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Author Topic: Need help choosing the right resistor for 7 segment LED display.  (Read 1314 times)
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I recently bought 3 7 segment RED Led displays. I don't know which resistor value to use as to how much current and voltage they operate on. They had the number "RCCH101" printed on them. I was afraid I would burn them, so I did not experiment with them. Can you please help me with this. I know a bit about electronics, but this is the first time I am using a 7 segment display. Please help me out.
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Plz give more info like the Volts and current for LED and the source voltage
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In my opinion, most 7 segment display work fine with a limiting resistor of 220, 330 and 470 ohms for each segment. I prefer 330 ohms to 470 ohms. If I want to cutdown the current being use of my project, I use 470 ohms, it bright enought, safe for any High digital output. <-- for a commun cathode anyway. Same for a commun anode, because the display is control by a transistor - TO-92 type ,and I want to keep the total ( segment current * eight ) under 100 mA.
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Plz give more info like the Volts and current for LED and the source voltage

That's the whole problem. I don't know. Any way thanks to both of you for helping me out.

Can you also give me the curret and voltage that should be applied to a 7 segment display RED normally. 
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Red displays typically take up 10 to 20mA per segment and drop around 1.2v or a little more. So if you are using a 5v supply, I suggest you try a series resistor in the range 390 ohms to 180 ohms on each segment - more or less the same as Techone suggested.
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red are typically 1.8V or so.  1.2V would be an infra-red LED.
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My "standard" limiting resistor for any led's in general, I use 330 ohms. And it is a commun value. In my final design on a PCB board, I use 470 ohms. I don't mind a bit less bright, a led on a display is just "display" not light up your room... And it help the overall current of my project to be lower which is good for the regulator and the control transistor of the 7 segment display. 
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