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Reverse Color Organ

Jon Jerpbak

Jul 24, 2015
3
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Jul 24, 2015
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Using a light organ (Velleman MK114), I want a light to turn off to the music rather than turning on. This means the normal state of the light is on. I've tried using a NOT gate but the voltage coming out of the color organ is quite varied and the NOT gate is just on/off. I do not have access to an oscilloscope.
I'm looking for a device or circuit that will adjust the output voltage depending on the input voltage.
As an example:
Assume that the color organ out put voltage is anywhere between 0v and 9v.
If the input of this 'new' circuit is 0v, i want the output to be 9v.
If the input is 3v, i want the output to be 6v.
if the input is 9v, i want the output to be 0v.
I just need to be pointed in the right direction.
Thanks
 

AnalogKid

Jun 10, 2015
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Jun 10, 2015
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2,884
Please post the Velleman schematic. In the mean time, it sounds like you are asking about an analog inverter. Not the same as a digital not gate because in your case there is no implied reference to invert things about. An inverting opamp with an offset of Vcc/2 or 4.5 V will do what you describe. Whether or not it will work in your application is a different thing.

aka
 

Jon Jerpbak

Jul 24, 2015
3
Joined
Jul 24, 2015
Messages
3
Thanks for your answer, I'll start looking into your suggestions. I have attached the schematic
 

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Alec_t

Jul 7, 2015
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....and disconnect pin 4 of the opto coupler from ground.
 
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