Introduction: Cheap Voltage Indicator
This is the simplest voltage indicator that you can make with more than one LED.
I have drawn the circuit via:
Another good indicator is shown here:
Supplies
Components, LEDs/bright LEDs - 5, 1 kohm, 2.2 kohm, 4.7 kohm and 10 kohm low power resistors, matrix board.
Tools: pliers, scissors.
Optional Tools: USB Power Supply, wire stripper.
Step 1: Design the Circuit
The maximum current will be across LED1:
IledMax = Vs - Vled / R1 = (12 V - 2 V) / 1000 ohms = 10 mA
Thus the input voltage should not exceed 12 volts.
Step 2: Build and Test the Circuit
You can see my resistor range is from 1 kohms to 4.7 kohms. Not from 1 to 10 kohm. This is why the brightness does not vary much if the input is above only about 5 volts. You can try higher resistor values. However, do not use resistors that are below 1 kohms in value.
