Showing posts with label circuit. Show all posts
Showing posts with label circuit. Show all posts

Thursday, November 20, 2014

Solve buzzing and noise on the amplifier circuit

Power amplifiers that we sometimes raises a raft of small drone as groundingless than perfect.The following are some ways to cope with the hum of the power amplifier: 

1. Keep sensitive circuits of the transformer, casing dimensions are not too small.One blog even suggested to use two-bok, bok special one for the transformer. For the toroid transformer or amplifier with a large transformer, should only contain a series of power amps, with no tone control. 
2. Change the position of the transformer, side by side into the lower side (the transformer is high) withfacing a series of sensitive posts 
3. Use a spacer on each PCB board as high as half the height of the transformer, eg as high as 2.5 cm or more so that the PCB board parallel to the core / center of the transformer, here the effect of the weakest fields. 
4. We recommend using a stereo module instead of two mono modulesThis avoids wiring errors. If forced to, try to sizecable between the right and left modules as long and as short as possible. 
5. Should take the ground path for the speaker of ct ct elco instead of the transformer,if the board pcb mounted two big elco (like elco power supply), takeground path of the speakers here, and check to hear! 
6. Power supply for radio (TX or RX) is very sensitive, use a capacitor4x100nf, 4 pairs of these capacitors in parallel to each mem-diode (bridge). 
7. At the tone control circuit IC op-amp that uses a symmetric power supply,sufficient ground wiring is taken from the signal ground wires only. shouldIC power supply (7812) installed near the main power supply, notmounted near the tone control. 
8. Always use a stereo cable shrouded perfect (color stereo cablered-white-covered ground and wrapped in transparent skin. 
9. For power supply, use capacitors of 2200uF per ampere elco 
10. Zoom and ground wires as short as possible, especially a pair of elco (ct line between elco) power supply (can be tried for the amplifier blazer) 
11. For the amplifier should be mounted to the computer casing when not in the ground soil is diground PC casing soil 
12. Pairs of each kit to the circuit without passing groundnya nut / baud / spacer. Do not let the existing ground line at the hole pcb connected to the casing / box. Do not follow this ground. ground attached to the casing should have one. if necessary use a plastic spacerovercome the noise: 
1. Use the active component (IC) that qualified as TL084, TL074, notLM324. LM324 any brand of noise. TL084 is more guaranteed authentic yellow (ST), not white. For now, the IC TL084 is printed white-work unstable frequencyhigh (treble breaks and more noise). For IC 4558 (NE5532) use plain white silk screening JRC4558D or TL072 - TL082 yellow, LF353 noise. LM741 (NE5534) can be replaced with the Hitachi HA17741, LF351 noise may also, has never been tried.we do not have to look for the brand and the price is more expensive because it is the most low noise. 
2. If necessary, the circuit power amplifier OCL, lowering its gain by lowering the value ofresistor in the path gain from 33k to 22k speaker, mimics the gain-clone lower amplifier noise. 
3. Should simplify the circuit, the circuit is too complex is more susceptible to noise and interference. 
4. Should then potentio / volume mounted on the input-power amplifier, such as professional amplifier without tone control.
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Wednesday, November 19, 2014

Simple LED Emergency Light Circuit


This LED emergency light project is simple, cheap and easy to build. The circuit do the charging of the battery and when the main source is not available such as in brownouts, the white LEDs automatically turn on. 
Initially, the voltage output  from 220V to 12V converter is fed to the input of LM317 regulator. Then this voltage is regulated down to 7.37V using 240 ohms and 1.2K resistor combination (see LM317 Calculator).
At this instant, the battery is in charging mode and the transistor Q1 is off. Indicator LED serves two purpose, one primarily is to give us idea that the battery is charging and another is to ensure that the Q1 is off.
During brownouts, the transistor Q1 is on and delivers current to 16 white LED of about 20mA each, thus a fully charged battery (6V/4.5Ah) can last up to 14 hours.

The charger has no built in over-current control but still it protects the battery from overcharging since the charging voltage is set only to 7.4V.


