Electronics

Minggu, 04 November 2012

Wiper Interval Timer Kit

Windshield Wiper Interval Timer Kit
Up to 3 different time intervals (2 - 10 - 15 seconds) can be selected for the windshield wipers of your car. It can also be used for automatic slide projection.

Specifications:

relays on PCB: 2 inverters
power supply: 12 - 15V DC
PCB dimensions: 3.2" x 2.2"

Indicator Kit

Frost Indicator Kit
Drive more safely in freezing weather. This kit uses a flashing LED to indicate a road temperature close to freezing point ; below that point the LED is on continuously. A reliable temperature sensor with mounting stud is included.

Specifications:

power supply: 10 - 15V DC / 25mA
PCB dimensions: 2.2" x 1.7"

Alarm Simulator

Car Alarm Simulator Kit
Want to deter your local thief without spending hundreds on a car security alarm? LED with 'realistic-appearing' flash sequence simulates active car alarm system.

Ingeniously simple circuit can tell if your car is running or not by detecting the voltage difference when the car is on and off. This occurs because when your car is running the Alternator puts a out a voltage a little bit higher than when the car is off.

Specifications:

Activates automatically when the engine is turned off.
Easy to install, just two wires to connect
Adjustable sensitivity to control on and off state.
Low current consumption: 12mA max. (12V only)
Comes complete with pre-wired LED-holder and two warning labels
Dimensions: 2.3" x 1.8"

head light indicator

This head light indicator may be set for one or two functions. To indicate that the head lights (or the side lights) should be switched off after switching off the ignition contact (battery protection). Or to indicate that the head lights should be on once ignition contact is switched on (obligatory in some countries).

Specifications:

continuously repeated alarm tone for lights ON (may be disabled)
repeated alarm tone for lights OUT
only 3 wires are required for hook-up
supply voltage: 12V DC
PCB dimensions: 1.9" x 2.2"

Rabu, 24 Oktober 2012

Germanium diodes

Germanium diodes are a type that has been in use since the early days of radio and although they have been largely superceded by silicon signal diodes and integrated circuits, they may still be found as signal diodes in older radio circuits, where they are used in such applications as radio signal detectors (demodulators) where the voltages involved in demodulating AM radio signals are likely to be small, less than 1Vpp (0.5Vpk). Germanium diodes will conduct at a forward voltage of only about 0.15V, but a silicon diode will not start to conduct until a forward voltage (positive on the anode) of 0.6V is reached.

The demodulator that recovers the audio signal from the amplitude modulated (AM) radio waves can use a germanium diode as a rectifier to remove the unwanted half of the AM signal. It works in a similar way to a rectifier diode in a simple power supply; it passes one half of the incoming radio signal and blocks the other half. The main differences being that the frequency of operation is much higher, also the voltages used in a demodulator are tiny by comparison to a mains (line) power supply.

Silicon rectifier

Silicon rectifier diodes, are used in many applications from high voltage, high current power supplies, where they rectify the incoming mains (line) voltage and must pass all of the current required by whatever circuit they are supplying; this may be several tens of Amperes or more.

Carrying such currents requires a large junction area so that the forward resistance of the diode is kept as low as possible. Even so the diode is likely to get quite warm. The black resin case helps dissipate the heat.

The resistance to current in the reverse direction (when the diode is "off") must be high, and the insulation offered by the depletion layer between the P and N layers extremely good to avoid the possibility of "reverse breakdown", where the insulation of the diode fails due to the high reverse voltage across the junction.

Silicon diodes are made in many different forms with widely differing parameters. They vary in current carrying ability from milli-amps to tens of amps, some will have reverse breakdown voltages of thousands of volts; others use their junction capacitance to act as tuning devices in radio and TV tuners. Look in suppliers lists to see the many types available.

Light-Emitting Diode (LED) circuit

Usually, circuit is made with some basic parts such as capacitors and resistors. Those basic parts are then built into some several combination that structure building blocks for other circuits.

Some people who have enough experiences might not find any difficulty in designing electronic circuit. First, you need to know well about the characteristics and behavior of either intermediate or advanced components of electronic circuit. Sometimes, you can find sample circuits that will help you get more information in using the parts. Some parts that usually contain this information are including semiconductors such as diodes, transistors, as well as op-amps.

Second, you should also learn more about some basic circuits used in many kinds of electronic devices. You will also get this information easily from any basic electronics text. For example, you can have more practices in modifying a Light-Emitting Diode (LED) circuit.

Simple Ways To Understand The Filter Capacitors In Electronic Circuits

Executive SummaryBy Jestine Yong

You could see mica capacitors, ceramic capacitors, tantalum capacitors, aluminum electrolytic capacitors, paper capacitors and etc. Electronic Field - Act as filter to remove ripple in power supplies;

- As inter stage signal coupling capacitors- A capacitor will not pass DC, but an AC signal will go through;

- Tuning resonant circuits, oscillator circuits;

In today's article I'm going to talks about capacitor act as filter to remove ripple from power supplies. Usually, the filter includes one or more capacitors. The capacitors are then placed between the DC line and ground. This unwanted noise signal can cause problems in electronic circuit. If all capacitors checked okay I would then move on to another circuit. Why not one filter capacitor is enough for each DC line voltage? The answer is that the big filter capacitors (large value) at the secondary side of power supplies is to smooth the DC and remove unwanted lower frequency noise.