Hi to all! My robot project is based on RC car. I use two hardware PWM outputs of my FEZ Raptor to control ESC (motor) and steering servo, but when i load the ESC (motor) to full power (PWM.duration = 2000, PWM.period = 20000), my steearing servo PWM start to behave wrong (it start to turn righ or left by itself). When i load the ESC (motor) on a half power 50% or 75%, steering servo PWM behaves as expected. Solving the problem i made a separate power supply (FEZ Raptor and ESC are supplied from the different sources) but it didnt solve the problem. I think the problem is in the power load… maybe someone meet the same problem, help me to find a solution please.
I am not sure but I think this maybe related to PWM channels. Changing the frequency on one would effect the other. While your motors use same frequency with different duty cycle, servos use different frequencies (changes the pulse). Check the datasheet to see which PWM channels are independent, or just try a different P socket.
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@ Gus -
Thank you for reply. According to spec Raptor has 4 hardware pwms (three of them on 18 socket, one of them on 16 socket) I use 18 socket (7 pwm pin for steering servo, 8 pwm pin for ESC, common GND for both). But i have to get 5v power supply from ESC (i use the ESC 5v power supply for steering servo), because FEZ Raptor doesnt give me a 5v, it gives only 4,74-4,89v from the 5v pin and i dont know why? Maybe you know why? Steering servo need not less than 5v power to start, if less it doesnt even start. And i am pretty sure this is a problem, when the ESC use a full load, it loads the whole circuit and influence on servo voltage supply.
- Tried another P socket(16) for servo. It didnt solve the problem.