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PWM values for DC Motor go awry when pin assigned to motor is initialised after Servo pin #1585
Description
I have a Raspberry Pi zero w running the program and a PCA9685 as the controller to run a DC motor and a Servo motor. When the Servo motor is initialised first, followed by the DC motor, the DC motor rotates at twice the RPM it would if it was initialised first. I checked the voltage coming out of the pins 10 and 9 and the difference would double up for the same speed if the DC motor was initialised second.
Here is the code and the circuit diagram(Fritzing) has been attached.
var five = require('johnny-five'),
keypress = require('keypress'),
board, motor, servo,
Raspi = require('raspi-io').RaspiIO;
board = new five.Board({ io: new Raspi() });
board.on('ready', function() {
servo = new five.Servo({
pin: 15,
controller: 'PCA9685',
startAt: 50,
range: [0, 105]
});
motor = new five.Motor({
pins: [10, 9],
controller: 'PCA9685',
invertPWM: true
});
motor.forward(30);
});Here is the code wherein the DC motor works fine, i.e it gives a low RPM at speed 30 as opposed to the previous wherein it was double the RPM for the same speed.
var five = require('johnny-five'),
keypress = require('keypress'),
board, motor, servo,
Raspi = require('raspi-io').RaspiIO;
board = new five.Board({ io: new Raspi() });
board.on('ready', function() {
motor = new five.Motor({
pins: [10, 9],
controller: 'PCA9685',
invertPWM: true
});
servo = new five.Servo({
pin: 15,
controller: 'PCA9685',
startAt: 50,
range: [0, 105]
});
motor.forward(30);
});Fritzing:
Activity
dtex commentedon Jun 14, 2019
Servos operate in a small section of the possible PWM range but a motor will use 100% of the range. The PCA9685 Expander in Johnny-Five configures a single PWM range for the device rather than a PWM range for each pin. It's not a limitation of the PCA9685, but rather a result of a design decision in Johnny-Five.
I think it's possible to change this, but I wouldn't expect it to happen anytime soon (Unless you're interested in taking it on).
You could always hook either the motor or servo up to GPIO on the Pi.
dtex commentedon Jun 18, 2019
I've added a request for this feature to our "Most Wanted" wiki page and referenced back to this issue, so I'm going to close this for now.