2019-09 "AstroAI Digital Multimeter, TRMS 6000 Counts Multimeters Manual and Auto Ranging; Measures Voltage, Current, Resistance, Continuity, Capacitance, Frequency; Tests Diodes, Transistors, Temperature, Red" www.amazon.co.uk/dp/B071JL6LLL (archive). Manual: web.archive.org/web/20190904200759/https://static.astroai.com/manual/Astroai-Digital-Multimeter,-Trms-6000-Counts-User-Manual-en.pdf. www.youtube.com/watch?v=uDGCs1G0Tx8 AstroAI WH5000A Digital Multimeter some basic features
2022-10 ELEGOO Upgraded Electronics Fun Kit www.elegoo.com/products/elegoo-electronics-fun-kits-4-versions Manuals:
Breadboard power supply module MB‐V2:
  • Input voltage: 6.5-9v (DC) via 5.5mm x 2.1mm plug
  • Output voltage: 3.3V/5v
  • Maximum output current: 700 mA
TODO center positive or center negative?
Does not come with AC adapter, getting this one: www.amazon.co.uk/dp/B08ZN476FW output: DC 9V 1A Power Supply Adapter, Plug 5.5mm x 2.1mm, Center Positive,B rand: Security-01, input: AC 100-240V 50/60 Hz, Cable length: 1.8m
LEDs:
  • maximum Continuous Forward Current: 50 mA
  • under 20 mA
    • Forward Voltage: 2.0 V typical, 2.5 V max
20 mA appears to be the typical operation. So with the 2.0 V drop on 5 V power we want a resistor such that:
for the max 50 mA we would instead have 60 Ohms
Bought in the late 2010s.