How to Make a Dark Sensor Circuit

Are you looking to learn how to make a dark sensor? If so, then you’ve come to the right place! In this article, we’ll provide an easy-to-follow tutorial on how to make a dark sensor. With some simple materials and tools, you’ll be able to create your own dark sensor and use it to detect light in your environment. By the end of this article, you'll be able to make your own dark sensor and enjoy its many uses.  So if you’re ready to get started, let’s dive into how to make a dark sensor.

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.

The final circuit diagram and design can be seen above. We also thank to our sponsor JLCPCB (https://jlcpcb.com/RTA) for sponsoring us PCB for this project.

Thanks To JLCPCB.

$2 for 1-4 Layer PCBs.

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

We will provide an overview of the components needed, as well as step-by-step instructions on how to assemble and test the device. We will also discuss some ideas for possible components that can be used to create your own dark sensor. After reading this article, you should be able to confidently construct your own dark sensor. So, let’s get started !

To make this polarity protection circuit, we might need some electronics component. Those component lists have to been given below.

Component List :

1. PCB – made by JLCPCB

2. Transistor - BC 547

3. LED – 5mm

5. Resistor – 1 KΩ and 10 KΩ

6. LDR

7. Power Source – DC 12v

The Design of dark sensor circuit along with the PCB layout can be seen above. Power supply don’t included with the circuit. You can use any 12 battery for this project. 

The schematic of dark sensor circuit along with the PCB layout can be seen above.

• Maximum power dissipation is 200mW
• The maximum voltage at 0 lux is 200V
• The peak wavelength is 600nm
• Minimum resistance at 10lux is 1.8kΩ
• Maximum .resistance at 10lux is 4.5kΩ
• Typical resistance at100lux is 0.7kΩ
• Dark resistance after 1 sec is 0.03MΩ
• Dark resistance after 5 sec is 0.25MΩ

The advantages of LDR include the following -

• Sensitivity is High
• Simple & Small devices
• Easily used
• Inexpensive
• There is no union potential.
• The light-dark resistance ratio is high.
• Its connection is simple

The disadvantages of LDR include the following -

• Spectral response is narrow
• Hysteresis effect
• Temperature stability is low for the best materials
• In stable materials, it responses very slowly
• The use of LDR is limited where the light signal changes very quickly
• It is not so much a responsive device.
• It provides incorrect result once working temperature alters

There are some applications of LDR which are given below.

• The LDR is used in the infrared astronomy.
• The LDR is used in light failure alarm circuits and used in light meter.
• The LDR used in smoke detectors.
• It is used for automatic contrast and brightness control in television receivers.
• It is used in photosensitive relay
• It is used in optical coding.
• It is used in street light control circuits.
• It is used in camera light meters.
• It is used in the security alarm.
• It is used as a proximity switch.
• It is used in light activated control circuits.

To make this circuit we are using two resistors. One is 1 KΩ and the other one is 10 KΩ. We make a parallel connection is these two resistors. In this way, we got three terminals. One is common terminal and the other two terminals is empty terminal.

We connect this common terminal with one empty leg of LDR and the empty terminal of 1 KΩ resistor with Base leg of transistor. Then connect 10 KΩ resistor empty terminal with positive terminal of power source.

Now we need to connect LDR with the circuit. We connect LDR one terminal with collector leg of transistor and the other leg is connected with common leg of two resistors.

To make this automatic light circuit, we are using 3v (5mm) LED light. Connect this LED light positive leg with positive terminal of power supply and connect LED light negative leg with Emitter leg of transistor. 

Neat and perfect soldering is an important part for all kind of PCBs. Since soldering, you should remember that, there should not be any kind of short circuit connection. After soldering all legs, we cut-off the extra legs of all electronics component.

We also can use liquid PCB cleaner to clean the PCB board.

For power source we are using DC - 3.7v power supply. Connect positive terminal with LED positive leg and connect negative terminal with Collector leg of transistor.

Our circuit, is now completely ready for use. Now just plug-in the power supply and move LDR towards dark and light and enjoy the effect of this circuit.

Again thanks to JLCPCB for best quality PCBs.

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.

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