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Squidwrench Electronics Workshop: Session 1

Some ex post facto notes from the first SquidWrench Electronics Workshop, in the expectation we’ll run the series from the start in a while. I should have taken pictures of my scribbles on the whiteboard.

Define:

  • Voltage – symbol E (Electromotive Force or some French phrase), unit V = volt
  • Current – symbol I (French “intensity” or some such), unit A = ampere
  • Resistance – symbol R (“resistance”), unit Ω (capital Greek Omega) = ohm

Introduce Ohm’s Law & permutations, postpone calculations.

Measure the actual voltage of assorted cells & batteries. Identify chemistry, internal wiring:

  • 1.2 = nickel-cadmium or nickel-metal-hydride
  • 1.5 = carbon-zinc or alkaline
  • 2 V = lead-acid
  • 3.0 = primary lithium
  • 3.6 – 3.7 = rechargeable lithium, several variations
  • 4.8 = 4 x 1.2 V
  • 7.2 = 6 x 1.2 V
  • 7.4 = 2 x 3.6 V
  • 9.6 = 8 x 1.2 V
  • 10.8 = 3 x 3.6 V
  • 12 = 6 x 2 V

Measure various resistors, favoring hulking finger-friendly sandstone blocks.

Introduce metric prefixes:

  • Engineering notation uses only multiple-of-three exponents
  • μ = micro = 10-6
  • m = milli = 10-3
  • k = kilo = 103
  • M = mega = 106

Discuss resistor power dissipation vs. size vs. location, postpone power formula.

Clip-lead various resistors to various batteries, measure voltage & current.

Introduce fixed & variable power supplies, repeat resistor measurements.

Now compute permutations of Ohm’s Law using actual data!

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