Hello everyone. I took EE / circuits for a couple semesters in college out of high school 25+ years ago. So I know enough to get me in trouble. I do computer programming for a living now...
My little project is to listen to the audio on on an aircraft frequency. A number of microphone key clicks will turn on a relay to turn on landing lights at a small grass air strip.
I have written a program in Python for the Raspberry Pi 4B that I have attached a relay hat to.
Right now I am monitoring a button that I am pushing manually to count the number of 1/2 second long button presses. I am looking for 5 clicks in 10 seconds and turning on the relay. This is working nicely...
Here is the schematic for the button. The way I understand the drawing, the GPIO18 line is high (3.3 V) with the button open. When the button closes the 3.3 V goes to ground and the GPIO18 goes low. So low on / high off.
I want to replace that button with a circuit to take the 3.3 V to ground when the audio out comes on.
I found a circuit described on the internet to do this. Here is the updated circuit that I came up with.
Wil this work? What does the yellow highlighted line / arrow represent? Maybe a capacitor???
I copied the NPN transistors part numbers. Not sure that they are correct yet...
Any recommendations, suggestions, corrections or better ideas how to do this?