Project materials:
1pc - transformer - 220V to 12V-0-12V , center tap 12VA
16pc - 120 ohms resistor 1/4 W
16pc - white LED min 3V@30mA
1pc - red LED
1pc - 1000uF/25V electrolytic capacitor
3pc - 1N4001 diode
1pc - LM317 regulator
1pc - 1.5K resistor 1/4W
1pc - 240 ohms resistor 1/4W
1pc - 1.2k resistor 1/4W
1pc - 9012 pnp transistor or any of much higher capacity
1pc - 6V 4.5ah battery
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Tuesday, November 18, 2014

Doubler Digital Frequency circuit

Doubler Digital Frequency circuit includes a simple and easy to understand. Digital Frequency Doubler circuit application contained in the system electronics such as audio-producing organ, or keyboard. The function of this series Digital Frequency Doubler for multiplying two input frequencies.

The process of multiplying 2 on scales in an organ in principle is like this series Digital Frequency Doubler. Example of rising to a ringing tone DO RE then electronically technique in it is by multiplying the two frequency bands such as this series Digital Frequency Doubler.
Digital Frequency Doubler.
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Monday, November 17, 2014

Water to activated Relay circuit



Water
Water to activated Relay circuit
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Sunday, November 16, 2014

Magnetic Switch Circuit

Magnetic switch is a circuit which can respond to magnetic fields that were around the sensor. The series of magnetic switches uses sensors in the form of limit switches that provide an additional metal plate that can respond to a magnet. Magnetic switch circuit is made ​​with an NE555 monostable multivibrator and a flip-flop togle from IC CD4013. The series of magnetic switches uses 12VDC supply voltage and the magnetic circuit is mounted indicator switch which serves to give a signal when the sensors respond to magnetic fields using the LED D1. Here is a complete range of magnetic switches.

Magnetic

If the limit switches (sensors), active (connected) then it will get multivibrator NE555 triger signal and provides output pulses to be used to provide input signals to the flip-flop togle Relay K1 and active. Then when the sensors (limit switches respond to the magnetic field again, the multivibrator will give togle pulse as input to the flip-flop relay K1 and non-active.

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Magnetic Proximity Switch Circuit

Here is the circuit diagram of a magnetic proximity switch that finds a lot of applications in abounding fields.The ambit is based on a alluring reed switch(S1) as the adjacency sensor. A monostable multivibrator based on NE555 (IC1) and a toggle cast bomb based on CD4013 (IC2) does the blow of the circuit.

When a allurement is accomplished in adjacency of S1 it closes to accord a abrogating activate at pin 2 of IC1.The achievement of IC1 goes top for a time determines by R2 and C2.This clocks the IC2 active as a toggle cast flop.The achievement (pin 1 ) of IC2 goes top and the transistor Q1 is biased to ON.The broadcast is activated and so do the accessories affiliated to the relay.The LED D1 glows if IC1 is triggered.

When a allurement is accomplished in adjacency of S1 it closes to accord a abrogating activate at pin 2 of IC1.The achievement of IC1 goes top for a time determines by R2 and C2.This clocks the IC2 active as a toggle cast flop.The achievement (pin 1 ) of IC2 goes top and the transistor Q1 is biased to ON.The broadcast is activated and so do the accessories affiliated to the relay.The LED D1 glows if IC1 is triggered.
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Saturday, November 15, 2014

ELECTRONIC FUSE CIRCUIT

The Fuse is a type of electrical equipment to the poor. Because it sacrifices itself. To protect the safety devices in the circuit. In the case of current flow in circuit too much. Until it melted. Due to an error in the circuit. The structure is a glass cylinder with an alloy of lead wire is connected between the two terminals. When the current through it too much, Alloy within is temperature rises until the melting. Makes wires were cut off.

In some experiments a electronic circuits require a fuse protection. Circuit may be difficult. Because, often short, to change the fuse every time. Thus wasting time.

To solve this problem, we Build this electronic fuse, so instead of plain fuses. By it can cut off the current immediately. When a short circuit as well. But can work immediately. Just press the reset button only. Convenient and economical than using plain fuses. We also can set up and cut off current as you want.

How the electronic fuse works?

The electronic fuse that we use in this project is in Figure 1. Which will include important devices are transistors of 2 pcs, and Electronic devices in thyristors type of 1 piece works, together.


In the Figure 1, This project across between the power supply and load that will be applied immediately, When a input of electronic fuse to the power supply. Then, Q1-transistor conduct current causes a Q2-Darlington transistor works as well, collector and emitter will conduct current by resistor R3 out to the Load that connected with the pin output(K2).

