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I was wondering what would you get on subtracting a 12V (From 0 to 12V) PWM (50% duty cycle), from a 12V constant DC source?
I am sorry, english is not my first language. I mean that if from an arduino or a comparator, we connect the output pwm to a motor, and other side of the motor to a 12V source, then what kind of voltage drop can we expect across the resistor.
I was wondering what would you get on subtracting a 12V (From 0 to 12V) PWM (50% duty cycle), from a 12V constant DC source?
Well half the time you'd get 0V (12V - 12V = 0V) and the rest of the time you'd get 12V (12V - 0V = 12V).
In fact what the subtraction does is invert the squarewave about a mean level of 6V but, because it has a 50% duty cycle it looks exactly the same.
If instead you had a 30% duty cycle (12V 30% of the time) you'd end up with a waveform that has 12V 70% of the time.
First, if you're going to drive a 12V motor with an Arduino PWM pin, you need to do something like this.
simulate this circuit – Schematic created using CircuitLab
The voltage across the motor will be 0V at 0% duty cyle, 12V at 100%, and 6V at 50%. That relationship is about as close to linear as the real world gets.
12 PWM (50% duty cycle)? If the peak-to-peak voltage 12 V or is the effective voltage 12 V? Either way, you'll get a square wave, but how exactly it will look like depends on the waveform of that12 PWM (50% duty cycle). \$\endgroup\$