Hello my friends.
I have written this sketch to my Arduino. It is a very simple PWM signal generator. It works properly.
My scope is telling me that the Pk-Pk voltage is 8.32V ( Pink trace ). You can see the Pk-Pk numbers on the top right corner of the picture below.

How is this possible? It is supposed to be 5 Volts max. Where is the extra 3.32V potential coming from?




void setup() {
}
void loop() {
analogWrite(9, 127);
delay(500);
analogWrite(9, 127);
delay(500);
analogWrite(9, 127);
delay(500);
analogWrite(9, 127);
delay(500);
analogWrite(9, 127);
delay(500);
}

 

I'm guessing that your reference voltage is not what you think it is. Your signal is 5.12 volts above to 1.6 volts below ground. So pk-Pk = 6.72 - (-1.6) = 8.32 V P-P. Seems reasonable to me.

 

I'm guessing that your reference voltage is not what you think it is. Your signal is 5.12 volts above to 1.6 volts below ground. So pk-Pk = 6.72 - (-1.6) = 8.32 V P-P. Seems reasonable to me.

Thank you my friend.What is the minus symbol in front of Duty in the picture? Is it negative Duty cycle?
Does it mean the real Duty cycle is 49.80% ( 100 % - 50.20 %)?

 

Thank you my friend.What is the minus symbol in front of Duty in the picture?
Does it mean the real Duty cycle is 49.80% ?

There are two Duty cycle values and they sum to 100%. I interpret the -Duty to be the low time of the signal and +Duty to be the high time of the signal. What does your scope manual say?

 

What is the minus symbol in front of Duty in the picture? Is it negative Duty cycle?
Does it mean the real Duty cycle is 49.80% ( 100 % - 50.20 %)?

Real signal is not rectangular, but always is trapezoidal,
so it must be difference between duties, measured on top and on base of signal.

 

There are two Duty cycle values and they sum to 100%. I interpret the -Duty to be the low time of the signal and +Duty to be the high time of the signal. What does your scope manual say?

Thank you my friend. The manual says:
+ Duty: Ratio of positive width to period
- Duty: Ratio of negative width to period .
I got the answer.

 

I see:
Top = 4.96V
Base = 0.00V
Ampl = 4.96V