When the load use current will cause has a voltage across R3. If load use high current will cause voltage across R3 too much as well. As Ohm’s law. And When Load use current until voltage across R3 more than 0.6 volts. Then, this voltage will trigger to SCR1 conduct current.

This SCR or silicon controlled rectifier will works or conduct when get trigger at pin gate (G), and It will bring current indefinitely.
Although no trigger it.

How to stop the Works is remove its power supply there. We will bring this feature to use in our circuit. When voltage across R3 over 0.6 volts, the SCR1 will conduct , makes voltage at base of Q2 drop to level that transistor cannot conduct high current.

From the original. collector and emitter has conduct current into stop, causes current flow to load next step, until push reset switch-S1 ,to separate SCR1 out of circuit. After that Q2 will start conduct current again.

In the section of Q1, LED1 and R2 there, will be together serving as a constant current circuit. To Q2 conduct when Normal conditions, and stop current to Q2, when SCR1 conduct current to ground.

Determination current of fuse

The current of fuse that you want to cut off circuits, can easily set easily from changing R3 which is a current detector. When we use Ohm’s law, which circuit will cut current when voltage drop across R3 is 0.6 volts.

Based this condition, we can find the right resistor with the following formula.
R3 = 0.6/I ….(1)

We set I is the current that want to start cutting circuit. (Is measured in amps.)

For example want to start cutting at 500 mA will must connect R3 are :

R3 = 0.6/0.5 = 1.2 ohms.

Thus, If you need the electronic fuse cut current at 500 mA, it must use R3 of 1.2 ohms. The rate watt resistant of resistor values (P) from:

P = 0.6x current value (amperes) ….(2)

Will have P = 0.6×0.5 = 0.3 watts

So must select the Resistor of 1.2 ohms , the power rate is 0.3 watts But resistor size 0.3 watts no selling, so use 0.5 watts instead.

From example can easily define current of electronic fuse. Who Those who want to use fust in others currents, can It can be calculated from equation (1) and (2) to calculate Resistance (R3).

But should be less than 1 Amperes, because that Darlington transistor unbearable. And should be used only in the voltage of 10-25 volts.

The components List

Resistors ¼ W + 5%
R1———————4.7K
R2———————68ohm
R3——————— see text

Semiconductors
Q1—————-BD140___100V 1.5A PNP transistor
Q2—————-BD679___100V 2A NPN transistor
LED1 (Light emitting Diode) Red 5 mm
SCR1————-TIC106E

Other parts
K1-K3 terminal into PCB
S1 Switch, press the off, released stick, etc.
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Friday, November 14, 2014

Voltage Doubler Circuit Using NE555

The circuit diagram of a very simple voltage doubler using NE555 timer is shown here. Here IC NE555 is wired as an astable mutivibrator operating at around 9KHz. The base of the two transistors (Q1 and Q2) is shorted and output of the astable multivibrator (pin 3) is connected to it. When the output of astable multivibrator is low, Q1 will be OFF and Q2 will be ON. The negative terminal of the capacitor C3 will be shorted to ground through T2 and it will be charged to the input supply voltage. When the output of the astable multi vibrator is high, transistor Q1 will be ON and transistor Q2 will be OFF. The capacitor C4 will be charged to the voltage across capacitor C3 plus the input supply voltage (that is double the input voltage). This is how the circuit works.

This voltage doubler circuit can deliver only up to 50mA output current and above that current limit the output voltage will be dramatically reduced. The actual output voltage will be around 19V for a 12V DC input and also the output voltage will be a bit unstable. Anyway, for low current applications this circuit is well enough.

Circuit Diagram


 

Important Points

  • The circuit can be assembled on a vero board.
  • The output current should not be allowed to exceed 70mA.
  • IC1 must be mounted on a holder.
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Thursday, November 13, 2014

TDA2030 18W 18W Stereo Hi Fi Audio Amplifier Diagram Circuit

2 x 18W Hi-Fi Stereo Power Amplifier based around two TDA2030 ICs. It has good input sensitivity, low distortion, good operating stability and full protection against overloads and output short-circuits. It can be used as a booster amplifier for existing small systems or to drive a second pair of speakers besides the ones already connected to the system. The board needs a symmetrical power supply of ±18Vdc/3A and can be connected to loads of 8 or 4 Ohm. Large heat sink is required for this circuit. Diagram shown below indicates only left channel. Make two circuits for for stereo version.Picture of the project:
18 watt + 18 watt hi fi stereo audio power amplifier circuit schematic diagram
18+18 Watt Hi-Fi Stereo Audio Amplifier Circuit Diagram

