Many people have a phobia of darkness, so to help them in such a situation, we have explained a simple circuit. The street light will automatically turn on in the form of LED or bulb coupled with relay, it is well enough to see the object close. This circuit is very easy to work and also the battery power consumed by the circuit is very low due to the very few components used in the circuit. The entire circuit is based on IC CA3140 which is basically an operational amplifier that can connect the PMOS voltage transistors to the high voltage bipolar transistor on a particular chip. LDR (light dependent resistance) whose resistance is based on the amount of light that decreases in it along with some more components.
Circuit diagram of street light switch circuit breaker using relays and LDR:
Components used in this circuit:
• IC
• CA3140-1
• Resistance
• R1 (100k) - 1
• R2 (560E) - 1
• R3 (1K) - 1
• R4, R5 (100K) - 2
• VR1 (100K) - 1
• C1 (10uF) - 1
• LDR - 1
• T1 (BC548) - 1
Components Description:
LDR: LDR is a device whose sensitivity depends on the intensity of the light that falls on it. When the force of light falling on LDR increases the resistance of LDR decreases, whereas if the force of light falls on LDR it is increased decreased resistance. In dark time or when there is no light, the LDR resistance is in the range of mega ohms, while in the presence of light or in diminishing brightness by a few hundred ohms.
LDR Test- Before mounting any component in the circuit it is good practice to check whether a component is working properly or not so that you can avoid time consuming troubleshooting. For the LDR test set the multimeter range in resistance measurement. After you put the lids on the legs of LDR (like LDR have no polarity so you can connect any cap with the leg). Measure the resistance of LDR in the light or brightness, the resistance must be low. Now cover LDR correctly so that no light beam falls, measure again the resistance that must be high. If you got the same result it means that LDR is good.