HPR4019: Fairy lights and Powerful Pixies

'Twas the night before Christmas, when all through the house Not a creature was stirring, not even a mouse;

OK wrong story.

In his lonely man cave, a HPR Janitor is visited by the ghost of procrastination. Two years later he is again visited, but this time by the ghost of desperation. And then finally by the ghost of rambling.

Today we learn about AC and DC voltage, about Ohms Law and how to wire up a LED to a USB connector.

A long rambling show which in the end came down to using ohms law to find the value of the resister.

Knowing any 2 of the 3 values in Ohms law will give us the resistor we need.

The current will be the same, so we can just measure, and it turns out to be 22 mA (milliamperes) or 0.022 amp. This is measured in Amps, and has the symbol I

The voltage we need to use up is 2 volts as we are going from 5 Volts USB AC Adapter to 3 Volts used by the two AA battery in series. Giving us 2 Volts with unit of V.

We can then find the Resistance measured in Ohms by dividing 2 Volts, by 0.022 Amps to give us 90 Ohms of Resistance.

The V is always on top of the triangle with I and R underneath.

So not having a 90 Ohm resistor a 100 Ohm would work just as well.

• https://www.electronics-tutorials.ws/diode/diode_8.html
• https://en.wikipedia.org/wiki/Light-emitting_diode
• https://www.wolframalpha.com/input?i=.022+amp
• https://www.eevblog.com/forum/projects/smd-led-size-for-beginners/
• https://learn.sparkfun.com/tutorials/light-emitting-diodes-leds/all
• https://www.electronicshub.org/led-light-emitting-diode/
• https://en.wikipedia.org/wiki/Resistor
• https://en.wikipedia.org/wiki/Coulomb
• https://en.wikipedia.org/wiki/Ampere
• https://en.wikipedia.org/wiki/Georg_Ohm
• https://en.wikipedia.org/wiki/Ohm
• https://en.wikipedia.org/wiki/AA_battery

Comments

More Information...