Seeing PWM Data

[andrewwynn]

Originally Posted by wpoll

I would expect the PWM signal to be a square wave with a peak value of around 12v. Not sure of the frequency but I'm sure I've heard my (bad) tail light connections "sing" so the frequency is likely within the audible spectrum (20Hz - 20kHz), most likely around a few kHz.



I REALLY need to go and find my Fluke 'scope Meter.... it's on loan to someone and I cannot locate it...

I need to locate mine it's in my basement but I haven't used in years. I've been trying to get an oscope to iPhone interface for years but the ones avail though awesome have as of yet been too limited in voltage range. Eg 20v max input. Too bad!

I'm sure the batteries in the scope meter are quite shot so I'd have to deal with that also.

That said. I need to resolve why my remote fob died and the prime suspect is the receiver/amplifier in the hatch center glass and the test is to watch the output waveform when pressing the key fob button.

I'm thinking I'll swap mine and wife's antenna amplifier and see if I can re-pair my key.

[Zulu95]

The parking et al signal is lower to mimic the lower wattage (7W) bulbs/filaments used for that feature in most vehicles. You only see the full 12V signal for the turn signal feature. This is how they use a single filament to emulate two different wattage bulbs.

[andrewwynn]

My understanding is that the LCM uses PWM to limit voltage to 12v. Eg if the alternator is outputting 13.6v the LCM will set a duty cycle of 12/13.6 =88%

[80stech]

If anyone likes to DIY electronics, check out DSO138 scope kit. I think can be had as cheap as $10 now.

[jsoto]

Originally Posted by andrewwynn

I put lights in for turn signal I had to go back to Incan in front because the led won't come on for running light.

I think this sums it up on what we're seeing due to PWM.

Not to confuse the topic since we're discussing LED rings, but
bearing that, I do so see it could be a challenge with LED turns that are to function as PL/Turns.

I'll have to lookup up old threads but I kinda/sorta remember RB or X5SND saying they redid all to LEDS, IF my memory recalls

[jsoto]

LOL. THIS post. Got me re-looking into adding a scope to the tool chest. Wish vs. want. Decisions, decisions

[upallnight]

You can get an oscilloscope for under $100.00 at Amazon.com.

https://www.amazon.com/Handheld-Osci...81530531&psc=1

I know some people on this thread will balk at spending that kind of money for an oscilloscope/tool. My answer to that is if you don't want to spend the money buying tools or learning how to use a tool, just take the X to a professional.

Here's a video on using an oscilloscope to check out an electrical signal.

https://www.youtube.com/watch?v=PCArn6mm2HA

Flame on, I got my flame suit on.

[andrewwynn]

No "flame" but that particular model similar to the iPhone interface one has a 10v limitation. Most of the inexpensive models are made for digital work at 5v. I did see a bunch of other suggested items and considering the fluke scope meters were well over $1000 that's just plain amazing to see a 90% drop in price (and 97% drop in size).

[upallnight]

Originally Posted by andrewwynn

No "flame" but that particular model similar to the iPhone interface one has a 10v limitation. Most of the inexpensive models are made for digital work at 5v. I did see a bunch of other suggested items and considering the fluke scope meters were well over $1000 that's just plain amazing to see a 90% drop in price (and 97% drop in size).

A lot of the modules on modern cars uses a 5volt reference signal.

[andrewwynn]

Great use of a scope to look for bad commutator. That would work well for starter motor going bad also. Just need the amp clamp to convert amps to mV