Wiring circuit

Showing posts with label explanation. Show all posts

Saturday, October 25, 2014

Power Monitor Non Contact Diagram Circuit

Here is a simple non-contact AC power monitor for home appliances and laboratory equipment that should remain continuously switched-on. A fuse failure or power breakdown in the equipment going unnoticed may cause irreparable loss. The monitor sounds an alarm on detecting power failure to the equipment. The circuit is built around CMOS IC CD4011 utilising only a few components. NAND gates N1 and N2 of the IC are wired as an oscillator that drives a piezobuzzer directly. Resistors R2 and R3 and capacitor C2 are the oscillator components. The amplifier comprising transistors T1 and T2 disables the oscillator when mains power is available. In the standby mode, the base of T1 picks up 50Hz mains hum during the positive half cycles of AC and T1 conducts.

Contactless

This provides base current to T2 and it also conducts, pulling the collector to ground potential. As the collectors of T1 and T2 are connected to pin 2 of NAND gate N1 of the oscillator, the oscillator gets disabled when the transistors conduct. Capacitor C1 prevents rise of the collector voltage of T2 again during the negative half cycles. When the power fails, the electrical field around the equipment’s wiring ceases and T1 and T2 turn off. Capacitor C1 starts charging via R1 and preset VR and when it gets sufficiently charged, the oscillator is enabled and the piezobuzzer produces a shrill tone. Resistor R1 protects T2 from short circuit if VR is adjusted to zero resistance.

The circuit can be easily assembled on a perforated/breadboard. Use a small plastic case to enclose the circuit and a telescopic antenna as aerial. A 9V battery can be used to power the circuit. Since the circuit draws only a few microamperes current in the standby mode, the battery will last several months. After assembling the circuit, take the aerial near the mains cable and adjust VR until the alarm stops to indicate the standby mode. The circuit can be placed on the equipment to be monitored close to the mains cable

Saturday, October 18, 2014

MJ2955 for IC 78xx Boosting Regulator Current Diagram Circuit

Source :: http://www.zen22142.zen.co.uk/Circuits/Power/boosti.htm

IC 78xx series of voltage regulators are available with different current outputs, you can boost the available current output with this circuit. A power transistor is used to supply extra current to the load the regulator, maintaining a constant voltage. Currents up to 650mA will flow through the regulator, above this value and the power transistor will start to conduct, supplying the extra current to the load. This should be on an adequate heat sink as it is likely to get rather hot. Suppose you use a 12v regulator, 7812. The input voltage should be a few volts higher to allow for voltage drops. Assume 20 volts. Lets also assume that the load will draw 5amps. The power dissipation in the transistor will be Vce * Ic or (20-12)*8=40watt. It may keep you warm in the Winter, but you will need a large heatsink with good thermal dissipation. If you want to Boost the output current with a negative regulator, such as the 79xx series, then the circuit is similar, but an NPN type power transistor is used instead.

555 timer Electronic roulette wheel Diagram Circuit

Using a simple voltage controlled oscillator a 555 timer IC and 4017 counter/divider IC can be designed a very wonderful electronic roulette wheel game.
This electronic circuit is a simple version of an electronic roulette game and is based on the 4017 IC which is a 10 stage decade counter/divider. It is driven by another versatile IC 555 configured as a voltage controlled oscillator (VCO).
The 555 timer is connected as an astable multivibrator . When the S1 switch is pressed, the capacitor C3 gets charged, also at this point of time a constant stable clock is fed to the 4017 IC and the LEDs at its outputs light up in a cyclic manner producing a revolving effect. Adjusting the VR1 (variable resistor ) the speed of revolving effect can be varied .
When the S1 switch is released, the main supply is cut-OFF, C3 discharges and forces the freely running astable to gradually stretch and slow down the time period of its output pulses so that eventually the oscillations stop within a stipulated time. In response to these dying pulses the “rotation” of the LEDs connected to the output of IC 4017 also slow down gradually and stops to select a random score marked on the board.

Depending on how long the S1 switch remains depressed score will always be selected in random order .
This electronic roulette wheel game must be powered from a simple 9 volt DC power supply

Monday, October 13, 2014

Signal Amplifier For TV explanation Charecteristics and circuit

This is a small, broad band, signal amplifier which covers the frequencies from 40 to 900 MHz. These frequencies include TV in VHF and UHF and also the radio broadcasting frequencies in the 88 - 108 MHz FM band.
It is connected between the antenna and the input of your receiver and boosts the signals by up to 20 dB, thus making it possible to receive even the weakest signals.


