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== Unknown voltage of an LED == | == Unknown voltage of an LED == | ||
There are different methods of determining the voltage of an LED. | There are different methods of determining the (forward) voltage of an LED. | ||
If the wave length is | === Knowing The LED's color === | ||
If the wave length is known the minimum voltage to create light can be calculated [http://www.pveducation.org/pvcdrom/properties-of-sunlight/energy-of-photon here] or in this [http://www.oksolar.com/led/led_color_chart.htm LED color chart]) | |||
=== Testing with a Resistor === | |||
If the wave length is unknown the LED can be connected to an adjustable voltage source via a large resistor and the voltage can be gradually increased until a small current flows through the LED (for example 1mA will be ok for all standard LEDs without destroying them). While running this, the voltage across the LED's legs can be measured. The voltage then can be used for calculations. | |||
If you have no variable voltage source: Use any voltage source between 5V and 10V and a 5000 ohm resistor - so the maximum current is less than 2mA in any case. Then measure the voltage across the LED. | |||
=== Testing with Multimeter === | |||
The diode tester of a Multimeter internally works similar to the above described method. The Multimeter uses a small voltage and a limited current (usually between 0.1 and 1mA). It displays the voltage across the diode. Some multimeters deliver sufficient current to light the LED very dim (use a dark environment). | |||
However this doesn't work for all diode testers I have used before - they may only be able to detect voltages up to 1.5V for example - a blue LED (3V) can't be tested this way. Best try with a white LED if it works with your multimeter. If this works it will be fine with all standard LEDs as well. | |||
== Links == | == Links == | ||