How to Make Sensitive Dark Sensor

In this project circuit, we are going to teach you making a sensitive dark sensor circuit. It is activated by a lack of light. It is a simple and powerful concept, which used transistor as a switch ON and OFF the light system automatically.

Light sensors are a type of photo detector that detect light. Different types of light sensors can be used to measure illuminance, respond to changes in the amount of light receive, or convert light to electricity.

To make this circuit, we are using LDR. LDR is a one type of photo resistor. Photo resistors, also known as light dependent resistor (LDR) are light sensitive device most often used to indicate the presence or absence of light, or to measure the light intensity.

LDR sensor is used for detecting the presence of surrounding light so that during the day time when sun is bright, the street light is switched off automatically. During the night time when there is no light, the LDR sends signal to microcontroller to turn on the street light.

The article is being published in collaboration with JLCPCB. They supply high quality PCBs at a very reasonable price. They also can provide SMT circuit assembly.

We thanks to our sponsor JLCPCB https://jlcpcb.com/RTA  for sponsoring us PCBs for this project circuit.

 For SMT Service, click here - https://cart.jlcpcb.com/quote?orderType=1&stencilLayer=2&stencilWidth=100&stencilLength=100&stencilCounts=5

Thanks To JLCPCB.

$2 for 1-4 Layer PCBs.

Get SMT Coupons - https://jlcpcb.com/RTA

To make this sensitive dark sensor circuit, we need some simple electronics component. You also can order assembled PCBs form JLCPCB. JLCPCB have its parts library. To check JLCPCB parts library, click here - https://jlcpcb.com/parts

All Component list have to been given below –

Component List –

1.        Relay – 12v
2.        Transistor – BC 547
3.        Resistor – 10 KΩ
4.        Diode – 1N 4007
5.        LDR
6.        LED – 12v
7.        PCB
8.        Power Source – DC 12v

BC547 is an NPN Bipolar Junction Transistor. And like all other transistors BC547 has three pins. If we count it’s leg form left side then, then called the emitter, collector, and base

BC547 transistor acts as a switch between the collector and emitter. If the base of the transistor is given enough current, this switch closes and the current flows from the collector to the emitter.

So a small current to the base pin of the transistor switches the large current between the collector and the emitter.

• This project can be implemented in applications like automatic switching on of lights when it becomes dark.
• This circuit can be part of a bigger circuit or project like home automation or home security system.

• This project can be implemented in applications like automatic switching on of lights when it becomes dark.
• This circuit can be part of a bigger circuit or project like home automation or home security system.

The schematics of PCBs can be seen above.

To make this amplifier circuit, we might need some electronics component. JLCPCB has its own parts library. JLCPCB has 200k+ in stock components, 24 hours rapid SMT assembly.

You can check SMT parts library here - https://jlcpcb.com/parts

To make this sensitive dark sensor circuit, 1^st we connect rectifier diode with the circuit. There are two coil terminal of a relay. We connect rectifier diode anode and cathode terminal with coil leg of relay.

The we connect 10 KΩ resistor with the circuit. Connect resistor one terminal with cathode leg of rectifier diode.

We utilize JLCPCB https://jlcpcb.com/RTA to printout our PCB

To glow light, now we need to connect DC-12v led light. Connect LED light positive leg with cathode leg of rectifier diode and LED light negative leg with anode leg of rectifier diode.

Now we need to connect transistor with the circuit. Connect BC-547 transistor “Base” leg with 10 KΩ resistor.

This time we connect transistor “Collector” leg with negative leg of LED light.

To control light, now we connect LDR with the circuit. We connect LDR one terminal with “Base” leg of transistor and it’s other terminal with “Emitter” leg of transistor.

Now we just need to connect power source with this sensor circuit. For power source, we are using DC – 12 volt power supply. We connect it’s negative cable with “Emitter” leg of transistor and power source positive cable with “cathode” leg of rectifier diode.

It’s the time to soldering and cut-off all extra leg of electronics component. Now we solder all component leg carefully and to make sure we need to check all of them for several times. We also remember that, there should not be any kind of short circuit connection. For perfect inquiry, we should use liquid PCB cleaner to wash PCBs.

Just power On DC-12v and made dark on LDR, then you will follow that, led light is glowing and make light on LDR, the LED light will be automatically off.

Thanks to JLCPCB for sponsor us such a quality PCB board.

If you complete design of your PCBs, then it is time to order PCBs. To order best quality PCBs, just visit JLCPCB and click on the “QUOTE NOW” button.

Since 2006, JLCPCB continuously driven to become more efficient and to reduce costs. They promise to offer customers the most economic PCBs forever. JLCPCB makes cheapest but top quality PCBs possibly because of scale effect, extremely high production efficiency and less manpower cost.

You can order minimum 5 pieces PCBs for only $2 costs.

To order PCBs, make your Gerber file. Then drag and drop the Gerber file on the following box.

Click on “Gerber Viewer” button you can check the PCBs design. Make sure everything is good, then choose color, quantity and order your PCBs at very reasonable prices.

If you are a new user, then you can order 10 pieces PCBs, costing only $2. To place your order click on “Save to Cart” button. Confirm your shipping address and shipping method.

To order your SMT PCBs, visit JLCPCB

1.    Drag and drop SMT PCBs file on site.

2.    Choose your PCBs color and quantity.

3.    To free SMT assembly for your PCB click on “SMT Assembly” button and then confirm.

4.    Add your Bom file and CPL file.

5.    Place your order click on “Save to Cart” button.

6.    Confirm your shipping address and shipping method.

7.    Pay your payment

8.    Wait for confirmation mail.

9.    For SMT Service, Click here.

JLCPCB supported all shipping method can be seen below.

Estimated Delivery Time

1. DHL International Express 3-5 business days
2. UPS Worldwide Saver 3-6 business days
3. S.F Express(Standard) 5-8 business days
4. S.F Express(Economy) 8-15 business days
5. Singapore EMS 8-15 business days
6. PostLink Registered Mail 15-20 business days
7. ePacket 15-25 business days
8. Registered Air Mail 15-20 business days

JLCPCB supported Payment method.

1.        PayPal
2.        Credit/Debit Care
3.        Prepaid wire transfer

To confirm your order, pay your payment. Then accept PayPal, Credit/Debit Card, prepaid Wire Transfer. To manufacture your PCBs, it’ll take about 2 days. DHL will be fastest shipping method to arrive your ordered PCBs at your location.

All PCBs were well packed and quality was really good.

Thanks to JLCPCB for best quality PCBs.