hi,
The values of the voltages you posted.
Show that pin 7 of the 555 has no voltage on it, this is what you would expect if the IR detector was not receiving a signal from the transmitter.
Under this condition of no input to pin7, the output pin3 will always be high after power up. This is a flaw in the circuit design.
The voltage you have on pin3 [output] of the 555 is driving the buzzer.
If you measured D3 while its soldered to the pcb, the resistance measurement is not reliable.
The only function of D3 is to slightly forward bias D4, so that low level signals can be rectified.
As I explained the circuit works OK on a simulator, with the exception of the power up latching the 555 pin3 output high.
This can be cleared by placing the emitter diode close to the receiver diode so that D4 can drive the inputs of the 3 comparators.
Do you follow.?
The values of the voltages you posted.
Code:
+Vs - 9,6v
A - 0,48v
B - 0
C - 0
D - 0
E - 0,05v
Show that pin 7 of the 555 has no voltage on it, this is what you would expect if the IR detector was not receiving a signal from the transmitter.
Under this condition of no input to pin7, the output pin3 will always be high after power up. This is a flaw in the circuit design.
The voltage you have on pin3 [output] of the 555 is driving the buzzer.
If you measured D3 while its soldered to the pcb, the resistance measurement is not reliable.
The only function of D3 is to slightly forward bias D4, so that low level signals can be rectified.
As I explained the circuit works OK on a simulator, with the exception of the power up latching the 555 pin3 output high.
This can be cleared by placing the emitter diode close to the receiver diode so that D4 can drive the inputs of the 3 comparators.
Do you follow.?