When SI (sensor) is closed, power is applied to U2, a dual timer. After a time determined by C2, CI is ene..
Pulses from the distributor points are passed through a current limiting resistor, rectified, and clipped at 4 volts. Via Q1 and the diode pump, a dc voltage proportional to engine rpm is presented to RV1; the sharp transfer characteristic of a CMOS gate, assisted by feedback, is used to enable the oscillator formed by the remaining half of the 4011..
The meltdown is a magnet held to a small stand by ice. A reed switch is below the magnet..
The ramp voltage from the low frequency oscillator 1C1 modulates IC2 thereby producing a rising and falling tone like the siren ..
When the light beam that falls in the CDS photocell is interrupted, transistor (EN3904) conducts thereby triggering SCR1 (CI06) and activating alarm bell. SI resets the SCR. The alarm bell should be a self-interrupting electromechanical type...
This is a cross-sectional diagram of a flex switch. They can be used as pushbutton or even position sensors. This schematic diagram shows an oscillator, which is used as an alarm sounder,..
The base of Ql is connected to the car`s ignition circuit; the easiest point to make that connection is at the ignition switch fuse in the car`s fuse panel. Also, one side of the piezoelectric buzzer is connected to the instrument-panel light fuse; when the headlights or parking lights are on, the instrument panel is lit, too. When the headlights are off, no current reaches the buzzer. Therefore, nothing happens. What happens when the headlights arc on depends on the.....
Two SCRs are used with two sensor loops. One loop uses series switches, the other loop parallel switches. When a switch actuation occurs, the SCR triggers...
IC1 generates a pulse that modulates the 1000-Hz tone generated by IC2...
False alarms produced by semiconductor failure are impossible with this burglar-alarm circuit equipped with relays. What"s more, the circuit is virtually immune to false triggering. With a standby current of less than 0.1 mA, the circuit offers all the features an alarm needs: entry and exit delays, a timed alarm period, and automatic reset after an intrusion. One CMOS CD4093B quad NAND gate, IC1, supplies both logic and analog timing functions with the aid of.....
The tone generated by a 555 oscillator can be turned on (activated) by heat or light. That causes Ql to conduct transistor W2 (TIP 3055)...
When liquid level reaches both probes, alarm is turned on..
Four parallel switches are used to monitor four positions. When a closure occurs on any switch, SCR1 triggers, which sounds the alarm...
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. ..
The circuit can be tuned to respond to signals between 50 MHz and 500 GHz. The economy model is shown in Fig. 1, and the deluxe model is shown in Fig. 2.The first op amp in each circuit functions as a current-to-voltage converter. In the economy model IClb buffers the output to drive the piezo buzzer. The deluxe model functions in a similar manner except that IClb is configured as a 20 buffer amplifier to drive the LM386. In both circuits Cl functions as a "transmission.....
Using a few bipolar transistors, this circuit acts as a flood alarm. When liquid touches the probes, leakage current biases Ql,..
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.....
This circuit simulates the sound of an American police siren. IC2 is wired as a low frequency astable that has a cycling period of about 6 seconds. The slowly varying ramp waveform on Cl is fed to pnp emitter follower Ql, and is then used to frequency modulate alarm generator IC1 via R6. IC1 has a natural center frequency of about 800Hz...
Using a PA41 from Apex Microtechnology, this monolithic amplifier is capable of 350-V operation ..
This strobe gives a visual indication of a sensor input. The input signal causes Ul, a light dependent resistor, to chaijge CI..
Operational Amplifiers
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