Archive for May 16th, 2018
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.
- 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.
Now compute permutations of Ohm’s Law using actual data!