The first amplifier circuit is a bird phone. In this circuit, the electret mike (MIC1) is mounted in the neck of a large plastic funnel. The amplifier, built around an MC34119 (which is available from D.C. Electronics, P.O. Box 3203, Scottsdale, AZ 85271-3203; Tel. 800-467-7736, and elsewhere), is then placed outside of the funnel with the pickup facing a nearby bird feeder. The output of the amplifier is then connected to a 16- speaker. The amplifier`s voltage gain is.....
A gas sensor (TGS823 from Allegro Electronics, Cornwall Bridge, CT 06754) conducts in the presence of explosive gases. U5 is a voltage-to- frequency converter that produces a frequency proportional to the sensor conductance. The output frequency ranges from 100 IIz in clean air to 8 kHz in a contaminated atmosphere. The dc voltage from the sensor also drives bar graph LED U7 and comparators U4-b and U4-c to sense present caution and danger levels. ..
An optoelectronics device is used to couple a digital (TTL) signal to another system. The photodiode in the optocoupler drives an LM311 set up to produce a TTL compatible output...
Glitch has been a universal slang expression among electronics people for an unwanted transient condition. In D/A converters, th..
A GC Electronics P/N J4-815 transducer is used to receive 40-kHz acoustic remote-control signals...
This switching arrangement is the type of arrangement used in both domestic and industrial environments to allow a light or other ac-operated device to be controlled..
This circuit comes from U.S. Patent 3, 778,800, granted to BRK Electronics in Aurora, IL. The circuit provides a smoke detector with an alarm for both smoke and low batteries. The R6/R7 voltage divider monitors the battery and will turn Q2 and Ql off when the battery voltage falls too low. The smoke-detector chamber will also cut Ql off when it senses smoke. ..
Fixed-value capacitors are disc ceramics. CI, C4, C5, C6, and C8 are NPO ceramic or polystyrene. C2 is a 25-pF ceramic trimmer and C3 is a 15- pF miniature air variable capacitor. The resistors are -W carbon film or composition. The RF chokes are miniature Mouser Electronics No. 43LR103 units. For LI, use 32 turns of #28 enamel wire on an Amidon Assoc. T50-6 (yellow) toroid. L2 has 25 turns of #28 enamel wire on an Amidon Ft-37-61 ferrite toroid. Schematic diagram of the.....
The unit consists of a sensor, timer, and electric water pump. The sensor is embedded in the soil, and when dry, the electronics operate the water pump for a preset time. The circuit is composed of a level sensitive Schmitt trigger, variable time monostable, and output driver. When the resistance across the probe increases beyond a set value (ie, the soil dries), the Schmitt is triggered..
Reprinted with permission from Radio-Electronics Magazine, February 1989. Copyright Gernsback Publications, Inc. 1989. Antennas that are much shorter than 1/. wavelength present a very small and highly relative impedance that is dependent on the received frequency. It is difficult to match impedances over a decade of frequency coverage. Instead, input stage Ql is an FET source-follower. A high-impedance input successfully bridges antenna characteristics at any frequency. ..
These two circuits are SSB generators. One uses a crystal filter by KVG Electronics at 9 MHz, the other uses a 455-kHz mecha..
The proliferation of industrial and computerized equipment containing programmable memory has increased the need for reliable recording media. The magnetic tape medium is presently one of the most widely used methods. The primary component of any magnetic recording mechanism is the write mechanism. The concept of the write generator is very basic. The digital input causes both a change in the output amplitude, as well as a change in frequency. ..
Door open alarms are used chiefly in automotive, industrial, and appliance applications. This type of circuit can sense the opening of a refrigerator door. When the door opens, a triac could be activated to control the inside light. The figure shows a door position alarm. When the door is opened, an LED turns on and the piezo alarm sounds for approximately 5 seconds. This circuit uses a TL3019 Hall-effect device for the door sensor. This normally open switch is located in.....
This very special mains-operated dimmer for domestic or industrial lights is not available in proprietary form: it ena..
Circuit for applying a dc-coupled FM or PPM to a 555 configured as an oscillator. IC-1 - Motorola MC-1374P. IC-2 - National LH0002C. L1, L2 - Mouser Electronics #421IF200. C1. C2 - Silver mica, 300 pF. All 0.1 uF cap., ceramic disc, 16V. C3 - 100 uF, 10 V, electrolytic ADJUSTMENT: Adjust R1 for minimum carrier; signal from function generator should generate 500 mVpp at pin 8 of IC-2 (suppressed carrier double sideband). Adjust R2 and function generator level-to achieve.....
Industrial applications sometimes require that power be only briefly applied to a load following the closure of a switch, such as a microswitch or foot switch. The load could be a heating element for use in sealing plastic bags, a de motor that is indexed or stepped with each application of power, or a de solenoid which is to be energized for a brief time-for example, a staple gun. ..
The sensor is an RC oscillator in which, a water-absorbent plastic film is the insulator in the capacitive element. The capacitance of the film increases with the amount of water it absorbs from the air, and thus reduces the oscillation frequency. A frequency counter produces a digital output that represents the change inirequency and hence the change in relative humidity. The sensor can be used to measure humidity in the atmosphere, in the soil, and in industrial.....
Such jobs as jewel cutting and polishing require the workers to switch on/ off two electrical appliances one after another repeatedly for two different services on the same workpiece. This is cumbersome as they need to fully concentrate on delicate handwork on precious jewels. Switching in such situations cannot be done by hand, and doing it by foot using ordinary switches is too tedious...
Another very simple audio preamp to build. all parts should be available at your very local electronics shop...
I don`t know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider), movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because at my local electronics store they are over $4 Cdn. Instead, an oscillator made up of two sections of a 4011 NAND gate is employed. This chip is very inexpensive and extremely common...
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
