Looking for IR LDR

Hi Group.
Im into making an angle detection system with a arduino. It will work with an ir led iluminating some ir photo recievers. With an pin blocking the light I can calculate the position of the pin.
Hereby making a cheap anmgle detection system.
I need a IR resistor that I can put on my adc to determine the amount of IR hitting the sensor. But intil now the ones i have found not suitable. I think they are made for IR communication and has a steap slope (allmost on/of).
Anyone know of a IR reciever that has a more linear curve? Just like a ofd fashioened LDR.


What you’re looking for is an IR phototransistor.

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If there is also visible light you might need a filter. An IR phototransistor or photodiode is usually optimized for IR but not completely insensitive to other wavelengths.


QSB34CGR onsemi | Sensors, Transducers | DigiKey

The linearity of the IR LED could be a problem. It's sort-off a cone-shape with lobes.

I would like to see the mechanical setup, for better understanding of the problem.

Here is a quick sketch of the setup
Let me explain.
• The base is fixed, and houses 2 LED receivers, so I can read the intensity of the IR light hitting them.
• The base also has a pin bearing that holds the arm I want to measure the angle to. This pin has 2 purposes.

  1. It acts as a bearing for the swing motion of the arm.
  2. It casts a shadow from the IR transmitter, so the receivers will never get full exposure (at the same time) from the transmitter.
    • By reading the intensity of the light the light ratio of the 2 sensors should give me an idea of the arm angle.
    It might need a little fiddling and LUT correction to get it accurate, but that is OK. I basically just need to keep the arm close to neutral angle. The whole assembly cam be wrapped away from direct sunlight, or I can make readings with the emitter off, to compensate for ambient light levels.

Does it make sense?
Instead of having IR receivers with an on/off characteristics I would like to have some that could give me a range of light values, so I can better calculate the arm position. Ideally a LDR resistor with a restince of 1K-1M ohm would be ideally. I could just adc the values easy without need for any instrument amplifier. But I cannot really figure ouw what component to use,


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