Fix: Computer mouse

Received broken ps2 mouse from friend. It's broken cos he seriously twisted up the 6 ps2 pins, don't know how. It's got a very nice scroll wheel, so figured it's worth fixing.

Removed the entire mouse cord and replaced with a working cord scrapped from an old ps2 keyboard. The color code on the internal wires were different, so it took some funny/annoying trial and error to determine which wires controlled the horizontal and vertical movements as well as left/right click.

Soldered the right wires together, used electrical tape to tape off the exposed wiring. Works great, although mouse now has purple ps2 connector, like a keyboard, lol.

PS - for April fool's joke, switch the wires inside a friend's mouse.

Fix: computer speaker sets

Found 2 identical speaker sets in the e-waste. (EP-691H Multi-Media Amplified Speaker System)

Inital test: One speaker set works perfectly fine. The right speaker on the second set doesn't work and the left speaker works (loudly) only when the volume dial is turned to max.

Opened up both sets to reveal what appeared to be the same thing. There were no bulging capacitors on either board. Tested the bad speaker set's right speaker on the good set, and it turned out that the right speaker itself was fine.

Ran my fingers along the bottom of the circuit board, causing the bad left speaker to emit funny cool noises like R2D2. (aka circuit bending) Interestingly, circuit bending the boards of both speaker sets caused similar noises to emit. Therefore I figured that the left speaker was most likely working, so redirected my attention to the board itself.

After circuit bending and playing with the volume dial for over an hour in frustration and fun, I finally decided to pull out my multimeter to test the potentiometer.

Observed:
Pot controls left and right speakers separately (separate circuit leads)

When vol dial(pot) turned from min to max,
Good set's pot: Both leads go from 9.5kohm up to ~13kohm for a bit then linearly back down to about 4 ohms

Bad set's pot: Top lead: 12kohm up to 50kohm then drops SHARPLY to a few ohms, near "max volume"  Bottom lead stays at ~38Mohm.




Results:
- The pots from the two sets behave very differently.
- Resistance and Volume are have an inverse relationship.
- The behaviour of the bad pot's top and bottom leads corresponds exactly to the results of the Initial Test.
Top lead's sharp drop causes left speaker to suddenly have max sound near max volume and stay mute otherwise. Bottom lead stays at a constant high resistance(Mohms), causing no sound on the right speaker, regardless of pot position.

As expected, shorting the top and bottom leads caused max sound on left and right speakers regardless of pot position.



Conclusion
bad potentiometer, need a 9kohm to 4ohm resistor to fix.

"Dead" Batteries Part 1

It all started when a friend needed 4 AAA batteries for his classroom clicker. We had no spares so I fished some out from the battery drop-off boxes scattered across campus, hoping to get very lucky. As expected, the clicker wouldn't start up with those batteries because they were supposedly dead.

But I had a nagging suspicion that there were a few batteries in that huge drop-off box with enough charge to power that clicker for at at least a few minutes. Or at least cause that bunny to hit the drum once.


I pulled about 20 AAs from the bin to test my clock(takes single AA, 1.5V) and found that just under half of them could power my quartz clock. Of the rest, a few could only move the minute hand from 12 to 7, and a few more could cause the minute hand to vibrate every second. Only about a quarter of the 20 did absolutely nothing when plugged into clock.

And even the "weak, 12 to 7 tickers" were able to power my clock for 3 weeks when the clock is left flat on the ground. (less gravity to overcome)

This proved to be an interesting and potentially useful discovery. I randomly collected a total of 421 batteries across various locations on campus. Then I used a voltmeter to test and categorize each battery according to its measured voltage and its battery type. Five types of batteries were collected: AAA, AA, C, D, and 9V.

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AAA Batteries (1.5V):

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AA Batteries (1.5V):

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C Batteries (1.5V):

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D Batteries (1.5V):

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9V Batteries:

About

Welcome to Zero Money Tech.

The main purpose of this blog is to document the adventures of a poor student who is trying to save money by re-using or re-designing discarded consumer technology. Interesting facts learned and ideas developed along the way will also be documented.

This should be fun.