This device will tell a driver if his lights should be on and will wam him if the outside temperature is nearing zero by lighting a LED and sounding a buzzer9 VR1 adjusts sensitivity and LDR should be well protected..
This light-dependent sensor uses LDRs to detect the presence or absence of light. As long as the light source striking the LDRs remains constant, the alarm does not sound. ..
LDR1, a cadmium sulphide (CDS) photoresistive cell is used as the lower leg of a voltage divider between Vcc and ground. The timer terminals 2 and 6 are connected to the junction of the photocell and SENSITIVITY control Rl. The resistance of the photoresistive cell varies inversely as the light intensity; resistance is high when the illumination level is low; low in bright light. (The Radio Shack CDS cell 276-116 has a typically wide resistance range—about 3 megohms.....
As dusk begins to -fall, the sensor (a cadmium-sulfide light-dependent resistor or LDR) operates a small horn to provide an audible reminder that it's time to turn on your lights. To turn the circuit off—simply turn your headlights on and the noise stops. The base of Ql is fed through a voltage divider formed by R4, LDR1—a light-dependent resistor with an internal resistor of about 100 ohms under bright-light conditions and about 10 megohms in total.....
The circuit is activated by an LED/photoresistor isolator (Ul), which is a combination of a light-dependent resistor (LDR) and an LED in a single package. That device was chosen because of its high isolation (2000 V) characteristic, which is necessary because the strobe part of the circuit is directly connected to the ac line.The voltage divider is formed by R2, Ul`s internal resistance, and R3. When Ul`s internal LED is off, Ul`s internal LDR has a very high resistanceon.....
Meter Ml, a +/-50-uA zero-center D`Arsonval meter movement is driven by Ul, a TL081 FET op amp, through R3. The gain of Ul is set at 11 by Rl and R2, while capacitor 01 is used to restrict the bandwidth of Ul to 1.6 Hz. Power for the circuit is derived from a simple dual-polarity 12- V power supply (consisting of Tl, D3, D4, 02, and 03). A light-dependent resistor (LDR), R16 (which is a semiconductor element whose resistance decreases as it is exposed to increasing.....
The circuit can be used as a sensor that can trigger an alarm, without direct contact being made by the intruder. In this circuit, a visible or invisible light source radiates on the sensor, keeping the detection loop in what could essentially be called a normally closed condition. As long as the light source striking R5 remains uninterrupted, the switch remains closed. But if an intruder passes between the light source and the sensor, the circuit goes from closed to.....
This circuit has the CMOS IC doing double-duty performance. The first two inverters operate as a digital audio oscillator; the third operates as a low-gain linear audio amplifier. As the intensity of the light falling on photoresistor LDRl increases the oscillator's frequency increases; similarly, the illumination falling on photoresistor LDR2 determines the volume level from the loudspeaker: ..
The circuit"s threshold is set by resistor R2. When the intensity of the light falling on the LDR is lowered, resistance of ..
A cadmium sulfide photocell (LDR1, which is a light-dependent resistor) is connected to the base and collector of an npn transistor, Ql. When light hits LDR1, the internal resistance goes from a very high (dark) value to a low (light) value, supplying base current to Ql, turning it on. The voltage across Rl produces a bias that turns Q2 on, which in turn, supplies the positive voltage to Ul at pin 8 (the positive-supply input) and pin 4 (the reset input), to operate the.....
Integrated-circuit Ul—an LF351 or 741 op amp—is used as a comparator to control the light. Resistors R2 and R3 provide a reference voltage of about 2.5 volts at pin 3 of Ul. When daylight falls on light-dependent resistor LDR1, its resistance is low: about 1000 ohms. In darkness, the LDR's resistance rises to about 1 megohm. Since Rl is 100,000 ohms, and the LDR in daylight is 1000 ohms, the voltage ratio is 100 to 1; the voltage drop across the LDR is less.....
The change in ambient light triggers the alarm by changing resistance of LDRl and LDR2. ..
This ring detector, utilizing a neon-LDR (light dependent resistor) optocoupler, simplifies inter ..
The circuit is built around an LM339 quad comparator, Ul, which forms the basis of a Schmitt trigger, timer circuit, and a window comparator. One comparator within the LM339 (pins 1, 7, 6), plus LDR1, R4, R5, R6 and R8, is used as a Schmitt trigger. The timer circuit (which receives its input from the Schmitt trigger) consists of R9, RIO, Rll, R13. The last two-fourth's of Ul (pins 8, 9, 10, 11, 13 and 14) are wired as a window comparator. The two inputs to the window.....
The circuit shown here is used to switch on a lamp when the tele- phone rings, if the ambient light is insufficient. The circuit uses only two ICs and it can be implemented very easily. A light dependent resistance (LDR), with about 5 kilo-ohms resistance in the ambient light and greather than 100 kilo-ohms in darkness, is at the heart of the circuit. The circuit is fully isolated from the phone lines and it draws current only when the phone rings. The circuit provides.....
This kit is the most basic, practical circuit to build using an LDR to turn on a relay. The two transistors connected as a Darlington pair give the circuit enough sensitivity, while the trimpot give sensitivity adjustment. The switching point of the relay is dependent on the supply voltage and temperature. This circuit is satisfactory if the changes in light level to be detected are large and the transition is quick - for example, a person walking past a doorway......
Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front.....
The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable multivibrator at a frequency of about 1kHz. When no light falls on the LDR, the transistor is pulled high by the variable resistor. Hence the transistor is OFF and the reset pin of the 555 is pulled low. Due the this the 555 is reset. When light falls on the LDR, its resistance decreases and pulls the base of the.....
The device serves to quickly establish the status of an indicative power cells. I built it for his children, so they can determine the degree of self-discharge batteries in a variety of toys. WAS tester designed to test the fast primary (zinc, alcaline) Cell. Contains simple voltage converter and level indicator. The tester is powered from tested cell. Supply current is depend of cell voltage at 1.5 V and is approx. 200 mA. For high efficiency voltage converting Must be a.....
I Specifically Designed this circuit to charge 2 Batteries for my Digital Cameras, but it can be modified to charge 3, 4, 5 or more cell. However, It will Not Work with only One Cell as that voltage is too low for even this LDR Discharge Regulator. If you decide to Always charge 4 or more batteries, the REG1117A could be replaced with an LM317. But with only Two cell, this will not work. It is Recommended to set the discharge, Down to 1.1 volts per cell at a rate of 1/10.....
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