Liquid Crystal Light Valve Circuit

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kevinmold
 
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Liquid Crystal Light Valve Circuit

Post by kevinmold »

Hey yall, I'm new around here and I am starting a project that I need some guidance with. I've been browsing the forums for quite some time and know there are some very smart and experienced folks here!

I am wondering what may be the best way to use a Trinket MO to switch a liquid crystal light valve from transparent to dark at selectable rates. Ideally I would like to use a knob to vary the rate at which it is "strobing" from 30fps to 60fps.

Here is the light valve I will be using:
https://www.adafruit.com/product/3330#tutorials

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adafruit_support_bill
 
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Re: Liquid Crystal Light Valve Circuit

Post by adafruit_support_bill »

That should be a fairly straightforward project. You can attach your knob to a 10K ohm pot with the wiper connected to one of the analog pins on your processor.

The Trinket M0 is a 3.3v processor, so the GPIO pins will not be able to drive the LCD quite all the way to maximum density. If you need maximum density, you can use an external transistor to switch the higher voltage (up to 5v). Or you could just use a 5v processor like the ItsyBitsy 32U4: https://www.adafruit.com/product/3677

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kevinmold
 
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Re: Liquid Crystal Light Valve Circuit

Post by kevinmold »

Thank you for your reply!
I have seen on someone else's project using these light valves, they needed a resistor to "drain" the voltage to 0 to become fully transparent. Is the itsbitsy able to output a square wave at this rate to allow for full transparency then to full density?

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adafruit_support_bill
 
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Re: Liquid Crystal Light Valve Circuit

Post by adafruit_support_bill »

That project was probably using some sort of 'open emitter' type of circuit. These can actively drive the output HIGH but need a pulldown resistor to pull it back to zero.

The GPIO pins on the Atmega 32U4 have a 'totem-pole' type push-pull output that will actively drive the output HIGH or LOW. So no pulldown is needed.

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