Circuit Diagram:
18 watt + 18 watt hi fi stereo audio power amplifier schematic circuit diagram
Diagram Shows Only One Channel

Parts:R1 = 22K
R2 = 680R
R3 = 22K
R4 = 1R-1w
D1 = 1N4001
D2 = 1N4001
C1 = 1uf-25V
C2 = 22uF-25V
C3 = 100nF-63V
C4 = 100nF-63V
C5 = 100uF-25V
C6 = 100uF-25V
C7 = 220nF-63V
IC = TDA2030If it does not work:
  1. Check your work for possible dry joints, bridges across adjacent tracks or soldering flux residues that usually cause problems.
  2. Check again all the external connections to and from the circuit to see if there is a mistake there.
  3. See that there are no components missing or inserted in the wrong places.
  4. Make sure that all the polarized components have been soldered the right way round.
  5. Make sure the supply has the correct voltage and is connected the right way round to your circuit.
  6. Check your project for faulty or damaged components.

Technical Specifications:
  • Supply voltage = ±18Vdc/3A symmetrical (see text)
  • Current consumption = 3A maximum
  • Input impedance = 500K Ohms
  • Input sensitivity = 250 mV
  • Signal to noise ratio = 80 dB
  • Frequency response = 20 - 20,000 Hz ± 1 dB
  • Distortion = 0.5 % maximum
  • Load impedance = 4 - 8 ohm
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Wednesday, November 12, 2014

7812 and 7912 Dual Regulator circuit with explanation


Voltage Regulators low ability burning IC 78W alternation acclimated in our chart is now so bargain they are an economical another to simple regulators NPN-stabilizers. In addition, they action the allowances of bigger regulation, accepted absorbed / abbreviate ambit aegis to 1000 mA blow and calefaction bottomward if the electricity disperses too. Indeed, is not the alone way for these drives can be damaged polarity is incorrect or boundless ascribe voltage. RegulatorsAlternation 78W to affectionate of break 8V ascribe voltage of about 35V, while the blazon 24v bear 40V. Of course, of course, that regulators will not assignment with such an important ascribe cogwheel achievement as it would advance to boundless ability is dispersed. All controllers will bear the 78Walternation 1000mA accepted best accepted ascribe cogwheel voltage achievement of beneath than 7V. Otherwise, too broadcast power, thereby bringing the blaze extinguished.

Two transformers were acclimated to footfall voltage 230-250V AC ascribe power. It articles ability transformers 6-0-6V accessory terminals. This achievement is fed into the rectifier and clarify capacitor. Filtered IC6 that served 3-pin voltage regulator that provides a adapted achievement + 5V. It is acclimated to accredit the DPM system. It additionally comes as the arrangement voltage antecedent temperature accuracy.

Other articles transformers with a accommodation of 12-0-12V at its accessory terminals. The centermost was accustomed as a bubbler in the antecedent case. The added two accessory terminals are fed archrectifier complete application diodes. Achievement recovered is filtered application a capacitor C5 and C6 for aliment and IC7 IC. In-8 IC7, which are 3-pin regulators accommodate achievement voltage of ± 8V. These two voltages are arresting generator. TO-8V ability antecedent is activated to the temperature of the network, and the advertence voltage. It is additionally all-important to +12 V and-12V food for the accomplishing of operational amplifiers. This can be calmly done application a 12V zener diodes. The achievement of archrectifier is absorbed to the +12 V and-12V, respectively, application two zener diodes. In the zener achievement is fed to the terminals of the operational amplifier supply. For supply

for operational amplifiers charge not be actual able in acclimation + 12V, the use of Zener diodes be costly.

For the testing of cyberbanking apparatus voltage aloft 50 V is required. This can be accomplished through quadruple the alternation tension. It consists of four diodes and four electrolytic capacitors. Unreasonable Administration Accessory 12-0-12V is affiliated to quadruple string. Quadrupled achievement of the ambit is 68V to ground.

