This optical sensor, which is actually a simplified photometer, indicates in an instrument the intensity of light that is incident on an LDR. LDRs are very sensitive and if the LDR is placed in a tube with a lens, even the star brightness can be measured.
The experimental and didactic circuit presented uses few low cost components.
The LDR can even be obtained from an old television with automatic brightness control, but if purchased, will cost very little.
The instrument is a microammeter that can also be used for some old equipment that is not in use.
The power is made by only two batteries that will have great durability, since the consumption of the device is very low.
In figure 1 we have the complete diagram of the optical sensor.
The assembly can be made in a protoboard or a terminal strip, as shown in figure 2.
When assembling, observe the polarity of the batteries and the instrument, so that the needle does not tend to move to the wrong side.
The potentiometer adjusts the sensitivity of the circuit.
Material list
S1 – On-Off switch
B1 - 3 V - 2 AA or AAA batteries
M1 - Instrument of 100 uA at 1 mA
P1 - 47 k ohms - potentiometer
R1 - 1k ohms x 1/8 W - resistor - brown, black, red
LDR - round common LDR
Several:
Terminal strip, battery holder, mounting box, wires, solder, etc.
