PIC16F877a chip - IR interfacing: need help

[tamer1221]

IR interfacing

I want to signal condition a photodiode line sensor output to a digital input.

Although I am using the PIC16F877a chip,

I have designed, built and tested a bank of 8 IR Transmitter/ Photodiodes pairs.
They all return 1.2 to 4.2 volts depending on a light or dark surface below the sensors.

I ultimately want an 8-bit digital pattern where the sensors might react like this when travelling over a black line.

00011000
00001000
00001100
00000100
meaning the robot is drifting off center.

Seems like I have several options:
Lets say I use Port B as an input port.

1. If I just run the sensor inputs to the port, it would seem that I would get what I want; zeros or ones.

2. Could I send the 1.2-4.2 volt signal through some kind of chip like an inverter to "clean up" the signal and only produce 0 or 1? I know an opamp could do this, but that seems like overkill.

3. How about an LED/resistor voltage divider to drop the 1.2 down to 0.7 to make sure I get a zero into the chip at low voltage??

4. I could use ADC, but it seems inefficient to convert the voltage into an 8 bit number just to turn it back into a one or zero.

So what would you do???

 

[herlambang]

IR interfacing

You can ue single op-amp as comparator it's commonly to use..
you can set voltage reference at 4V and you can use non inverting comfiguration.

it's the logic of comparator

if the input voltage < 4V
output =0
else 1

you can change the reference voltage depends on your need.

hope it can help
regard