Hi
I'm working on a tone decoder for my ultrasonic receiver. my goal is to detect input signal and verify whether its 40kHz. I'm using LM567chip for this. circuit is tuned for 40kHz and measured at pin 5.
my problem is circuit isn't working as it should be (according to data sheet)
please note in following diagrams C4 should be 0.02uF. I have incorrectly marked it as 0.001uF.
First attempt
This is the first circuit I tried
**broken link removed**
In this circuit LED does not light for the 40khz input signal. actually LED wont turn on what ever input it get.
Second attempt
Then my second attempt is disconnecting capacitor C1 from pin 1. then LED turned on dimly when there is no input and LED lights brightly when detecting 40kHz signal. this is the circuit
**broken link removed**
Third attempt
in my third attempt I connected 100k resistor from 5V to pin 1. after that LED is turned off when there is no 40khz input and LED turns on when detecting 40khz signal. but problem is now circuit responds to sounds other than 40khz signal.sounds like clapping and tapping sounds. when clapping LED blinks faintly.
here is the circuit **broken link removed**
Forth attempt
here I connected both C1 and R3 as in data sheet but result is same as attempt 1. LED doesn't turn on with or without signal
this is the circuit **broken link removed**
This is kind a funny. I cant figure out what the heck is wrong. first I thought LM567 was burned so I brought another but results are same.
can someone help me here? I'm pretty frustrated. ???
thank you
hi,
Found the last one.!
Built the circuit from the datasheet, the one I posted, I had to use a 22nF, thats 0.022uF thats the closest I have.
It works OK, thru a range of100mV thru 200mV, square and sine wave.
Nominal fo= 40.4KHz ........ BW ~ 38KHz to 44KHz
EDIT:
I am using a 20turn 10Kpot, if you are using a single pot you may find the adjustment too coarse.
hi,
Found the last one.!
Built the circuit from the datasheet, the one I posted, I had to use a 22nF, thats 0.022uF thats the closest I have.
It works OK, thru a range of100mV thru 200mV, square and sine wave.
Nominal fo= 40.4KHz ........ BW ~ 38KHz to 44KHz
EDIT:
I am using a 20turn 10Kpot, if you are using a single pot you may find the adjustment too coarse.
green wire is : well I use second half of LM358 as a comparator to the output of LM567. so green wire is from pin 8 of LM567 to inverting input of LM358.nothing to worry their i guess.
about 120k. well in datasheet it says adding 130k resistor between pin 1 and supply will set minimum threshold of sensitivity to 10mV. so 120k is for that.
If I connect 20nf to pin 1 and ground circuit stops responding
green wire is : well I use second half of LM358 as a comparator to the output of LM567. so green wire is from pin 8 of LM567 to inverting input of LM358.nothing to worry their i guess.
about 120k. well in datasheet it says adding 130k resistor between pin 1 and supply will set minimum threshold of sensitivity to 10mV. so 120k is for that.
If I connect 20nf to pin 1 and ground circuit stops responding