Sunday, October 3, 2010

Design, Even in a Toothpaste Tube

This is one of my sillier endeavors but I think it will make sense to those other like-minded engineers/designers out there.

So, I have a pet peeve: wasting toothpaste at the end of the life of the tube. It bugs me when there's something leftover in any type of container for that matter. But I deal with toothpaste on a daily basis so it is a perpetual nuisance. The solid exoskeleton toothpaste containers seem like they're even worse than the soft tubes that you could squeeze or roll until you're blue in the face.

A couple of days ago I was getting to the end of another solid tube and the frustration got to the point that I had to take it apart just to see how much I was wasting. So I got my exacto and tore into it. To my surprise there was only a small glob of toothpaste at the very tip, only a single toothbrushing-worth.

It had felt like much more than that, not to mention I didn't know how it was possible to have that little in the rest of the foil-like sack. I was about to chock it up to "who knows" when I noticed something on the base.

That's right, whoever designed this achieved a one-way valve with a tiny piece of plastic and a heat-weld with a couple small interruptions for air to pass in only one direction. That allowed it to squeeze as much as possible out of the toothpaste sack. Something so cheap and simple yet innovative to solve man's toothpaste dispensing needs. It's the small things in life :).

Refrigerator Compressor Repair

This Alabamian gave me a non-working wine cooler mini-fridge, half out of generosity because I might be able to fix and use it, half out of wanting to get rid of it :-).

Regardless, I've had this fridge sitting in the middle of my apartment now for the better part of a month. It haunts me every time I walk by it. Sitting there... not working... taking up space. I finally had time this weekend to troubleshoot it.

After plugging it in,the compressor would hum for 15-20 seconds and then there would be a click and it would be silent for about two and half minutes. Then it would click and the cycle would repeat itself. I let this go on for about 15 minutes while I monitored the temperature inside the fridge. There was no change inside but the compressor was almost too hot to touch. So began the troubleshooting.

I took off the condenser (panel of tubes on the back), removed the thermostat housing and finally pulled out the compressor.

I had to bend some of the brass tubes in the process, being careful not to kink them. All that was let was to pull off a cover exposing the relay and circuitry for the compressor.

The first step was to bypass the thermostat, sending an "always on" to the compressor to eliminate that as a potential problem. Here is the thermostat with the dial and cover removed.


Making sure to not touch any of the exposed contacts I plugged it in again. Same result, so I did a little Google searching and found a convenient How to Test a Refrigerator Compressor article. The takaway from that and a few other forums with posters with similar symptoms was that its either a bad relay, overload protector or compressor. If the compressor is gone then I'm hosed so I decided to check the relay and overload protector.

The overload protector is the small black plastic housing attached to two terminals protruding from the compressor housing. (P6R8MC OR0510, just in case someone searches) The common wire attaches to the overload protector. After taking it off this is that it looks like.

Now after removing the metal securing strip and the cover.

You can see a strange white disc shape that separates the two sides.

As you can see, the two sides of the disc are in different condition. One looks like it has been shocked/burnt and the other is only slightly scratched. I think this disc acts as either a sort of discharge capacitor or a large overload resistor.

Either way, I decided to flip it and put it back in the overload protector. Voila! Whatever contact or circuit that is supposed to make wasn't being made on the destroyed side. Within 20 minutes the fridge was down to 40 degrees! Hopefully this will provide others with some DIY troubleshooting inspiration. And thanks to the Alabamian for the (now working) fridge!