01-21-2023, 02:22 AM
(01-21-2023, 01:15 AM)TerryRitchie Wrote: I thought the formula for resistors in parallel is 1/R1 + 1/R2 + 1/R3 ...
That's what I was taught in electronics class during my aviation electronics (avionics) training in the Marine Corps.
The basic 2 value formula is (X1 x X2) / (X1 + X2) to give a parallel total value. Which could be used for 3 and more. Repeat add nauseous.
When finding the value for 3 or more. It's what you were taught in the Marines. Using reciprocals, is such a pain in the ass without a calculator. The program I presented can find the total or a missing single value. I created the program to find the R2 value of a simple R1, R2 circuit. Unfortunately R2 could not be a normal sold value. So a 20 turn pot of X value with a fixed resistor of the major value was used. The circuit was a CC source power supply. So a tweaking was going to be needed.
What you learned is not wrong, just harder. Remember the two value formula, when it's only two parts. Even without a calculator it's faster.