Getting signal only when I unplug Digital Pin 5 on TTL LC-type Oscillator?


I am trying to re-create the TTL LC-type Oscillator/Theremin as Capacitative Sensing Device using breadboard and Arduino Uno R3. The code is from:

When I run the code, the Arduino uploads it fine, but I cannot get a signal reading on the Serial Monitor unless I unplug Digital Pin 5. I have attached two pics here showing how I hooked it up. I have tried swapping Arduino boards, but the same happened so I am thinking I messed up somewhere on the breadboard side. I am following the schematic diagram from the website above - I am totally new at this, so any help is greatly appreciated. Thank you!

I am totally new at this

So why did you not read the how to use the forum sticky. Those pictures are way too big to be useful. You should resize them so they are no more than 1000 pixels wide. Click on one and see for yourself.

Some points:- 1) Never connect a speaker directly to an output pin. The load it presents to the pins is too high and you will end up damaging the arduino. Put at least a 125R series resistor in the circuit, it will not be as loud but it will be safe.

2) Your construction is all spread out, this is important when you are dealing with high frequencies like you are here. The circuit should be built as compact as possible. I am not even sure it this will work as a bread board due to the stray capacitance between the tracks of the bread board.

3) Those capacitors look like they are the wrong value. C3 and C4 look like they are 10nF not 10pF. One nF is 1000pF, I am not sure about C1 either.

4) By removing the digital input you are letting the input float, that means it just picks up interference, not a good idea, see:-