Ok- let me begin by saying I know very little about electronics but am very intrigued by them.
Here is what I know at this point...
I have a variable pwm signal with a 2-3 amp maximum output to control dc motor speed. It is able to switch polarity on command from a switch to reverse the dc motor and then vary speed in the opposite direction. I would like to modify the motor speed further after the pwm signal. The motor has a resistance of about 3 ohms if this is relevant.
My first approach was simply to start over from scratch as I know little about how the existing pwm signal is generated and build my own switching polarity pwm signal using a hex inverter with a schmitt trigger, and a resistor and transistor for the high output as http://www.robotroom.com/PWM.html elegantly describes.
Now that I have ordered the materials and am trying to assemble the circuit (breadboard soldering beyond the experimentor board is not my expertise), wouldn't it be a lot easier to just use some sort of adjustable rc filter or maybe just a potentiometer to modify the signal I have? For example if I have a 50% duty cycle 5 volts which creates an effective 2.5 volts pwm to the motor, can I add a variable resistor to the pwm output before the motor to make each pulse say 4.8 or 4 volts to an effective 2.4 or 2 volts to the motor?
I think I understand the reason to use pwm over a simple potentiometer is to not stall the motor and for less power consumption/heat generation- so I am reversing all of these benefits by adding the pot after? I read about rc filters one pole, two pole etc but got a bit confused on those as well- they seemed right for my application but I didn't see how to make one variable.
If I were to run a high amp pwm output into a hex inverter schmitt trigger pwm afterwards to modulate the modulation I would fry it correct?
I apologize if I have confused you as the reader as I believe I have now confused myself further!
Thanks!
Here is what I know at this point...
I have a variable pwm signal with a 2-3 amp maximum output to control dc motor speed. It is able to switch polarity on command from a switch to reverse the dc motor and then vary speed in the opposite direction. I would like to modify the motor speed further after the pwm signal. The motor has a resistance of about 3 ohms if this is relevant.
My first approach was simply to start over from scratch as I know little about how the existing pwm signal is generated and build my own switching polarity pwm signal using a hex inverter with a schmitt trigger, and a resistor and transistor for the high output as http://www.robotroom.com/PWM.html elegantly describes.
Now that I have ordered the materials and am trying to assemble the circuit (breadboard soldering beyond the experimentor board is not my expertise), wouldn't it be a lot easier to just use some sort of adjustable rc filter or maybe just a potentiometer to modify the signal I have? For example if I have a 50% duty cycle 5 volts which creates an effective 2.5 volts pwm to the motor, can I add a variable resistor to the pwm output before the motor to make each pulse say 4.8 or 4 volts to an effective 2.4 or 2 volts to the motor?
I think I understand the reason to use pwm over a simple potentiometer is to not stall the motor and for less power consumption/heat generation- so I am reversing all of these benefits by adding the pot after? I read about rc filters one pole, two pole etc but got a bit confused on those as well- they seemed right for my application but I didn't see how to make one variable.
If I were to run a high amp pwm output into a hex inverter schmitt trigger pwm afterwards to modulate the modulation I would fry it correct?
I apologize if I have confused you as the reader as I believe I have now confused myself further!
Thanks!
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