How to test if PWM mode is working correcly?

Question

I d'like to test if the PWM mode is working correctly on the pins of my Arduino Board. Do you know a simple schema to do this ?

Answer 1

There are my options:

• The default way to do this is to use an oscilloscope. These can be quite expensive.
• Use a logic analyzer if the voltage is logic/binary (0 and 3.3 or 5V). These are very cheap.
• The easiest way to know if it works without the devices above, is to lower the speed drastically (using a divider in the software, like 1000 or more to get PWM widths of 100 ms to multiple seconds) and connect the PWM output with a resistor and a LED to GND. If the LED flashes faster, the PWM speed is high, otherwise low. By using a stopwatch you can roughly calculate the PWM speed (taking the divider into account) and after the test remove the divider.
• If the PWM is controlled completely from your Arduino (probably not), you can use a software counter and print it out afterwards to see the speed.

• snoob dogg: ha ! I knew that this cheap Chinese oscillator i bought one day could finally be useful at something. thank you
• Michel Keijzers: Do you have a DSO150 (analog?) scope or a digital logic analyzer? Last are really easy (and much faster, 8 channels) and cost less than 10 dollars.
• snoob dogg: this is a DSO Shell from JYE Tech , really cheap and poor but should to the job :)
• Michel Keijzers: Sounds good, I don't have such a digital oscilloscope but planning to get one eventually. I have a very old analog one but it is very hard to use (bad CRT). Anyway with your oscilloscope it should be possible to find out the PWM speed.
• snoob dogg: I just tried it and my PWM works correctly : )

Answer 2

You could just do a simple analogWrite, varying the duty cycle, with an LED/resistor. Fade the value up & down, see if the LED gets brighter & dimmer.