Archive for July, 2011

First stab with my DSO Quad – 12v dimmer experiments

Posted in DSO Quad, electronics on July 20, 2011 by makingthingswork

In our living room we have some ikea cable lights and we replaced their transformer based driver with a switching one.. I forget what model it is but it looks a lot like a laptop power brick. Anyways, we’ve had it for years, but i always got the feeling that it wasn’t as bright as it should be.

I just got a Digital storage oscilliscope, so I decided to take a look and see what the deal was.

In this case i knew the RMS voltage is 12v, which is a peak-to-peak voltage of around 35v. I checked, and my scope can handle up to 80v.

There are 2 main components to the lighting system:
* wall dimmer, which is an insteon 6 button keypad
* 12v driver, which is up in the attic and takes the 120v from the switch and drives 12v to the lights.

I am pretty sure the wall dimmer is the kind that chops the AC waveform at the leading edge, so i expected to see the waveform in the scope be sort of a truncated SIN wave.

What i saw when i started was a truncated sin wave, but it also itself was made up of a nice sin wave. That must be a function of the 12v controller. Curious indeed.

As i increased the brightness, the overall sin shape returned almost all the way, but the sub-wave remained. The main sin wave never became fully ‘on’.. I think this is caused by the wall-dimmer i have.

check out the traces:

The last trace is zoomed in more than the previous 3.