You can make a simple dual intensity LED light by varying the current through the LED. Light intensity is roughly proportional to the amount of current supplied to the LED. As the current increases, the light intensity increases up to the maximum current limitation of the LED. Current through a green LED can vary between 0 and 20 milliamps. A simple dual intensity LED driver just requires a means to switch between two current limiting resistors.
- Skill level:
Things you need
- DC power supply
- Single pole double throw switch
- Solderless breadboard
- 2 resistors
Find the minimum voltage required to turn on the LED (forward voltage) and the normal operating current (forward current) of the LED from the specification sheet for the LED you plan to use.
Subtract the forward voltage of the LED from the supply voltage and divide the result by the forward current to calculate the series limiting resistor value required for the maximum brightness. This will be at maximum forward current. Choose a standard resistor that is closest to this value.
Calculate the resistance value required for dimmer LED brightness by dividing the resistance value by one half and choosing a standard resistor that is closest to this value.
Connect one lead from each of the resistors to the power strip at the top of the breadboard.
Connect the free lead of each of the resistors to one of the terminals of the SPDT switch.
Connect the common terminal of the SPDT switch to the positive lead (usually the longest of the two leads) of the LED.
Connect the negative lead of the LED to the ground strip at the bottom of the breadboard.
Connect the positive terminal of the power supply to the supply strip of the breadboard.
Connect the negative terminal of the power supply to the ground strip of the breadboard.
Toggle the switch to vary the LED brightness.
Tips and warnings
- You should initially build this on a solderless breadboard for testing.
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