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RE: LED Indicators

Posted by : James - Edinburgh- (94.11.26.59)

Inappropriate or SPAM?
On Monday 29/10/12 at 18:30:08

I don't think it needs a 'load' resistor, more of a current limiting resistor as you do not want too much current to flow through the LED. To calculate the value of R in series with the LED you need to know the optimum current flow for the LED at a specific Voltage (from the item's data or spec sheet). Then you will know how much voltage needs to be dropped across the resistor and the current that flows through the resistor is the same as the current through the LED.

I have no idea what the figures are but supposing the LED drops 3V at a current of 20mA. Assuming a 12V battery the resistor must drop 9V with the same current and R= V/I =9/.02 = 450 ohms.

The resistor must have the correct power rating. P=IxIxR = 0.02 x 0.02 x 450 =0.18W.

The price of those LEDS means you don't want to make a mistake so make sure you get that data sheet.

Message Thread:

LED Indicators - Kebob Fri 26/10/12 at 00:52:12

RE: LED Indicators - Kebob Fri 26/10/12 at 01:31:41

RE: LED Indicators - Boo Fri 26/10/12 at 02:18:02

RE: LED Indicators - WiganBob Fri 26/10/12 at 02:30:17

RE: LED Indicators - andy Fri 26/10/12 at 02:45:09
RE: LED Indicators - Boo Fri 26/10/12 at 04:49:23

RE: LED Indicators - WiganBob Fri 26/10/12 at 13:43:11
RE: LED Indicators - Diesel Fri 26/10/12 at 13:43:51

RE: LED Indicators - WiganBob Fri 26/10/12 at 18:41:23

RE: LED Indicators - James - Edinburgh- Mon 29/10/12 at 18:30:08

RE: LED Indicators - Boo Tue 30/10/12 at 00:02:31

RE: LED Indicators - Kebob Tue 30/10/12 at 01:31:48

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