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Author Topic: 2 leds one comparator output  (Read 203 times)
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Voidugu
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« on: January 27, 2013, 01:46:19 am »
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I would like to know if it is possible to control two leds separately using a single comparator output. ie above a certain voltage a  green led is on and a red is off, below a certain voltage, the green led is off and the red is on.

Thank you in advance
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Runaway Pancake
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« Reply #1 on: January 27, 2013, 11:14:16 am »
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Yes, if the comparator has an open collector output 1.

> > >  1 Like an LM339, for example.
« Last Edit: January 27, 2013, 11:22:40 am by Runaway Pancake » Logged
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Hippynerd
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« Reply #2 on: January 27, 2013, 11:25:07 am »
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I am totally unfamiliar with a comparator, but i am familir with charlieplexing, you could charlieplex 2 LEDs, and reverse polarity to switch LEDs.
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Grumpy_Mike
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« Reply #3 on: January 27, 2013, 02:09:50 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: Voidugu on January 27, 2013, 01:46:19 am
I would like to know if it is possible to control two leds separately using a single comparator output. ie above a certain voltage a  green led is on and a red is off, below a certain voltage, the green led is off and the red is on.
Where is this variable voltage coming from?
If it is the analogWrite command be aware that this does not output a variable voltage but a pulse width modulated signal. You need a filter to make that an analogue voltage.
http://www.thebox.myzen.co.uk/Tutorial/PWM.html
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