i finished my NE555 circuit and created some pcbs. After a few attempts i could get the circuit working, and tested it successfully. I placed my circuit between a 12V 1.5Hz square wave signal and a 12V LED strip. Everything worked fine, the circuit delayed the on-time of my led by a few hundred milliseconds. Then I went for a week on vacation and when i came to test my circuit a second time, and nothing worked... (The circuit was laying on my desk and no one was at home) The output voltage was not delayed any more and the output voltage was synchronous to the input voltage.
Luckily, i had ordered 10 pcbs and had parts to solder a few more... I did so, and tested my circuit with my lab bench power supply and measured every pin/trace with my oscilloscope. Everything was fine and with my R1 potentiometer I could change the delay time of the output signal.
I decided to connect the new circuit between the +12V square wave and my led strip and now nothing worked any more!? But in difference to the first pcb, the output voltage of this one stays at 0 volt for the whole time. Back on my lab bench power supply and my oscilloscope i could reproduce this problem. The circuit did not work any more.
The strange thing now is, that the capacitors voltage changes if i change the resistance of the potentiometer. If i set R1 to 0Ohm, the Capacitor i charged up to 12V. If i set R1 to 5k Ohm, the capacitor only charges up to something like 8V!? The higher I set R1, the lower gets the Capacitor voltage? If is test the same combination of capacitor and potentiometer on my breadboard, everything works just fine and the capacitor gets charged up to 12v every time, just the the charging time varies when i set the resistance higher or lower (How it should be).
Maybe someone can tell me what is going on and what i did wrong? I am really freaking out because even with my oscilloscope i can't find the root of the problem.
I attached my scheme and my pcb design ;)