LDR Pot | Making | Matching | Plotting

[ In the quest of making programmable Lab ]
First use case: controllable vRef for Adc
todo: test it in signal chain

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All of this can be made using arduino, without any extra components that I have used.
Pairing it with something like TLC5940 (16x4096-step pwm) could give more than a few bits of resolution.
Since LDRs are slow, fast pwm hopefully will not affect the signal chain :D
LEDs also have a second option, - the ability to produce photons without ever blinking, if required :)

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Enjoy the videos!

Make "Uber Potentiometer" by using 2x LEDs & LDRs

A---|\/\/\/\/|---TAP ---|\/\/\/\/|---B

Move not only the TAP between A & B, but change the resistance of the POT itself !

Easy Variable Gain OpAmp control?


Arduino sketch file

x-arduino - 2.10 kB - 04/26/2017 at 08:30


  • 1 × Arduino Uno Mega or any other mcu
  • 1 × 10k resistor
  • 21480 × LDR
  • 1 × 74HC4067 Electronic Components / Misc. Electronic Components
  • 1 × LED -Single colour or RGB (will have to check, maybe common cathode)

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  • 1
    Step 1

    All that is needed is Arduino and unused digital pins. Having a bigger board like Mega could accommodate more LDRs. All that is needed is digitalWrite(). The same board can also drive PWM pins to drive LEDs that drive LDRs.. clear? good!

    I wanted to have fun and used 74HC4067, 16-1 Analog Mux from Nexperia,
    so the instructions part, of switching on/off 5vdc will be based around muxing, the rest is pure arduino, use anything that shines the light, use port expanders, go bonkers !

    Yes, plugging Analog Mux Z pin(common input or output) to 5vdc and driving LDRs :D (it can do Digital multiplexing and demultiplexing too)

  • 2
    Step 2

    Connect and play, please bear with me while I'm Fritzing, in the mean time here is some video candy

    No numbers can ever replace a nice plot!

  • 3
    Step 3

    Use data sheet to find out the peak spectral response and tune your LEDs to that wavelength.

    Having unbranded and undocumented LDRs makes the whole thing much more interesting. Might write a sketch for doing just that, finding LDR spectral peak response using RGB LED etc

View all 4 instructions

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