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LED Indicators

When using a Light Emitting Diode (LED) as an indicator, use the following formula to determine series resistance for various voltages: R = (E - 1.7) x 1000/I, where R is the resistance in ohms, E is the supply voltage (DC) and I is the LED current in milliamps.

Eg. to operate the LED at 20mA, for 6V, use 220 ohms

9V  - use 390 ohms.
12V - use 560 ohms
24V - use 1.2k ohms

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