encodermicrocontroller
I am doing an 8th semester project but I need to use an IR transmitter and receiver to find the wheel direction of car. I would like 8051 assembly level code to find wheel direction. I am using two IR transmitters and receivers to find direction. I am mounting these two IR modules to get following combination of output.
clockwise direction
LH-HH-HL-LH
Anti clockwise direction
LH-HL-HH-LH
If you are measuring 0V across your resistor, then it looks like your LED is blown (open circuit)
V / R = I, so 0V * 220 = 0mA. This means there must be a high impedance in series with the resistor (i.e. open circuit LED)
There are two things you should do.
Firstly, implement a little bit of hysterisis. Currently, it look like you're using 200 as the threshold in both the rising and falling direction. What you'll always get with analogue sensors is a bit of noise. This means that, even during a rising edge, you might actually see a tiny falling edge sometimes. You might even see it cross your threshold up, then down, then up again!
So, when the signal is rising, use 200 as your threshold. And when the signal is falling, use something like 150 as a threshold.
Secondly, you could use both the rising and falling edges to calculate your speed. That way you can have twice the update rate.
Best Answer
This isn't the usual rotary encoder pattern, but it should still work. See this wikipedia section for the normal gray-code implementation.
Basically, you will need to:
The disadvantage of your setup is that it takes two transmitters, probably has a more complicated pattern drawn, and there's no way to identify if the encoder has gone 2 steps instead of 1. Additionally, only one bit changes with the gray code count, so the comparison routine is easier and not a look-up table.