Hi Forum
Im going to make a rotary encoder for a project. I need roughly 1° resolution. Im going to lasercut a plate, and need some small sensors to read the holes in the plate. To avoyd a large diameter I need a sensor with a narrow "Beam" of detection. I can have a distance around 1 mm, from sensor to plate.
So I need a really narroww detection field.
Does anyone know of a sensor that fullfills this? I need a handfull, so price is also an issue.
Due to oil, dirt near the sensor i cannot use an infrared sensor. A hall sensor is not a good option either since i cannot have magnetic parts around the sensor. So im cutting the sensordisk in AISI 316 stainless.
Take a look at an air-variable capacitor. Turning the shaft on the capacitor changes the amount of penetration of the movable plate(s) into the stationary plate(s) -- and that in turn changes the effective capacitance.
That change in capacitance can be used to tune a high-frequency oscillator, and you can determine the relative location of the movable plates by measuring the oscillator frequency.
A round metal disk with a shaft positioned off-center, will generate a small, but measurable and continuous, variation in capacitance as the shaft rotates the disk near a stationary plate.
Something like that might work for you. And it's not hard to measure even very small changes in frequency given today's high speed digital electronics.
