Group Actions
Engagement
  • Author Author: ntewinkel
  • Date Created: Date Created
  • Views 1300 views
  • Likes 13 likes
  • Comments 6 comments
Related
Recommended

Learning to 'scope with Multicomp

ntewinkel

I recently received a Multicomp MP720015 from element14 as part of a contest prize. It's a very nice little unit, but I know nothing about oscilloscopes so it's a learning curve. I mean a learning opportunity Smile

Luckily for me, was kind enough to produce a few videos and blogs about the subject! Thank you James! your tutorials are exactly what I needed Slight smile

So I pulled out an extra Arduino Uno I have here to get the very first basic pattern to test: the Blink sketch.
(I don't recall if I had to speed up the blinking to get this result)

image

Turns out that gives a nice easy square wave (? is that the term?) to look at. Yay it works!

Then I tried with AnalogWrite, as James did in his video, and all I got was muckymuck garbage to look at. hmm... why?
I gave up that evening as it was getting late, but later realized it was likely because I was using pin D13 which has the built-in LED on it. I specifically used it so I could see the LED at the same time as the scope result, but I think it was affecting the output voltage levels. Yes, I did press the auto-set button a few times without luck.

So today I changed the sketch to use pin 9, and success! I can now see how PWM looks:

image

Scope showing Arduino AnalogWrite

I haven't had any luck trying to scope fading with analogWrite, and I don't know if that's a limitation with the scope or with the user :D

Fun start though.

I also tried out the DMM (multimeter) functions, and it appears to be nice, stable, and accurate. It does take much longer to start up than my regular multimeters, so for quick one-off readings I'll likely just use those. For more involved work I can see it being useful especially when also using the scope functions.

-Nico

Parents

  • Heads up, pin 13 does NOT support analogWrite(). If you go peer inside of the function's code (line 276), you'll find that on non-PWM pins, it just turns the pin ON or OFF based on the value you passed. As you found out, Pin 9 does support analogWrite()! (Look at the silkscreen for the pins. Any pin with a ~ character supports PWM.)

    Also, I'm glad the tutorials helped. I really hoped people would be able to see examples of real measurements they could make, regardless of the scope they have!

Comment

  • Heads up, pin 13 does NOT support analogWrite(). If you go peer inside of the function's code (line 276), you'll find that on non-PWM pins, it just turns the pin ON or OFF based on the value you passed. As you found out, Pin 9 does support analogWrite()! (Look at the silkscreen for the pins. Any pin with a ~ character supports PWM.)

    Also, I'm glad the tutorials helped. I really hoped people would be able to see examples of real measurements they could make, regardless of the scope they have!

Children
  • in reply to baldengineer

    > "Heads up, pin 13 does NOT support analogWrite()"

    Aaahhhhh. ok that makes a lot more sense now - I wondered why the LED would make that big a difference. I forgot about that detail of not all pins supporting PWM.

    Thanks for the clarification Slight smile

    edit: you know, the funny thing is that for pin 9 I specifically verified that it was capable of PWM (checking for the ~ as you mentioned), but I totally failed to think of looking at D13 for that detail Face palm