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Tuesday, November 11, 2014

LV4700P bassed 4x24 watt car audio amplifier Diagram Circuit


This car audio amplifier electronic project is based on the LV47004P audio IC , specially designed for car audio applications . The LV4700P IC is manufactured by Sanyo Semiconductors and is a 4-channel BTL power amplifier that is developed for car audio system.
Pch DMOS in the upper side of the output stage and Nch DMOS in the lower side of the output stage are complimentary.
High power and high quality sound are realized by that.
This IC incorporate various functions like : standby switch, muting function, and various protection circuit ; necessary for car audio system. Also, the LV47004P audio IC has a self-diagnosis function.

This 4x24 watt car audio amplifier based on LV4700P circuit can operate from a 9 to 16 volts DC power supply circuit , but typically is recommended a 14.4 volt DC power supply .
The output power that can be provided by this car audio amplifier circuit is around 24 watt per channel with thd 10% , on a 4 ohms load . In same conditions this 4x24 watt car audio amplifier based on LV4700P can provide a maximum output power of 17 watt per channel with THD 1% .
As you can see in the schematic circuit , the design of this power amplifier project is very simple , requiring few external electronic parts .
By varying the value of input capacitor, low-frequency characteristic can be improved.
For pop noise prevention, it is recommended to use the muting function at the same time.
Please turn on the muting function simultaneously with power supply on when the amplifier is turned on. Next, turn off the muting function after the output DC potential stabilization. When the amplifier is turn off, turn off the power supply after turning on the muting function.
To prevent damage due to overheating process the LV47004P audio IC must be heatsinked .

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PIC16F84A based LC Meter circuit with explanation

PIC16F84A
This is one of the most accurate and simplest LC inductance / capacitance Meters that one can find, yet one that you can easily build yourself. This LC Meter allows to measure incredibly small inductances starting from 10nH to 1000nH, 1uH to 1000uH, 1mH to 100mH and capacitance from 0.1pF up to 900nF. LC Meter’s circuit uses an auto ranging system so that way you do not need to spend time selecting ranges manually. Another neat function is the “Zero Out” switch that will reset the initial inductance / capacitance, making sure that the final readings of the LC Meter are as accurate as possible. 
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Sunday, November 9, 2014

Input Impedance Booster Circuit

The input resistance of a.c.-coupled op amp circuits depends almost entirely on the resistance with which the d.c. setting is determined. If CMOS op amps are used, the input resistance is normally high, currently up to 10 MΩ. If a higher value is needed, a bootstrap circuit may be used. This enables the input resistance to be boosted artificially to a very high value, indeed In the circuit shown in the diagram, resistor R1 sets the d.c. point for IC1a. The terminal of the resistor linked to pin 7 of IC1 would normally be at earth potential, so that the input impedance would be 10 MΩ. Connecting the other terminal of the resistor to earth via IC1a and network C2-R3-R2 as far as d.c. is concerned results in the requisite d.c. setting of the op amp.

Circuit diagram:
Input Impedance Booster II Circuit Diagram

As far as alternating voltages are concerned, the input signal is fed back so that only a tiny alternating current flows through R1. Therefore, Rin=R1[(R2+R3)/R3]. With resistor values as specified, Rin is about 1 GΩ. One aspect must be borne in mind: the numerical value of (R2+R3)/R3 must not exceed 0.99. This means that the value of R3 cannot be less than 100 kΩ if the value of R2 is 10 MΩ. If these conditions are not met, the circuit will become unstable.

Copyright: Elektor Electronics
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Saturday, November 8, 2014

USB Switch Schematic Circuit Diagram

Anyone experimenting or developing USB ported peripheral hardware soon be comes irritated by the need to disconnect and connect the plug  in order to reestablish communication with the PC. This process is necessary for example each time the peripheral equipment is reset or a new version of the firmware is installed. As well as tiresome it eventually leads to excessive contact wear in the USB connector. The answer is to build this electronic isolator which disconnects the peripheral device at the touch of a button. This is guaranteed to reduce any physical wear and tear and restore calm once again to the workplace. 

Circuit image :
 
USB Switch Schematic Circuit Image

The circuit uses a quad analogue switch type 74HC4066. Two of the switches in the package are used to isolate the data path. The remaining two are used in a classic bistable flip-flop configuration which is normally built using transistors. A power MOSFET switches the power supply current to the USB device.  Capacitor C2 ensures that the flip flop always  powers-up in a defined state when plugged  into the USB socket (‘B’ in the diagram). 