Dimensions (4,3cm x 5,4cm)

Technical Specifications -Characteristics

Frequency response: 40 - 900 MHz
Gain: . 20 dB
Maximum output level: 90 uV
Input - output impedance: 75 ohm

How it Works

The circuit is built around a single transistor a UHF low signal device, the BFW 92. This transistor can operate in frequencies as high as 1.6 GHz, and has a gain of 23 dB. The signal from the antenna is applied to the input of the circuit and through C5 is fed to the base of the transistor. It is amplified and from the collector of the BFW 92 through C2 and C1 is taken to the input of the radio or TV receiver.
The circuit operates off a small 9 V battery which, because of the very low power consumption of the circuit, is going to last for a very long time.

Construction

First of all let us consider a few basics in building electronic circuits on a printed circuit board. The board is made of a thin insulating material clad with a thin layer of conductive copper that is shaped in such a way as to form the necessary conductors between the various components of the circuit. The use of a properly designed printed circuit board is very desirable as it speeds construction up considerably and reduces the possibility of making errors. Smart Kit boards also come pre-drilled and with the outline of the components and their identification printed on the component side to make construction easier. To protect the board during storage from oxidation and assure it gets to you in perfect condition the copper is tinned during manufacturing and covered with a special varnish that protects it from getting oxidised and also makes soldering easier.
Soldering the components to the board is the only way to build your circuit and from the way you do it depends greatly your success or failure. This work is not very difficult and if you stick to a few rules you should have no problems. The soldering iron that you use must be light and its power should not exceed the 25 Watts. The tip should be fine and must be kept clean at all times. For this purpose come very handy specially made sponges that are kept wet and from time to time you can wipe the hot tip on them to remove all the residues that tend to accumulate on it. DO NOT file or sandpaper a dirty or worn out tip. If the tip cannot be cleaned, replace it. There are many different types of solder in the market and you should choose a good quality one that contains the necessary flux in its core, to assure a perfect joint every
time.
DO NOT use soldering flux apart from that which is already included in your solder. Too much flux can cause many problems and is one of the main causes of circuit malfunction. If nevertheless you have to use extra flux, as it is the case when you have to tin copper wires, clean it very thoroughly after you finish your work. In order to solder a component correctly you should do the following:
- Clean the component leads with a small piece of emery paper.
- Bend them at the correct distance from the component’s body and insert the component in its place on the board.
- You may find sometimes a component with heavier gauge leads than usual, that are too thick to enter in the holes of the p.c. board. In this case use a mini drill to enlarge the holes slightly. Do not make the holes too large as this is going to make soldering difficult afterwards.
- Take the hot iron and place its tip on the component lead while holding the end of the solder wire at the point where the lead emerges from the board. The iron tip must touch the lead slightly above the p.c. board.
- When the solder starts to melt and flow, wait till it covers evenly the area around the hole and the flux boils and gets out from underneath the solder. The whole operation should not take more than 5 seconds. Remove the iron and leave the solder to cool naturally without blowing on it or moving the component. If everything was done properly the surface of the joint must have a bright metallic finish and its edges should be smoothly ended on the component lead and the board track. If the solder looks dull, cracked, or has the shape of a blob then you have made a dry joint and you should remove the solder (with a pump, or a solder wick) and redo it.
- Take care not to overheat the tracks as it is very easy to lift them from the board and break them.
- When you are soldering a sensitive component it is good practice to hold the lead from the component side of the board with a pair
of long-nose pliers to divert any heat that could possibly damage the component.
- Make sure that you do not use more solder than it is necessary as you are running the risk of short-circuiting adjacent tracks on the board, especially if they are very close together.
- When you finish your work, cut off the excess of the component leads and clean the board thoroughly with a suitable solvent to
remove all flux residues that may still remain on it.

The project is a very easy one, as the components which form the circuit are very few and their outlines have been clearly stencilled on the board for you. The only unusual thing is that the transistor must be soldered from the copper side of the board. This is, however, common with UHF devices and is usually done to avoid the introduction of stray capacitances between the transistor’s leads that could possibly alter the behaviour of the circuit. Be careful to make good joints and try to keep the component leads as short as possible because of the very high frequencies involved. Solder first of all the pins and the resistors. The coils are supplied ready to be soldered on the printed circuit and you
should take care not to deform them in the process. Place then the capacitors and solder the diodes carefully trying to avoid overheating them and making sure that they are correctly aligned. Solder the transistor in its place, after you have finished soldering the other components, to avoid overheating it, and be careful to align it according to the diagram included in the instructions. (The lettering on the transistor body should be facing away from the copper). The input of the circuit is at point 4 and ground and the output at point 1 and ground. The battery is connected using the battery clip supplied at points 2 (-) and 3 (+), and is a miniature 9 V one, alkaline if you prefer. For best performance and to avoid unwanted interference during operation it is recommended to place the circuit in a small metal box, and use suitable connectors mounted on the box for the external connections. You can use a box large enough to house the amplifier and the battery or you can use an external power supply, but remember to use a FEED THROUGH capacitor on the positive supply line, where it passes through the metal box. If you plan to use the amplifier for both VHF and UHF TV reception you should use a common VHF/UHF mixer before the amplifier’s input.

