Tag: Dark sensor

An experiment with LDR and Arduino

It is a very simple experiment for Arduino amateurs, kids and beginners. It needs two LEDs, one LDR (Light Dependent Resistor), one tactile switch...

Amarino project- Arduino and Android based light sensor

With this project/application, you can make a light sensor dependent lamp. You can make a light sensor or dark sensor with this application. The light...

Experiments with 741- Operational amplifier

Description: This versatile 741 operational amplifier module can be used for making a dark detector using an LDR, a photo transistor and a photo...

Clap switch using 3 different modules

Description: In this clap switch we use three different modules given below. It is necessary to make these three modules in order to make...

Experiments with LM358

Description: LM358 is also one of the types of operational amplifier. LM358 consists of two independent, high-gain, frequency-compensated operational amplifiers designed to operate from a...

Monostable module

Description: In the monostable mode, the 555 works as a "one-shot" pulse generator.  Other applications of monostable mode include timers, pulse-width modulation (PWM), missing pulse detection,...

Light activated police siren using 555 timer and light dependent resistor(LDR)

Here's a simple light activated police siren using light dependent resistor and NE555 timer. Before you make this project, I would recommend you to...

Light dependent blinker using LDR and CD4093

Here's a simple experiment with LDR and CD4093. This is just a modification of a previous project "dark sensor using 2 transistors". In this...

Dark sensor using two transistors

This works same as the other dark detector circuit. When light is falling on LDR, its low resistance drives transistor Q1-BC547 into conduction. This...

Light operated switch

Light operated switch works with NE555 timer and light dependent resistor. It uses relay and toggle switch idea for operation.

Remote Operated Switch

When you press an infrared transmitter or normal TV remote control near TSOP1738 infrared sensor, the 555 timer configured in monostable mode gets triggered.

Basic RC circuit

For the circuit to work as light operated musical bell, we need to connect the SW1- switch to N/C terminal of relay. LDR has to be kept in a dark case.

FM transmitter and Dark sensor

A dark sensor can be converted to a simple FM transmitter using the following components. This FM transmitter is very sensitive and it has transmitting range of 30 meters.

Dark sensor using BC557

An automatic dark sensor can be made using a PNP transistor(BC557).

AM receiver from dark sensor

In this case, LDR has been replaced with capacitor C1-0.01uF and resistor R3-1K has been replaced with L1 & VC1. In place of a LED, a Piezo Diaphragm has been kept. We just need to add inductor, capacitor and a piezo diaphragm to convert a dark detector to an AM radio.

Object counter using LDR and calculator

To make an object counter we can use a simple dark detector circuit and a normal calculator. Pole and NO (Normally Open) terminals of a relay have to be connected to the two pins which are used to activate ‘=’ key of calculator. As we block the light falling on LDR, the calculator starts counting. For the calculator to work as a counter, we first need to press ‘1’ and ‘+’ keys.


A multivibrator is an electronic circuit used to implement a variety of simple two-state systems such as light emitting diodes, timers and flip-flops.

Remote Tester

Remote tester circuit also resembles the logic of a "dark sensor (using BC557)”. LDR has been replaced with IR sensor TSOP 1738. The circuit works as a remote tester. Pressing a remote control switch near the IR sensor, switches on the LED D2.

Voltage Divider Rule

A Voltage divider consists of two resistances R1 and R2 connected in series across a supply Voltage Vs. The supply Voltage is divided up between the two resistances to give an output Voltage Vo which is the Voltage across R2. This depends on the value of R2 relative to R1: If R2 is much smaller than R1, Vo is small (low, almost 0V) (because most of the Voltage is across R1) If R2 is about the same as R1, Vo is about half Vs (because the Voltage is shared about equally between R1 and R2) If R2 is much larger than R1, Vo is large (high, almost Vs) (because most of the Voltage is across R2)

Dark Sensor using 741

We can see how can we make heat sensor from dark sensor.