I want to ask why the pulses that come from the output of the comparator do not increase the counter ( Timer 1 ) value, meanwhile, using a single pulse generator increase it ,although they are all high and low pulses !! I really don't know why !! can anyone please help me

 

Hello,

Basicaly the inout is almost floating and pulled high.

Have a look at the change I made:

Bertus

 

actually I didn't get it

the circuit is working ,you can see this from the led when connected to the output of the op-amp comparator

ِAlso when I use the oscilloscope is see the pulses ( high and low ), and everything looks good until I feed it to the T1 pin ,the counter doesn't count anything !!

 

 

Did you set the P3.5 for input in the software?

When I first saw your thread, I got my 8051 book out and there is sort of step by step procedure for setting the timer for counting.

 

Yes for sure

counter is working well when I put a single pulse generator

but when I replace it by the circuit shown the counter doesn't work

 

A 741 generally cannot swing withing a volt or two of the power supply rail. This is probably your problem.

 

so, what should I use instead

 

A comparator will work better in this application. Ensure you include a pullup resistor on the output if it has an open collector output.

Oh, and get rid of the Q1, R1 and R4. You don't need them.

 

Could you please give me the comparator number, I've tried 6 commercially available comparators in Proteus library ,but unfortunately nothing works

I used Q1 ,R1 and R4 intentionally for a certain purpose

 

Could you please give me the comparator number, I've tried 6 commercially available comparators in Proteus library ,but unfortunately nothing works

I used Q1 ,R1 and R4 intentionally for a certain purpose

Some of the other guys here will hopefully give you a number. I haven't used a comparator in years. LM311 comes to mind, but the input voltage range may or may not be good enough for your application.

BTW, I just noticed your Q1 and R4 is badly configured. There is no place for the base or emitter current to go. You should remove R4 (replace it with a short). Then, apply your 10K resistor between the emitter and ground. I think your circuit, as is, may work then.

 

I removed R4 ,but nothing new, counter still not working !!

I used a 555 timer ,triggered by the comparator output ,and now I can see the timer pin counting the pulses ,is that a good solution ?