inconsistent bi-color bargraph

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joefly
 
Posts: 15
Joined: Wed Oct 24, 2012 10:54 am

inconsistent bi-color bargraph

Post by joefly »

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.?

adafruit
 
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Joined: Thu Apr 06, 2006 4:21 pm

Re: inconsistent bi-color bargraph

Post by adafruit »

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!

joefly
 
Posts: 15
Joined: Wed Oct 24, 2012 10:54 am

Re: inconsistent bi-color bargraph

Post by joefly »

Which resistor do you recommend?

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: inconsistent bi-color bargraph

Post by adafruit »

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