Help with getting LMC567 to detect tone

[kevin360]

lmc567

I'm hoping someone can shed some light on why this isn't working for me. At first I tried using two LMC567 chips that were both using the same value resistors and capacitors so they'd be at the same frequency (~2kHz). I then fed the output (pin 5) of the first LMC567 to the input (pin 3) of the second LMC567 but it didn't change the output at all. Since it wasn't working I thought that maybe the bandwidth was too narrow and the variance in the R & C components made the frequencies they operated at too different, so it wouldn't detect the tone. So the next test was to take one LMC567 and feed it's output (pin 5) to it's input (pin 3) - still no change at the output.

Right now the values I'm using are Rt=110k, Ct=3.3nF, C1=4.7uF, C2=4.7uF. If anyone wants me to draw up a circuit to see what it looks like I can do that, just let me know.

Thanks for any help you can give.

 

[Audioguru]

lmc567 circuits

The output of an LMC567 is not a tone. It is a transistor with an output DC voltage near ground when its input is fed a tone of the correct amplitude and correct frequency.

I think its output needs a pullup resistor so that it is at the supply voltage when it does not detect the correct tone.

EDIT: The output is pin8, not pin5.

 

[bongkk]

tone decoder lmc567

Try this circuit. It has worked reliably for me. The Vcc for a 567 is quite critical, make sure it is 8Volts. Also, don't leave out the Vcc decoupling capacitor.

Added after 33 minutes:

Try this circuit. It has worked reliably for me. The Vcc for a 567 is quite critical, make sure it is 8Volts. Also, don't leave out the Vcc decoupling capacitor.
Oops.. I forget to upload the image. here it is.

 

[FvM]

lmc567 circuit

EDIT: The output is pin8, not pin5.

Apart from using a 567 as tone decoder, it can also work as an oscillator. In this case pin 5 is the square wave output.

Basically, you should be able to connect the square wave output to the input of another 567. But, the signal must be
AC coupled and possibly needs some attentuation.

There are also useful applications, where the 567 output is feed back to the input. I remember, that I used it for an AC operated
single chip optical reflective sensor. However, if you understand it's phase detector operation, you would know, that pin 5
hasn't the right phase to produce an output signal.