Troubleshooting Part II

The original circuit is originally design using a Variable Resistor VR1, 47k value. The VR1 function is to varied the sensitivity of the circuit. Specifically, VR1 will adjust the voltage at the non-inverting (+) input to make it equal to the steady inverting (-) input after the sound is absence.

The lower value of VR1, the more sensitivity the circuit will be. Means that, even a little sound detected can trigger the circuit. So, we decided to make the circuit is less sensitive. Sir Saiful suggested to us to use the value of VR1 in the range of 60k to 70k. We head down to Jalan Pasar again to search for that particular value of VR1, but we didnt manage to find one. We bought a 100k instead. 

We changed the value of VR1 from 47k to 100k in the circuit. The result is as expected. Using a 100k VR1, the sensitivity become less. 

The 47k value of VR1

The circuit VR1 is change to 100k value, can be seen in the bottom of the circuit, far left.

The bright lights have been dimmed after the VR1 is varied.

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