Ice Dispenser Microswitch

Tonight my parents got home from a long drive after dropping me off at college. They were tired and thirsty so they went to the fridge to get a glass of ice water- but nothing came out of the water dispenser. So of course they called me for advice.

This is the same Samsung fridge that had issues with the water line freezing (see our repair video on Youtube about that fix: https://www.youtube.com/watch?v=whjh9TLSnSE), but it didn't sound like that was the problem this time. My dad did some troubleshooting and checked that the light inside the fridge turned off when the door closed and on when it opened. I told my parents to also check whether the light over the dispenser came on when they pressed a cup into the lever. Nothing came on, no lights or sound and no water or ice. But the light did come on when the light button was pressed. That meant it was probably a bad microswitch.

They looked up the model to find out how to unscrew and pry off the front panel. Then they took out the switch and called me back. I walked them through using a multimeter to test the switch. When the switch was pressed, it should have been letting more current through. It should have only measured 2 or 3 ohms, but it was measuring a resistance of several thousand ohms. So I told my dad to look for my drawer labeled "microswitches". He found one that was the same size and shape, just gray instead of black. The old switch was rated for 1A. The new one is rated for 16A, but it doesn't make a difference because this is a low current circuit.

My parents replaced the switch, and now the water and ice dispenser works again. I was able to help them fix it, even though I wasn't there. Maybe they should pay me for the part and a consulting fee.

Analyzing Flickering LED Christmas Lights

 Several years ago, when LEDs were just becoming popular, we bought a bunch of LED Christmas lights. They were OK but not as bright as the old style incandescent ones. They still had issues with bulbs coming loose so half a strand would go out. And of course the usual tangles. 

This year, after Christmas, I decided to buy a new set of LED lights to see if they would be any better. The new LED lights have more colors and are brighter, but seem to be more flickery than the old ones. My mom says that's not a problem- twinkling lights will look good on the tree. But it bothers me. So I decided to look at the wave patterns with my Lighting Analyzer and oscilloscope.

The wave pattern is not a sine wave or a half sine wave- it is pulsing. This explains why it looks flickery. To compare the frequency to 60 Hz, I added an antenna wire wrapped around the oscilloscope power cord (the purple line) because mains power is 60Hz. Next, I tested the old string of LED lights. It turns out that the old strand is exactly the same, just dimmer. So that's why we didn't notice the flicker on the old lights.