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bi-colour transistor circuit

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qweets

Sep 26, 2010
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hi, i made this bi led circuit below so that an arduino with 2 pins can change a single led
from red to green and off.

allthough it works great. I think my resistor values are a too low and may harm the transistors over time, yet when i raise the values the bi-led becomes duller.

here below is the circuit runing from a 5v regulated circuit ,
led spec:
Maximum Forward Current 25/30mA
Maximum Forward Voltage per Colour 2.5V

i wonder do these resistor values look o.k?

one objective was to make a small footprint.

Thanks for your help : )

bicolor.jpg
 
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qweets

Sep 26, 2010
48
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Sep 26, 2010
Messages
48
topic closed ,

I had a question here regarding a circuit but found out the problem was simply that a rogue transistor found its way into my 2n3904 bag. luckly i had my magnifying glass close at hand.
: )
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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Jan 21, 2010
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25,510
It seems overly complex.

Just having the 2 pins driving individual transistors that switch a diode on and off would appear to be essentially equivalent as long as you're controlling the uC and you're not converting some particular bit pattern to the LED behaviour in a non-trivial way.

I'm not sure what the bottom transistors are supposed to do. They seem to turn on in parallel with a LED in a way that simply wastes power.

edit: if it's a red/greed led, there are also easier ways to do this. Another problem is that you can never have both on at the same time (that may be a feature you want though)
 
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