This electronic music maker uses an astable oscillator circuit that is controlled by a photocell. The light falling ..
Although theIR region is free from radio interference, it is subject to interference from incandescent lamps, fluorescent lamps, stray reflections, and other sources. A simple way to overcome that problem is to create a carrier by chopping the IR radiation at a rate of 100 kHz. The audio then modulates the carrier by modulating the chopping rate. A receiver then detects the IR beam as a 100-kHz FM signal. ..
This is a complete telephone bell replacement circuit with minimum external components with on-chip diode bridge and transient protection..
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...
When the doorbell switch is pressed, the two monostable stages are activated in sequence, applying bias to a pair of voltage-controlled resistor stages. These then modulate the outputs from a pair of tone generators. The resulting signals are fed to an audio amplifier, ..
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. ..
An audio signal applied to VI is passed through the operational amplifier 741, U2. After being amplified, the output signal V2 is sampled and applied to a negative voltage doubler / rectifier circuit composed of diodes CRI and CR2, with the capacitor C1. The resulting negative voltage is used as a control voltage which is applied to the door] 2N5485 FET Q1. Capacitor C2 and resistor R2 form a filter for smoothing the voltage rectified audio control. The lFET is connected.....
The circuit keeps the courtesy light on for 30 seconds after you close the door. The lead from the door switch is removed and connected to the 555 circuit. The 555 is arranged in a monostable mode, and is triggered by the door switches. The output drives Ql, which is connected across the interior light switch. The interior light is turned on for 30 seconds after the door is opened. If the door(s) are held open for longer than 30 seconds, it will not reset until after.....
High quality, noise free, wireless FM transmitter/receiver operates over standard power lines. Complete system is suitable for high-quality transmission of speech or music, and will operate from any ac outlet anywhere on a one-acre home site. Frequency response is 20-20, 000 Hz and THD is under Transmission distance along a power line is at least adequate to include all outlets in and around a suburban home and yard..
It is often desirable for a single doorbell to be operated by two buttons, for instance, one at the front door and the other at the back door. The additional button, S2 in series with the break contact of relay Rel, is connected in parallel with the original bell-push, SI. When S2 is pressed, the bell voltage is rectified by D1 and smoothed by CI. After a time, t = R{R2C2, the direct voltage across C2 has risen to a level here T1 switches on. Relay Rel is then energized.....
A simple FM wireless microphone uses a single BC183C transistor as an audio amplifier. A 2N3565 can be substituted. ..
Use standard rf wiring precautions. The best speech clarity is obtained by using an electret microphone. ..
This dark-activated relay switch can be used to turn on walkway or other outdoor lighting at dusk. By using alternate connections to A and B, increasing illumination, ..
The monitor senses an ajar door and, if the situation isn"t corrected within 20 seconds, sounds a beeping alarm. The circuit is controlled by a magnetic reed switch and magnet on the door. With the door closed, the switch is closed and the alarm is disarmed. Opening the door opens switch, Cl starts charging up through Rl. Approximately 20 seconds later, the voltage at pin 9 is high enough to tum on the oscillator formed from C, D, R2, R3, and C2. ..
The single-chip, burglar -alarm circuit shown uses a dual 556 timer, draws 10 mA of standby current, and generates a pulsing alarm signal that conserves battery energy. Once activated, the alarm wilLremain on, independent of the subsequent state of any of the sensors. The sensors support both deferred and immediate-action modes. You can attach this circuit to your car"s internal lighting circuitry using a single wire and a relay. To arm this circuit, you open your car.....
The control circuit operates to double from a positive supply, which, when turned on the power of the first door. and goes off when the first drain as shown in FIG. This circuit integrates the LM123, a three-terminal positive regulator and a dc dc + converter, whose output power drains and gates of GaAsFET-power relay in a power amplifier. The controller output drives a three-terminal DC + DC converter - which exit through an N-channel lFET properly so as to pull the base.....
Most car door switches are simply single-pole switches, with one side grounded. When the door is opened the switch grounds the other line thus completing the light circuit. In a car where the negative terminal of the battery is connected to the chassis, the negative wire of the unit (emitter of Q2) is connected to chassis the positive wire (case of 2N3055) is connected to the wire going to the switch. In a car having a positive ground system this connection sequence is.....
The purpose of this circuit is to control the water temperature in a hot-water heating system. What it does is to lower the boiler temperature as the outside air temperature increases. The op amp is used as a comparator. Thermistor TH2 and R2 form a voltage divider that supplies a reference voltage to the op-amp"s inverting input. Thermistor TH2 is placed outdoors, and the values of TH2 and R2 should be chosen so that when the outside temperature is 25 °F, the.....
This high-performance video-camera link transmits signals from your video camera to your VCR, or from your VCR to TVs throughout your home. The first stage of the rf chain is a crystal-controlled oscillator, Q1, with a frequency of 60 to 65 MHz, which is one-eighth of the final output frequency. The oscillator produces a signal of about +6 dBm (4 mW) that drives three stages of frequency doublers. The combined action of those doublers multiplies the input frequency by.....
A small neon lamp is triggered into conduction by the telephone's ringing voltage, passes just enough current to activate the LED in optocoupler Ul, which in turn triggers the 6-A Triac that controls 12—a 117-Vac lamp or bell. (Capacitor Cl is necessary only when the circuit is used to drive a bell.) The lamp will flash off-and-on at the ringing rate, which is normally around 20 Hz. ..
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