I'm trying to understand the difference between two 12V PWM circuits I've build and tried.
The PWM signal is intended to control the speed of a motor. Only not in the way you would expect. The motor has its own circuitry and accepts the PWM signal as a speed control. So its not driving the motor directly.
To make this work I've tried two PWM control circuits:
I got a PIC to generate a PWM signal. I tried both the build-in ECCP module and software PWM. I used the following circuit to convert the PWM from 5V to 12V.
Although this produces a very nice 12V signal the motor doesn't react to it all.
So I tried an old fashion NE555 in astable mode to generate the PWM.
Schematic from DPRG
This circuit also puts out a nice 12V PWM signal with the same frequency and duty cycle as the PIC circuit. But this signal actually does have effect on the motor.
So my question is: What is the difference between the PWM signals generated by these two circuits/devices? By knowing this, I hope I can change the PIC circuit in such a way that motor reacts to it aswell .
Since I rather control the motor with the PIC, as this will make for a more compact end result.
ADDITIONAL INFO: Both signals when connected to the motor.
PIC signal (without R2), 8.2-11.2V:
NE555 signal, varies 0-12.2V for 500ms and 0-1.32v for 780ms:
In both cases the PWM frequency and duty cycle remain intact, disregarding the voltages.