inconsistent bi-color bargraph
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inconsistent bi-color bargraph

by joefly on Fri Nov 16, 2012 12:35 pm

Hi, I bought 3 bi-color LED bargraphs. I have hooked it up to a raspberry pi, using MCP23017 and using 470ohm resistors along with 3 PNPs. The circuits and program seems to work fine. However, some leds are fully lit and others are dim. When I swap out the bargraph LED, the same problems but different leds on the bargraph are dimmer or brighter. If I, replug the bargraph, same pattern of dim and bright. But different patterns with different bargraphs. Everything else is the same, but different results with different bargraphs.

So I am thinking are they defective? But I seem to be able to get those dimmly lit LED straight to battery of 3v.

any suggestions on if the bargraphs are defective or something wrong with my circuit components.?
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Re: inconsistent bi-color bargraph

by adafruit on Fri Nov 16, 2012 8:39 pm

you could try lighting up each LED seperatly using a resistor, +5V and ground, see if they appear different. the bargraphs are pretty good quality so its unlikely the colors differ - but don't burn out the LEDs either!
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Re: inconsistent bi-color bargraph

by joefly on Sat Nov 17, 2012 12:29 am

Which resistor do you recommend?
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Re: inconsistent bi-color bargraph

by adafruit on Sat Nov 17, 2012 1:33 pm

1K
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