Here is the circuit diagram of an ultra sensitive intruder alarm. The shadow of an intruder passing few meters nearby the circuit is enough to trigger the alarm. Here IC2 uA 741 is wired as a sensitive comparator, whose set point is set by R6 &R7. The....

This is an automatic light dimmer circuit. You do not need to dim the lights by yourself. It is so very convenient, because we use the LDR to detect external....

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Most of the time a charged lead-acid battery and a power inverter would be used to ensure a smoothly organised holiday where ideally the missus and the children cheerfully use their electric and electronic gear! With rechargeable lead-acid batteries it`s....

This circuit is intended for children fun, and can be installed on bicycles, battery powered cars and motorcycles, but also on models and various games and toys. With SW1 positioned as shown in the circuit diagram, the typical dual-tone sound of Police or....

This simple circuit is build around a CMOS IC 4060 to obtain the required timing. During day time the LDR has low resistance and keeps the pin 12 of the IC1 high, preventing the IC1 from oscillating. When it is dark the LDR resistance becomes high and the....

This simple robot, which responds to light and avoids obstacles, can be built without using a microcontroller, programmer or PC. The only special` component in the circuit is a window discriminator (a fancy version of a window comparator). Resistors R1 and....

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This circuit is intended for children fun, and can be installed on bicycles, battery powered cars and motorcycles, but also on models and various games and toys. With SW1 positioned as shown in the circuit diagram, the typical dual-tone sound of Police or....

he following circuit shows a Photo Alarm Electronic Circuit. This circuit based on the 555 Timer IC.  Features: LDR ( photoresistive cell),  ....

This is an actual reverse engineered circuit diagram of the one transistor circuit most commonly used to drive Permanent Magnet DC motors in childrens` toys. This type of circuit almost always uses the 625mW version of the ubiquitous 8050 or 8550 transistor.....

The left hand side transistor T1 is rigged as a voltage comparator using a resistive network. The resistor at the upper arm is the LDR and the lower arm resistor is the preset which is used to set the threshold values or levels. T2 is arranged as an....

The following circuit shows about Sensor Circuit Diagram Of Automatic Room Lights. This circuit based on the CD4017 IC. . Features: uses two LDRs, ....

This photoelectric smoke detector circuit uses one LED and 2 LDRs to detect the smoke and sound an alarm. The LM1801 IC is the best choice for this circuit....

A Light Dependent Resistor (LDR) to create a simple childrens bedroom nightlight which turns on automatically when it gets dark and turns off when it gets light. An LDR`s resistance changes depending upon the amount of light hitting the sensor. For the LDR....

This circuit is intended for children fun, and is suitable to be installed on bicycles, battery powered cars and motorcycles, but also in models and other games. With SW1 positioned as shown in the circuit diagram it reproduces the typical dual tone sound of....

A simple fire alarm circuit based on a LDR and lamp pair for sensing the fire. The alarm works by sensing the smoke produced during fire. The circuit produces an audible alarm when the fire breaks out with smoke. When there is no smoke the light from the....

Here is a project of a simple dark detector LED circuit. In the previous topic we have discussed a light activated LED circuit. By simply changing the positions of the resistors and LDR we have converted the circuit in a dark detector LED or dark activated....

This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question, or to move a piece etc. In this view it`s a modern substitute for the old sandglass. Useful also for....

Here is a project of a simple automatic night lamp circuit or dark activated 230V lamp circuit, which will automatically activate an AC lamp / bulb when sun set or if the circuit will receive no light. The circuit is very easy to build using no more than....

This versatile 741 operational amplifier module can be used for making a dark detector using an LDR, a photo transistor and a photo diode. The amplifier has been configured in inverting mode. It compares the change in voltage at pin 2 with the reference....

A replication of Afrotechmods laser tripwire circuit. Using a simple laser pointer, IRF244 MOSFET ( most NPN transistors would do the job), a couple of resistors and one LDR..

It relies on the smoke that is produced in the event of a fire and passes between a bulb and an LDR, the amount of light falling on the LDR decreases. This type of circuit is called optical smoke detector. Do not use it as a home smoke detector it`s jus for....

I n this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises). 2. When light falling on LDR2 is obstructed. 3. When door switches are opened or a wire is broken. 4.....

Two-Tone Siren Circuit Schematic Using One IC Circuit This circuit is intended for children fun, and can be installed on bicycles, battery powered cars and motorcycles, but also on models and various games and toys. With SW1 pos....

When the light falls on the LDR, it becomes low ohmic. The voltage at the junction of LDR/R2 charges the C2 via the R1 slowly. After about 10 seconds, the capacitor voltage reaches the input threshold of U1. Then U1 generates a square wave signal with a....

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This circuit uses a very simple approach to detecting smoke in the air. Quite simply, it uses a bulb as a light source, and an LDR (Light Dependent Resistor) as a light detector. As fire smoke comes between the bulb and LDR, the resistance of the LDR....

This circuit is a toy to encourage young children to count. Power is turned on by switch S1, then S2 is closed. This makes nine LEDs flash slowly. S2 is then opened and the LEDs go out. Pressing push-button PB1 turns on a random number of LEDs - briefly -....

Automatic dark detector senses darkness. As the light level decreases and LDR meets the maximum threshold resistance, the circuit automatically switches on the LED D1. A light detector senses light. As the light level increases and LDR meets the lowest....

Normally, Thereminworks by detecting hand proximity using capacitive coupling method. A Theremin circuit shown in the schematic diagram below use different method to control the pitch. The oscillator of this tone generator, both the volume and frequency are....

The Theramidi is a new musical device, based on the Theremin, which produces a MIDI signal relative to the movement of objects to or away from it. The MIDI output is controlled by the intensity of light falling onto two Light Dependent Resistors (LDRs). One....