The  peripheral device connected to USB socket ‘A’  will therefore always be ‘not connected’ until  pushbutton S2 is pressed. This flips the bistable, turning on both analogue gates in the data lines and switching the MOSFET on. The  PC now recognises the USB device. Pressing  S1 disconnects the device.
Circuit diagram :

USB Switch Schematic Circuit Diagram

The circuit does not sequence the connections as a physical USB connector does; the power supply connection strips are slightly longer than the two inner data carrying strips to ensure the peripheral receives power before the data signals are connected. The electronic switch does not suffer from the same contact problems as the physical  connector so these measures are not required in the circuit. The  simple circuit can quite easily be constructed on a small  square of perforated strip-board. 

The design uses the 74HC(T)4066 type analogue switch, these have  better characteristics compared to the standard 4066 device. The USB switch is suitable for both low-speed (1.5 MBit/ s) and full-speed (12 MBit/s) USB ports applications but the proper ties of the analogue switches and perf-board construction  will not support hi-speed (480 MBit/s) USB operation.
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Thursday, October 30, 2014

TDA8551 AF Amplifier With Digital Volume Control Diagram Circuit

The Philips Semiconductors TDA8551 is a small audio amplifier with an integrated volume control. When operated from +5 V, it delivers a nominal output power of more than one watt into 8 ohms. It can also be used over a supply voltage range of +2.7 to +5.5 V, with correspondingly reduced output power. The output volume can be adjusted from –60 dB to +20 dB in 64 steps, using a set of up and down push-buttons. The shared UP/DOWN input for the up and down switches has three states. If it is ‘floating’, which means that both of the switches are open, the volume remains unchanged. A pulse to earth decreases the volume by 1.25 dB, while a positive pulse increases the volume by 1.25 dB.

AFWhen the power is switched on, the internal counter takes on the –20 dB setting. An additional input (MODE) allows the amplifier to be switched from the operating state to the mute or standby state. If this input is held at the earth level, the amplifier is operational. If +5 V is applied to this pin, the TDA8551 enters the Standby mode, in which the current consumption drops from the typical operational level of 6mA to less than 10µA. Finally, the MODE input can be used as a mute input by applying a voltage of 1 t0 3.6 V to this input. This voltage can be provided by a connection to the SCR pin, which lies at half of the operating voltage and to which a filter capacitor is connected.

TDA8551/TDA8551TThe loudspeaker is connected in a floating configuration between the two outputs of the bridge amplifier in the TDA8551. This provides the desired output power level, in spite of the low supply voltage. For headphone applications, which do not need as much output power, you can connect the headphone between earth and one of the outputs, via an electrolytic coupling capacitor. You can make a stereo headphone amplifier in this way, using two TDS8551 ICs. The TDA8551 is housed in a DIP8 package. The SMD version is the TDA8551T, in an SO8 package
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Protector Monitors Current Circuit Diagram

This is a simple Protector Monitors Current Circuit Diagram. This circuit uses a 0.1O 1W resistor connected in series with the output of a power amplifier. When the amplifier is delivering 100W into an 8O load, the resistor will be dissipating 1.25W. The resulting temperature rise is sensed by a thermistor which is thermally bonded to the resistor. The thermistor is connected in series with a resistor string which is monitored by the non-inverting (+) inputs of four comparators in an LM339 quad comparator. All of the comparator inverting inputs are connected to an adjustable threshold voltage provided by trimpot VR1. As the thermistor heats up, its resistance increases, raising the voltage along the resistor ladder.

Loudspeaker Protector Monitors Current Circuit diagram:

loudspeaker-protector-circuit-diagram-monitors-current Loudspeaker Protector Circuit Diagram

When the voltage on the non-inverting input of each comparator exceeds the voltage at its inverting input, the output switches high and illuminates the relevant LED. NOR gate latches are connected to the outputs of the third and fourth comparators. When the third comparator switches high, the first latch is set, turning on Q1 and relay 1. This switches in an attenuation network (resistors RA & RB) to reduce the power level. However, if the power level is still excessive, comparator 4 will switch, setting its latch and turning on Q2 and relay 2.

This disconnects the loudspeaker load. The thermistor then needs to cool down before normal operation will be restored. The values of R1-R4 depend on the thermistor used. For example, if a thermistor with a resistance of 1.5kO at 25°C is used, then R1 could be around 1.5kO and R2, R3 and R4 would each be 100O (depending the temperature coefficient of the thermistor). The setup procedure involves connecting a sinewave oscillator to the input of the power amplifier and using a dummy load for the output. Set the power level desired and adjust trimpot VR1 to light LED1. Then increase the power to check that the other LEDs light at satisfactory levels.


