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Lab 3: It’s electric!

NTS: The soldering irons in the lab suck.

I borrowed Aaron’s “12V” DC power supply, in quotes because it actually outputs 17V!

The voltage regulator, however, does it’s job and outputs pretty close to 5V.

With two LEDs in series and no resistor, I measured a voltage drop of 2.47V across one LED and an almost identical drop of 2.52V across the other. I’m assuming they didn’t burn out because each acts as a resistor for the other.

It was too hard to use the multimeter while holding down a push button, so I replaced it with a switch that would stay on or off without my intervention.

A mistake when wiring in series.

Though initially my LEDs lit up erratically as shown above, I realized that I had wired both pins of the second into ground and corrected the problem. The three LEDs then didn’t light up because they split 5V three ways and apparently 1.7V will not power an LED of this kind.

I measured the 4.97V across all three LEDs when wired in parallel but my voltage regulator overheated (smelled not good) and suddenly the voltage dropped to 3V (measured across the voltage regulator as well as the LEDs). I let it cool off and it resumed normal operation.

I had to twist wires around my meter probes because they wouldn’t fit in the board—this also made taking pictures much easier!

The pot did not increase and decrease voltage particularly smoothly. It jumped from 3V to maximum (4.7V or so) right at the end. I tried another pot and it behaved the same. I’m not sure why this is. It could because people perceive volume and other things that are traditionally controlled using potentiometers logarithmically. It could also have a purely physical explanation that has to do with the material out of which the resistive material in the pot’s innards. In any case, I’m not sure I’ve figured out this particular puzzle, but electronics in general is seeming a whole lot less puzzling.


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