Week 6(How The Circuit Function And Connect)

Assalamualaikum..
For this week, I have to tell about the circuit function and connection.

The first important component in this block diagram is phototransistor.
The phototransistor is very sensitive device incorporating an amplifying circuit in the form.
 After that, buffer and differentiator (op-amp),
there is an optional extra stage to this project
and it’s also unaffected if light level change slowly
but show a sharp change in output when the level change rapidly. 

And the last part is switch and the load.
The function for the switch for tuning on and off the circuit.
When there is no voltage on the gate,
the channel exhibits its maximum conductance
and when there is no voltage on the gate, there is in effect no channel.
When the light is shining on the phototransistor,
the current flow’s result through resistor R1 and level control VR1 is series.
If the light level increase, the current through phototransistor TR1 increase.

The voltage across R1 and VR1 increase and the voltage at pin 2 falls.
The fall in voltage at the inverting input (-) of an op-amp produce a rise in voltage at the output.
The op-amp is connected as a comparator, with no negative feedback,
so it full open loop gain of around 200,000 comes into play.
The differentiator circuit diagram is a based on a second op-amp, IC2.
It takes its input from the trigger circuit. 
Input A is from the junction of the voltage divider resistor R2/R3,
which sits at half the supply voltage.
Input B comes from the output junction of the trigger op.amp,
IC1 and coupled to the inverter input (pin 2) of IC2 through C2.
The output of this op-amp is then used to drive TR2
and switch the load and l.e.d on or off.