PARTS

R1 = 120 Ohm (brown, red, brown)
R2 = 1,5 KOhm (brown, green, red)
R3 = 270 Ohm (red, violet, brown)
R4 = 82 KOhm (gray, red, orange)
C1,C5 = 100pF (ceramic)
C2,C3 = 1nF (ceramic)
C4 = 2,2pF (ceramic)
D1,D2 = 1N4148 diode
Transistor = BFR90, BFR91, BFW92
Misc = PCB, 6pins, solder, 9V battery clip

Sunday, October 5, 2014

regulator 3A switching circuit and explanation

When compared to linear voltage regulators the switching voltage regulators are much power efficient. In the case of linear voltage regulators the difference between the input and output voltage is just wasted and for switching regulators there is almost no such wastage and that’s why the switching regulators have great power efficiency ranging up to 85% . In simple words, the switching regulator operates by taking small bits of energy from the input voltage source and then transferring it to the output with the help of a solid state switch and a control circuitry. Since the switching element is either fully open or closed at any moment, no energy is wasted across it. The control circuit controls the duty cycle of the solid state switch which in turn determines rate at which energy is transferred to the output.

The electronic circuit given here is of a simple and low cost switching regulator using the IC LM317 that can deliver up to 3A of current. The input voltage range of this circuit is between 8 to 35V DC and the output voltage can be adjusted between 1.8 to 32V DC. The output voltage can be adjusted by using the POT R4.

Circuit diagram.

Notes.

Assemble the circuit on a good quality PCB.
C1 must be a solid tantalum capacitor.
Transistor T1 and IC1 require heat sinks.
L1 can be a 600uH inductor.

Tuesday, September 23, 2014

Adjustment power supply values 1 25 15V Max current 0 5 amp circuit

This is power supply that have Voltage output fine the value has 1.25-15V. From by Output current that be valuable about 0.5 amp that 12V and 0.2 amp that 15V.
When Volt , from 220V houses reach transformer. It will modify Volt 220V to be 18VAC already to change rectifier circuit. Which D1, D2, C1 and R1 wasp be Full wave rectifier circuit. For modify DCV to ACV to a signal DCV. It make get a signal DCV that have voltage at pin 3 of IC1 be 20V. From that time DCV signal this reach fight DC Regulator circuit. Which use IC number LM317.

This circuit will perform to maintain one’s position Voltage smoothly. Which level output voltage at get this will go out the way pin 2 of IC1. By have capacitors C2 be voltage filter in order that voltage output level of the circuit is will high class modify to follow fining. The performing fee withstands VR1 there.

from:eleccircuit.com

Sunday, September 21, 2014

Thermistor Temperature Monitor Circuit and explanation

Heres a simple op-amp circuit with a NTC thermistor as sensor that will trigger a relay when a preset temperature is reached. There is no hysteresis in this circuit, so that if the temperature changes rapidly, then the relay may switch rapidly.

This sensor circuit uses an ordinary NTC thermistor with a resistance of 47k at room temperature. A suitable part from Maplin Electronics is FX42V. The circuit is set in balance by adjusting the the 47k potentiometer. Any change in temperature will alter the balance of the circuit, the output of the op-amp will change and energize the relay. Swapping the position of the thermistor and 47k resistor makes a cold or frost alarm.

At room temperature (25 degrees Celsius) a 47k NTC thermistor resistance is approximately 47k. The non-inverting op-amp input will then be roughly half the supply voltage, adjusting the 47k pot should allow the relay to close or remain open. To calibrate the device, the thermistor ideally needs to be at the required operating temperature. If this is for example, a hot water tank, then the resistance will decrease, one way to do this is use a multimeter on the resistance scale, read the thermistors resistance and then set the preset so that the circuit triggers at this temperature.

Please note that if the temperature then falls, the relay will de-energize. If the environment temperatures changes rapidly, then the relay may chatter, as there is no hysteresis in this circuit.

Hysteresis, allows a small amount of "backlash" to be tolerated. With a circuit employing hysteresis, there will be no relay chatter andthe circuit will trigger at a defined temperature and require a different temperature to return to the normal state. Hysteresis can be applied to the circuit using feedback, try a 1 Mega resistor between op-amp output, pin 6 and the non-inverting input pin 2 to give the circuit hysteresis.

Without offset null adjustment, the output of the 741 IC will be around 2 Volts (quiescent) swinging to nearly full supply when triggered. The 4.7k and 1k resistor form a potential divder so that under quiescent conditions the transistor will be off. Quiescent or steady state means no signal, or in this case (when the temperature does not cause the output to swing to full voltage).

Source: Temperature Monitor