Modeling an HO gauge freelance version of the Union Pacific Oregon Short Line and the Utah Railway around 1957 in a world where Pirates from the Great Salt Lake founded Ogden, UT.
- Photo album of layout construction -
Those results look good. Note that you can have up to a ±10% resistor tolerance and they will still be over the 70 Ohm that was calculated.
If you are interested in the equations used, they are:
Vs - Vf = IR and P=IV where Vs is the supply voltage and Vf is the diode forward voltage.Remember that the LED's long leg is the (+) pin!
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
I am installing about 50 occupancy zones using seven RR-Cirkits BOD-8 and seven FOB-A boards. The FOB-A boards each have 8 spots where resistors can be soldered for outputs that drive display panel LED lights. I have measured the voltage supplied to these outputs and it is 3.1 volts.
Based upon this resistor calculator using input voltage=3.1, LED voltage drop (red LEDs)=1.7v, and desired LED current=20 milli amp it says to use 82 ohm 1/8 watt resistors.
I have tested with an 82 ohm resistor and it works, but before I solder 50+ resistors onto FOB-A boards I was hoping to get confirmation of the calculator results?
Thanks.