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08-11-2003, 12:29 PM
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#1 (permalink)
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LED voltages?
I opened up my IS-22 Canon Scanner Cartridge for fun and applied 6V to the little LEDs that are on it, and they lit up VERY VERY BRIGHT, but they didn't burn out. Does anyone know what the recommended voltage is for these LEDs? I just want to mess with them see if I can put them on my computer as decoration. They are in White casing, not like regular LEDs.
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08-11-2003, 12:39 PM
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#2 (permalink)
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If the LEDs are all one plastic part, look for markings on that plastic casing, then search for the info from the markings, to get a component datasheet. Otherwise, you'll need a schematic to read the system voltages, and maybe that will tell you.
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08-11-2003, 12:41 PM
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#3 (permalink)
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No, they are actually in what feels like ceramic, and it's not one big thing, its 5 seperate LEDs.
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08-11-2003, 12:50 PM
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#4 (permalink)
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I think most of them run at 3V
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08-11-2003, 12:51 PM
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#5 (permalink)
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LED's typically should have about 10mA - 20mA flowing through them for normal operation. This means if you use a 6V PS you would want to place about a 300 ohm resistor in series with the LED. You don't want to power the LED directly without a resistor or you will fry it, unless this LED has a built in current limiting resistor.
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08-11-2003, 01:13 PM
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#6 (permalink)
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Well, I had the 6V on it for about 30 seconds and they didn't fry, but I still don't think they should be that bright. I'll try the 300ohm resistor, thanks!
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08-11-2003, 01:33 PM
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#7 (permalink)
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Its possible it may be rated at 3V (as Telexen post) with a built in current limiting resistor, but when you supply double the voultage, you double the current and it gets really bright. You may want to experiment with the resitor value to get the exact brightness you prefer.
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08-11-2003, 02:04 PM
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#8 (permalink)
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It WILL burn out eventually if you're appling too much voltage, i've had it happen to me with a few LED's... I know the LED's on my case run off the 3.3 volt rail.
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08-12-2003, 05:48 AM
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#9 (permalink)
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LEDs want to set their own voltage, and will burn out of you force too much voltage across them. Assuming that most LEDs are a single voltage is not going to work in every situation: some LEDs have resistors built in, and are set up to work from a specific voltage, such as LEDs which are set up for 12V - those will not work at all at 3v, per Telexens post.
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