Precise, adjustable control of beats per minute from a largo of 18 to a frenzied, high presto of 500, These beats are produced acoustically through a speaker. A light flashes at the same rate. When SW1 is closed, CI begins to charge through Rl and R2. Cl will eventually reach a voltage at which the emitter of unijunction transistor is switched on, "dumping" the energy stored in Cl into an 8 ohm speaker. To produce a distinct "plop", brief pulses across T2 secondary drive.....
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 sensor is based on the selective absorption of hydrocarbons by an n-type metal-oxide surface. The heater in the device serves to burn off the hydrocarbons once smoke or gas is no longer present in the immediate area; hence, the device is reuseable. When initially turned on, a 15 minute warm-up period is required to reach equilibrium (V, = 0.6 V) in a hydrocarbon-free environment. When gas or smoke is introduced near the sensor, VA will quickly rise (rate and final.....
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.....
This circuit holds on the internal light for approximately one minute after the car doors are closed. When the door contacts open, a + VE pulse is applied to the base of Tl. This transistor turns on, turning off T2 and charging the 10-llF capacitor. T3 turns on, holding on the internal light. ..
A 555 timer IC, operating in the one-shot mode, is triggered by light striking photoresistors. These normally have a resistance of several megohms but, in the presence of light, that resistance drops to several hundred ohms, permitting current from the six-volt source to flow in the circuit. The R-C combination shown gives an on-time of about two minutes. Photoresistors PC3 and PC4 are mounted at heatlight-height. When headlights illuminate the photoresistor, the timer.....
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..
This ultra wide range timer uses a 555 timer base, two 4017Bs and a 4020B that act as frequency dividers that can be switched in and out...
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. ..
Using a few bipolar transistors, this circuit acts as a flood alarm. When liquid touches the probes, leakage current biases Ql,..
Operational Amplifiers
Computer Systems
Oscilloscopes
Transmitters & Receivers
Sensors & Detectors
ANSI Standards
Low Frequency Amplifiers
Power Amplifiers
Number Systems
Regulated Power Supplies
Analogue Filters
Digital Gates
