To light my model, I decided to use LEDs and a common DC voltage source (5Volts) from a USB charging socket. I stripped a USB cable to find and check which coloured wire carried the 5V. It's the red wire.
The LEDs I am using have a 3V drop and use 20 milliamps (mA). The following formula calculates the load resistor value to use to drop the 5v to the required 3V at 20mA. It turns out to be 100 ohms. To dim the LED I decided to use a variable resistor up to 10x the load resistor (i.e., 1k ohms), which worked well in my past 'aged' projects.
To my surprise, I discovered that LEDs are much brighter these days! I needed to increase the resistor values by 10 times to get a reasonable dimming effect.
Now the R=1k ohms and VR=10k ohms.
The LEDs I am using have a 3V drop and use 20 milliamps (mA). The following formula calculates the load resistor value to use to drop the 5v to the required 3V at 20mA. It turns out to be 100 ohms. To dim the LED I decided to use a variable resistor up to 10x the load resistor (i.e., 1k ohms), which worked well in my past 'aged' projects.
To my surprise, I discovered that LEDs are much brighter these days! I needed to increase the resistor values by 10 times to get a reasonable dimming effect.
Now the R=1k ohms and VR=10k ohms.
