![]() With regards to PWM, the frequency of the pulses relates to how quickly/slowly, we can get the pulse to the output device. Using this technique, we can simulate an analog output using a digital output. Pulse width modulation or pulse duration modulation is a technique where we vary the width of a square pulse to control the power supplied to any connected device. Controlling the speed of a servo motor using Arduino’s PWM output What is Arduino PWM?.Controlling the speed of a DC motor using Arduino’s PWM output.Code for controlling the brightness of an LED and Arduino’s PWM output.Code for controlling the brightness of an LED and Arduino’s PWM output (using a potentiometer).Controlling the Brightness of an LED using a potentiometer.What are the Arduino functions that deal with PWM signals?.What are the PWM output pins on Arduino?.What are the uses of pulse width modulation?.This timer is also used for the PWM on pins 9 and 10, but the library doesn't actually use PWM at all. The servo library actually doesn't use PWM to generate its pulses, it uses one of the timer interrupts on timer1. ![]() You could decrease the PWM frequency to for instance 60 Hz which would give you 17ms pulse spacing which is close enough to 20ms that it might work, but this would lower the resolution of the pulse length to 65us. If you decrease the duty cycle then the pulses would get the proper spacing, but become too short. This doesn't mean anything to the servo, because the pulses happen way to fast. If you set a 50% duty cycle, you'd get a 1ms high pulse followed by a 1ms low pulse. The PWM on an Arduino generates an (approximately) 490 Hz square wave. Doing write(844) would have the same effect as doing write(33), so maybe you could use this to your advantage to get a higher resolution (though I imagine your concerns about it never being "truly neutral" are unfounded because servos are only so accurate). If it's more than 180, it's treated as a value in microseconds (for the pulse length) directly. Servo's write function is actually kind of weird: it treats write(x) differently depending on the magnitude of x: if x is less than 180, it's treated as an angle and 0 is mapped to the servo's min, and 180 to the servo's max. The min value of 33 gets translated to a 844us pulse, whereas your max of 152 becomes a 2111us pulse. These pulses need to be spaced apart somewhat, for instance by 20ms. For a typical hobby servo, a 1ms pulse represents one extreme of the rotation, a 2ms pulse the other, and a 1.5ms pulse represents the middle. A servo is controlled by sending it short pulses of the control pin going high. I can probably fix this by raising the max speed a little until it hits 153, but honestly I'd much rather just convert over to analogWrite() before I start fixing little things like that. The average of 33-152 is 92.5, which isn't an integer, so I can never truly get a neutral value from the pitch, roll, and yaw. ![]() Through a little trial and error, I found that my Servo.h min/max values are 33-152. Some more useful info: my motors have min/max speed settings, so they're never completely off and never at full 5V. What's really going on though? Why is one PWM function working but another isn't? write() works with values 0-180 (someone correct me if I'm wrong), so I just had to tweak the values a little. It worked! Instead of analogWrite's value of 0-255, Servo.h's. write() function, since that also sends out a PWM signal. Getting a little creative, I made use of Servo.h's. To send those PWM signals, I tried using analogWrite(). ![]() I used CleanFlight to configure the Naze board and everything is working great. Yay! To control it, I'm sending PWM signals to a Naze32 flight controller, which powers the four motors (it's a quadcopter). So I just built my first Arduino-powered autonomous drone. ![]()
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