Hi,
I'm trying to build a circuit that detects audio pulses. The idea is for one circuit to transmit a binary sequence by turning on and off an oscillator connected to a speaker (so 1 is transmitting, 0 is silent), with a second circuit detecting the pulses and changing them back to 1s and 0s.
For the receiving circuit I'm using an LM567 tone detector, and I'm essentially just using a circuit I **broken link removed**.
The transmitting circuit is using an oscillator (at the moment just a signal generator) to give out a 10kHz sine wave. I'd like to be able to switch this on and off fairly rapidly, to give a reasonable data rate.
According to the datasheet for the LM567 (https://www.electro-tech-online.com/custompdfs/2011/05/LM567.pdf) it can turn on and off at f0/20 ('Fastest ON-OFF Cycling Rate'; where f0 is the frequency to be detected) - so for a frequency of 10kHz (which it is detecting) it should be able to detect pulses at 500Hz (ie. the time between the 10kHz signal switching on and back off again can be as low as 2ms)
At low frequencies, the circuit works as expected - with the pulses at 3Hz or slower it turns on when a pulse is sent and off when it isn't. But any faster than about 3-5Hz and it stops detecting them.
Connecting a scope to the input and output, it seems that it takes a long time to detect that there is a 10kHz signal there. This is why it stops recognizing the pulses - much faster than about 3Hz and it doesn't have time to detect that the 10kHz signal is there before it turns off again.
The datasheet, however, says that it should be able to work considerably faster.
Can anyone see anything obvious I'm getting wrong? I'm not a *complete* beginner, but I'm no expert and haven't used the LM567 before.
Also - How fast a response would you expect? Is my 3Hz detection typical for a 10kHz signal, or should I be getting something better?
Thanks for the help!
I'm trying to build a circuit that detects audio pulses. The idea is for one circuit to transmit a binary sequence by turning on and off an oscillator connected to a speaker (so 1 is transmitting, 0 is silent), with a second circuit detecting the pulses and changing them back to 1s and 0s.
For the receiving circuit I'm using an LM567 tone detector, and I'm essentially just using a circuit I **broken link removed**.
The transmitting circuit is using an oscillator (at the moment just a signal generator) to give out a 10kHz sine wave. I'd like to be able to switch this on and off fairly rapidly, to give a reasonable data rate.
According to the datasheet for the LM567 (https://www.electro-tech-online.com/custompdfs/2011/05/LM567.pdf) it can turn on and off at f0/20 ('Fastest ON-OFF Cycling Rate'; where f0 is the frequency to be detected) - so for a frequency of 10kHz (which it is detecting) it should be able to detect pulses at 500Hz (ie. the time between the 10kHz signal switching on and back off again can be as low as 2ms)
At low frequencies, the circuit works as expected - with the pulses at 3Hz or slower it turns on when a pulse is sent and off when it isn't. But any faster than about 3-5Hz and it stops detecting them.
Connecting a scope to the input and output, it seems that it takes a long time to detect that there is a 10kHz signal there. This is why it stops recognizing the pulses - much faster than about 3Hz and it doesn't have time to detect that the 10kHz signal is there before it turns off again.
The datasheet, however, says that it should be able to work considerably faster.
Can anyone see anything obvious I'm getting wrong? I'm not a *complete* beginner, but I'm no expert and haven't used the LM567 before.
Also - How fast a response would you expect? Is my 3Hz detection typical for a 10kHz signal, or should I be getting something better?
Thanks for the help!
