i have seen plenty of schematics.Thanks but will i have a result with this cause i use squeare wave 25%duty cycle frequency not ac input.So the capacitor will stay charger when the input is low for the 75% to active my transistor?probably i have to use a big capacitor to achive this.What do you think?

 

Yes you have right i mean unmodulated IR beam.I put only a frequency in the emmiter and i am trying to detect this frequency from the receiver.

 

hi,
In that case use a 567 tone decoder ic after the IR detector.
Please post a simple diagram.

http://www.njsas.org/projects/bat_de...pulel_sch.html

I know this is for ultrasound but will give you an idea...

Attached Files

LM567.pdf (176.2 KB, 7 views)

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Hi ariakovo,

I understand how datasheets can be confusing, because other applications than the one you want may also be presented. In the case of the 567, go to its page 8.
You will see a circuit called AC test circuit and application information on the right side that gives the formula for calculating the frequency you need. In this case, it is:
1/(1.1*R1*C1)

I have attached a part of a schematic from a circuit I built with actual values. I don't recall at the moment what its frequency was. On that circuit, the components to adjust the frequency are labeled C4, R7, and R8. That is, the RC filter attached to pins CT and RT. YOu will need to calculate appropriate values for the frequency you decide to use. Good luck. John

Attached Images

TONE DECTECTOR.PNG (15.7 KB, 12 views)

 

Ok i am sending you the diagram.Maybe i will make a high pass filter because i don't have a lot of sapce in there.I am waitin the components the next week for testing.Also the filter invert the output.If i solve this problem we will talk about this later maybe i will find a solution but i want this first.Thanks for you time

untitled.GIF

 

Thanks for the tips.You said that there is a RC filter.Can i use the lm567 like a filter and like a demodulator?For example if i put one other frequency how will respond.If i can't it's ok.I understant how to calculate the frequency.Thanks

 

It will respond only to the frequency to which it is tuned (don't forget it has a finite bandwidth). A sufficiently different frequency will not cause a change in its output state. In fact, its name "tone decoder" described that function. A series of 567s tuned to the different telephone tone frequencies could tell you which keys had been pressed. John

 

Thanks a lot!!

 

The envelope detector is a good circuit to start with. It will detect the presence or absence of any signal over a wide bandwidth. To be more selective there needs to be something that responds to frequency. Googling "phase locked loop" will also result in numerous hits. Check out the number two hit
http://www.uoguelph.ca/~antoon/gadgets/pll/pll.html