the accuracy of your speed
control, but they should still be close enough that you can reliably reach scaled values of ±3200 (±100 %). One way to
do this is to move your input to its minimum position, and set Minimum to be 10–200 counts higher than the current
channel value. Similarly, move your input to its maximum position, and set Error max. to be 10–200 counts lower
than the current channel value.
The Neutral minimum and Neutral maximum parameters should be as close as possible to maximize the accuracy
of your speed control, but they should still be far enough from eachother so that you can reliably reach a scaled value
of 0 when you put your input in the neutral position (e.g. release your finger from the joystick). Some joysticks can
settle at different positions depending on where you release the from, so you should experiment with releasing your
joystick from different positions and see what Raw Values you get (you can see them using “Current channel value”
label or in the Status tab). Then set Neutral minimum and Neutral maximum so that their range includes all of the
values you saw, and has a reasonable margin. This guarantees that you will not waste any power driving your motor
when your stick is in the neutral position.
If you want to restrict the scaled value of the channel to always be negative or always be positive,
you can set the Minimum equal Neutral Minimum or you can set Maximum equal to Neutral
Maximum. This could be useful for one-directional control of a motor but typical applications will
not need this.
5.1.1. Configuring a Limit or Kill Switch
Limit switches and kill switches help protect your motor controller from performing unwanted actions. For example,
analog limit switches could be configured to prevent your actuator from moving out of its valid range. An RC kill
switch could be configured to conveniently immobilize an autonomous robot from a distance using an RC Transmitter
and Receiver.
To configure your Simple Motor Controller to use a limit or kill switch, follow these steps:
1. Decide what channel you are going to connect your limit switch to, and connect it to that channel as described
in
Section 4.4 .
2. If you are using an Analog channel for your limit switch and you decide to use the internal pull-up instead
of supplying an external one, check the “Enable pull-up resistor” box for that channel in the Input Settings tab.
3. If you have chosen a wiring configuration that make it impossible for the controller to detect when your
switch is disconnected, check “Ignore pot disconnect” box in the Advanced Settings. Disconnect detection works
by toggling power to the analog power pins (+) and making sure that this toggling has an effect on the voltage
on the sigal pin (A1 or A2). If you have wired your switch such that the analog power pin is not connected to the
signal pin, you will need to do this.
4. Select the desired Alternate Use for the limit switch channel. This determines whether it will be a Forward
Limit Switch, Reverse Limit Switch, or Kill Switch. See
Section 5.1 for details about the Alternate Use.
5. Click “Apply Settings”.
6. Look at the current channel value label in the Input Settings tab. Press or activate your switch and make sure
that the channel value changes significantly. If the value does not change, then you should double check your
connections and settings and try again.
Pololu Simple Motor Controller User's Guide © 2001–2014 Pololu Corporation
5. Configuring Your Motor Controller Page 48 of 101