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| Electronic Projects Design/Ideas/Reviews Are you building an electronic project or want to? Maybe you need some assistance? Come and submit your electronic questions here and let our experienced members find a solution. |
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Thread Tools | Display Modes |
16th March 2008, 12:53 PM
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mrfroggy321
Am working with strings of leds, yellow and red. useing a power supply that I built useing a 317T voltage regulator. My problem is when I turn up the voltage to light up the yellow it literally smokes the red leds. My problem is that I need to build a dual voltage power supply, and I need to know what type of mini pot (5k) (as Digi-key shows a gazillion types) to use. Thanks
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16th March 2008, 12:55 PM
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Welcome Mr Frog.
Have you got current limiting resistors in series with your LEDs. Mike. |
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16th March 2008, 11:40 PM
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No resistors, want to stay away from them as there are so many leds and the number will vary from application to application. Thought it would be much simpler going with the 317T's Thanks
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17th March 2008, 01:32 AM
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If you don't use current-limiting resistors with your LEDs then they will smoke and burn.
They are diodes (not light bulbs) with a certain range of voltages. Their current has a max allowed amount. An LM317 can be made into a constant-current-source by adding a single resistor. Then it can light one string of LEDs. An LM317 can be made into a voltage regulator and it can light many strings of LEDs if each string has its own current-limiting resistor.
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Uncle $crooge |
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17th March 2008, 01:40 AM
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Must be avoid resistor night, why anyone would cut out the smallest cheapest part you can get I'll never understand.
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