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.

^{simulate this circuit – Schematic created using CircuitLab}

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.

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.

^{simulate this circuit – Schematic created using CircuitLab}

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.

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.

^{simulate this circuit – Schematic created using CircuitLab}

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.

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.

^{simulate this circuit – Schematic created using CircuitLab}

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.