 Author: David Devers - Copyright: Silicon Chip Electronics
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Simple Soldering Iron Inverter Circuit Diagram

This is a Simple Soldering Iron Inverter Circuit Diagram. This is a simple but inexpensive inverter for using a small soldering iron (25W, 35W, etc) In the absence of mains supply. It uses eight transistors and a few resistors and capacitors. Transistors Q1 and Q2 (each BC547) form an astable multivibrator that produces 50Hz signal. The complementary outputs from the collectors of transistors Q1 and Q2 are fed to pnp Darlington driver stages formed by transistor pairs Q3-Q5 and Q4-Q6 (utilising BC558 and BD140). The outputs from the drivers are fed to transistors Q7 and Q8 (each 2N3055) connected for push-pull operation.  Use suitable heat-sinks for transistors Q5 through Q8. A 230V AC primary to 12V-0-12V, 4.5A secondary transformer (T1) is used.


Soldering Iron Inverter Circuit Diagram


Soldering

The centre-tapped terminal of the secondary of the transformer is connected to the battery (12V, 7Ah), while the other two terminals of the secondary are connected to the collectors of power transistors T7 and T8, respectively. When you power the circuit using switch S1, transformer X1 produces 230V AC at its primary terminal. This voltage can be used to heat your soldering iron. Assemble the circuit on a generalpurpose PCB and house in a suitable cabinet. Connect the battery and transformer with suitable current-carrying wires. On the front panel of the box, fit power switch S1 and a 3-pin socket for connecting the soldering iron. Note that the ratings of the battery, transistors T7 and T8, and transformer may vary as these all depend on the load (soldering iron).



Author : Sanjay Kumar
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VHF UHF HF active antenna electronic diagram

A very simple and efficiency active antenna electronic project can be designed using this electronic schematic circuit that is based on transistors. This active antenna electronic project is useful for a wide range of RF frequencies covering three RF bands HF , VHF and UHF . This simple active antenna is designed to amplify signals from 3 to 3000 MegaHertz, including three recognized ranges: 3-30Mhz high-frequency (HF) signals; 3-300Mhz veryhigh frequency (VHF) signals; 300-3000MHz ultra-high (UHF) frequency signals.

This HF VHF UHF active antenna contains only two active elements : Q1 (which is an
VHF
MFE201 N-Channel dual-gate MOSFET) and Q2 (which is an 2SC2570 NPN VHF silicon transistor). Those transistors provide the basis of two independent, switchable RF pre-amplifiers. Two DPDT switches play a major role in this circuit , switch S1 used to select one of the two pre-amplifier circuits (either HF or VHF/UHF) and switch 2 is used to turn off the power to the circuit, while coupling the incoming RF directly to the input of the receiver.This circuit must be powered from a simple 9 volt DC power circuit ( or a 9 volts battery) and is very useful for use as an indoor antenna
S2 is useful to give to receiver nonamplified signal access to the auxiliary antenna jack, at J1, as well as the on-board telescoping whip antenna.
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Wednesday, October 29, 2014

CD4017 Digital Dice Circuit

A electronic acquaintances was seeking a star as circuits in vogue your at no cost point in time,a shameful and uncomplicated to made.This dice digital circuit would occur a favorite of all and sundry, by using it to flaunt the records. As you switch to a spin button before it like is tossing a dice. Looks like a random form normally.

CD4017

A focal point of this circuit,an a secure oscillator 1Khz with IC 555 and RC networks,it resolve be located output to IC2 is Decade counter IC - 4017. After I focus inedible the spin switch, it will be converted to a binary input with a diode matrix D1-D9 (1N4148 before numeral 1N914) and so therefore untouched to a 7 segment put on show with a decoder drive IC refusal. CD4511 (IC3). The brightness of the numeric display, may well occur customized by adjusting the quantity of R3.

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Tuesday, October 28, 2014

Car Backup Alarm Circuit

The brake lights of the automobile trigger this circuit on and off. This save the annoyance of the alarm when it is not needed. This is an older circuit which was published in Popular Electronics Magazine, but still a good circuit today.
Car
Car backup alarm circuit diagram
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