Hello everyone! Anyone who just doesn't seem to have the right scale when needed should read this post, because it can save you time and money. eBay sellers and occasional postcard senders will find it useful especially when they are in emergency.
This is not a high tech project, nor does it involve high tech components. In fact, it is a very simple project that works every time!
It involves a coat hanger, some threads, a wooden stick, some weight, a solder piece and your imagination. Again, if you look at the photos, these components are not strictly required. You can mix and match with what you have in your junk box. The important thing is that you get the basic principle right.
A weight hanging from a thread or rope makes the thread or rope absolute vertical with reference to the Earth's horizontal plane. I don't know who found out about that first. Does anyone know?
Step 1: Hang a Weight and a Piece of Solder at the Center
First, find a suitable coat hanger that should support the weight that will be hanging underneath it later.
Then, find the center of gravity of the coat hanger (doesn't need to be exactly!). There, tie a weight with a thread (in my case, a wall plug).
On top of it, tie a solder piece. Just wrap around it. You can also use a piece of copper wire or something, as long as it is flexible enough to calibrate.
Step 2: Place the Scale on a Wooden Stick or a Metal Bar
Place (hang) the whole assembly on a wooden stick or a small metal bar.
Then, hang two equal weight at the ends of the coat hanger.
Step 3: Calibrate and Use the Scale
Look at the scale from the front.
Calibrate the solder piece or copper wire to be in parallel with the hanging thread.
Here is how to do this easily:
Take your position in front of the scale and have a reference point behind it; possibly on the wall behind it.
Align your eyes, the solder piece, the thread behind it and the reference point straight.
If the solder piece is not alligned straight, then use your hand to bend it a little bit so that it stays straight and in parallel with the thread.
Everytime when you look at the scale, you have to look at it from roughly the same point. That's it.
Now you can hang whatever you want at one end and just hang some known weight such as coins at the other end, and work out the near exact weight of your item. In this way, I've found out 9 Toshiba Satellite laptop keys and its 9 latches are roughly equal to 3 pennies. Not bad at all! You may need to wait a bit until the scale is stable to read it.
Scale it up or down with your imagination and you can have a better one than mine.
Have a happy DIY!