Hardware Reference
In-Depth Information
4.
Apply +3.3 V one at a time to the driver inputs 1B through 4B
(IN1 through IN4 on the PCB) with a wire, which should cause
the corresponding LED to light. (These driver inputs will also
accept +5 V for testing, if that is what you have available.) If
you breadboarded the circuit, consider adding LEDs to each
driver output.
5.
Measure the voltage at each unconnected driver
input
1B
through 4B (IN1 through IN4). Each should measure 0 V (or
very nearly). If you measure anything higher, you have either a
wiring error or a bad driver chip. Don't use a defective driver.
If this procedure tests out OK, the next step is to wire up the motor (with PCB still
unconnected from the Pi):
1.
Put some kind of pointer on the motor shaft (like a pointer
knob) and wire up the motor to the PCB driver outputs.
2.
Make sure that the COM pin of the driver chip is connected
to the
+
power connection used for the motor (+12 V in my
case). This is important for bleeding off the inductive kick that
occurs when the motor winding is turned off.
3.
Apply power to the PCB and check for smoke. No smoke or
crackling sounds means you can proceed to the next step.
4.
With the PCB power applied, you should be able to drive
each motor winding with +3.3 V applied to individual inputs,
as before. If the motor is wired up correctly, it should twitch.
If the twitch is not visible, put your hand on the shaft. You
should feel it when the winding activates.
The next step is to make sure you wired the windings for the correct sequence.
When applying step 4 of the preceding procedure to each winding's driver input, the
motor should take one step clockwise. Watch for double steps, or twitches in the reverse
direction. As you strobe inputs 1B, 2B, 3B, and 4B (IN1 through IN4) in sequence, the
motor should step in an orderly clockwise direction. Reversing that activation sequence
should cause the motor to step counterclockwise. Keep your nose alert for smoke or
funny smells. Then follow these steps:
1.
Measure the inputs of the drivers 1B through 4B one last
time, while the motor is connected and all motor voltages
are present. Each input should measure near 0 V (due to its
internal pull-down resistances).
2.
Now power everything off.
