opamp doubt

[ccatty]

hi friends,
im doin a line follower bot.
i hav 2 doubts.
my comparator output voltage when sensors blocked and unblocked are 3.7v and 2v.

these two are given as inputs to my 89c2051 controller.

the problem here is controller taking both 3.7v and 2v as logic1..

how to reduce the output voltage of comparator from 2v to 0?

or

how to make controller to take 2v as logic 0?

hope u l do clarify my doubt..

thnks

 

[kchriste]

Post a schematic of the comparator circuit and tell us which comparator you are using, etc.

 

[ccatty]

im using LM358 ( 8 pins, 2ports)

1 pin output
2 refernce voltage frm 10kpot
3 input from ldr
4 grnd
8vcc

 

[ccatty]

ive tried even LM324..that too giving me same problem

 

[kchriste]

There are two methods you can try:
1) Replace the LM358 with a LM393 and add a 10K resistor from pin 1 to Vcc (5V).

or

2) Put a 1K resistor between pins 1 and 4 on the LM358.

Method 1 is the best one. Method 2 may or may not work depending on how much current the LM358 is trying to sink.

QUESTION: Is the pin on the 89c2051 controller configured as an input?

 

[ccatty]

yes the two outputs(line foll) from LM324 is given as input to 2nd and 3rd pin of 89c2051

 

[Hero999]

WHy not use a microcontroller with a built-in comparator?

 

[colin mac]

Don't start 2 threads for the same subject.
The AT89C2051 has an on chip comparator.