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lm3916 substitute Answered

im going to build a rgb vu meter but when looking for parts the lm3916 was pretty exspensive and im trying to see if there is a substitute for it     

and a rgb led can two or three of the pins be powered at the same time or only one at a time

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AndyGadgetBest Answer (author)2011-01-07

I'm seeing it on Farnell for $2:50. I'd say that was pretty cheap for the usefulness of the device.

You can power one, two or all three of the LEDs at once, but observe the maximum current for each one.

One thing which you may run up against is because the 3916 is a constant current device, one of the LEDs may be brighter or dimmer than the others if you're colour mixing.  You should be able to put a low series resistor on the brighter one(s) to counteract this.

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AndyGadget (author)AndyGadget2011-01-07

Additionally, if you're running RGB LEDs from a 3916 they will have to be common anode type - i.e. the 'blunt' ends of the diode symbol connected together. Either that or the type of LED with 3 discrete diodes in the package.

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Re-design (author)2011-01-07

I don't know of a cheaper version of the same style chip. YOu can do the same thing using transistors and resistors but it ends up costing quite a bit more than just the chip.

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