Recption detection circuit for a half duplex transceiver

Thread Starter

alimash

Joined Oct 12, 2016
62
Hello friends
I have a half duplex transceiver meaning i can only transmit or receive signal at a time.
My objectif is to use the sound signal coming out of the headphone jack of the device to detect if there is reception (meaning thrre is someone who is talking) by making a circuit that give high output "1" if someone is talking and low output "0" if no one is talking.
Obvisouly i don't want to detect noise.
Is it feasable?
 

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Thread Starter

alimash

Joined Oct 12, 2016
62
It does actually.
I tried to use the analogue pins of an adruino but there was many error reading.
Do you think that it is only a matter of adjustements ?
 

djsfantasi

Joined Apr 11, 2010
6,196
It does actually.
I tried to use the analogue pins of an adruino but there was many error reading.
Do you think that it is only a matter of adjustements ?
What specific error messages are you seeing on the Arduinos?

You do realize that the ground of the transceiver must be connected to the ground of the Arduino... Otherwise the analog input on the Arduino won’t see anything meaningful.

Also, the headphone common may NOT be the same as the transceiver ground.

Finally, you’ll need to test for a range of voltage presented in the input to account for analog noise. That is instead of checking for 0V for no input, you should check for anything under 0.05V. Or something like that. I picked that number for an example. Similarly, you need to check for an upper threshold to check for sound. Like (another made-up number), greater than 0.50V.

You can use a comparator to compare the difference between headphone common and the speaker wire. If the voltage is really small, you can amplify it as well.

Also, you’re looking at audio. The signal is AC and depending on when you read it, you could get a range of voltages. Hence, you might want to tack on an envelope detector OR process the signal in software.

As to the latter suggestion, I’d code the analog reads to take a rolling average over some finite number of samples. I have done this with 10 samples.

I’ve given you many ideas, because I’m not sure if what you’re trying to do beyond your basic problem description. As noted herein, there are many considerations.
 
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