Circuit Diagram Knowledge: with

Showing posts with label with. Show all posts

Showing posts with label with. Show all posts

Wednesday, November 19, 2014

Preamplifier Microphone with 2 Transistor

Microphone preamplifier or often known as mic preamp can be made use simplemicrophone preamplifier circuit as follows. 2 microphone preamplifier circuit uses 2transistors are PNP and NPN transitor amplifier.

Front of the microphone amplifier orpreamplifier microphone 2 transistor uses a system of dc negative feedback through R6which serves to provide stability strengthening. Level output signal from the microphonepreamplifier is controlled by potentiometer P1. Input signal that can be responded well by this microphone preamplifier is 0.2 - 200mV and 1V RMS output will result.

   Component List      P1 2k2
     R1, R2, R3 100K 1/4W
     R4 8K2 1/4W
     R5 68R 1/4W
     R6 6K8 1/4W
     R7, R8 1K 1/4W
     R9 150R 1/4W
     C1 1uF 63V
     C2, C3, C4 100uF 25V
     C5 22uF 25V
     Q1 BC560C
     Q2 BC550C

Microphone preamplifier circuit two transistors in the show above is preampmic suitable for home audio system on the stereo. This microphone preamplifier circuit requires supply voltages 9Vdc.

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Wednesday, November 12, 2014

indicator alarm for Water level circuit with explanation

This electronic circuit is a simple water level indicator alarm that is based on few transistors . The circuit is very simple and it has a very low current consumption , so you can use a 9 volts battery to powering this water level indicator alarm . This water level indicator alarm electronic circuit can be used even for rain alarm or short circuit alarm , a resistance with a value from 0 to about 1 M ohm will trigger it . The Q1 transistor acts as a switch which applies current to the unijunction relaxation oscillator Q2 . The signal frequency of the alarm circuit is give by the values and ratios of the C1 / R2 .

If you don’t have the transistors marked on the schematic diagram you can replace them almost with any similar types . As you can see in the schematic diagram , between probes is mounted a switch ( you can use a push-button) for testing the circuit , but it can be removed .
The speaker used in this project must have a impedance between 15 and 90 ohms .

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LM317 based DC motor speed controller with circuit

A very simple DC motor speed controller circuit can be constructed using a LM317 voltage regulator integrated circuit . This DC motor speed controller can be used for speed control of mini drills or for other small DC motors . This motor controller circuit will provide a large output current . The maximum output current from the secondary turns of the transformer shout provide 1.5 times of the maximum DC output current . The output voltage and the speed ( rpm ) is set by the P2 variable resistor .

As soon as the current drawn exceeds a certain value , T2 will be switched on . This results in a base current for T3 so that R5 is in parallel with R6 . This automatically raise the output voltage to counter a threatened drop in rpm . The moment at which this action occurs is set by P1 .

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Thursday, November 6, 2014

Digital Dice With 7 Segment Display

A digital dice circuit can be easily realised using an astable oscillator circuit followed by a counter, display driver and a display. Here we have used a timer NE555 as an astable oscillator with a frequency of about 100 Hz. Decade counter IC CD4026 or CD4033 (which-ever available) can be used as counter-cum-display driver. When using CD4026, pin 14 (cascading output) is to be left unused (open), but in case of CD4033, pin 14 serves as lamp test pin and the same is to be grounded.

Circuit diagram :

Digital Dice With 7-Segment Display Circuit diagram

The circuit uses only a handful of components. Its power consumption is also quite low because of use of CMOS ICs, and hence it is well suited for battery operation. In this circuit two tactile switches S1 and S2 have been pro-vided. While switch S2 is used for initial resetting of the display to ‘0,’ depression of S1 simulates throwing of the dice by a player.

When battery is connected to the circuit, the counter and display section around IC2 (CD4026/4033) is energised and the display would normally show ‘0’, as no clock input is available. Should the display show any other decimal digit, you may press re-set switch S2 so that display shows ‘0’. To simulate throwing of dice, the player has to press switch S1, briefly. This ex-tends the supply to the astable oscillator configured around IC1 as well as capacitor C1 (through resistor R1), which charges to the battery voltage. Thus even after switch S1 is released, the astable circuit around IC1 keeps producing the clock until capacitor C1 discharges sufficiently. Thus for du-ration of depression of switch S1 and discharge of capacitor C1 thereafter, clock pulses are produced by IC1 and applied to clock pin 1 of counter IC2, whose count advances at a frequency of 100 Hz until C1 discharges sufficiently to deactivate IC1.

When the oscillations from IC1 stop, the last (random) count in counter IC2 can be viewed on the 7-segment display. This count would normally lie between 0 and 6, since at the leading edge of every 7th clock pulse, the counter is reset to zero. This is achieved as follows.

Outputs

Observe the behavior of ‘b’ segment output in the Table. On reset, at count 0 until count 4, the segment ‘b’ output is high. At count 5 it changes to low level and remains so during count 6. However, at start of count 7, the output goes from low to high state. A differentiated sharp high pulse through C-R combination of C4-R5 is applied to reset pin 15 of IC2 to reset the output to ‘0’ for a fraction of a pulse period (which is not visible on the 7-segment display). Thus, if the clock stops at seventh count, the display will read zero. There is a probability of one chance in seven that display would show ‘0.’ In such a situation, the concerned player is given an-other chance until the display is non-zero.

Note. Although it is quite feasible to inhibit display of ‘0’ and advance the counter by ‘1,’ the same makes the circuit somewhat complex and there-fore such a modification has not been attempted.

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Tuesday, October 28, 2014

TA8122 bassed AM FM radio receiver Diagram

A very simple low power AM FM radio receiver electronic projects can be designed using the TA8122 integrated AM FM receiver , manufactured by Toshiba Semiconductor . This radio receiver circuit can be used for portable radio applications or other similar devices .

TA8122 radio receiver circuit supports a wide input voltage range from 1.7 volt up to 7 volts , but for this AM FM radio receiver circuit we will need just a 3 volt DC input voltage ( you can use two 1.5 volt Batteries ) .

Using this receiver integrated circuit you can design a very simple AM FM radio receiver or a radio receiver circuit that supports just one of this band (AM or FM) using few additional components .

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Friday, October 17, 2014

12V Powered 12V Lead Acid Battery Charger with Indicator

Some of you might wonder why a charger is needed at all, to charge a 12 Volt battery from a 12 Volt source! Well, firstly the "12 Volt" source will typically vary anywhere from 11 Volt to 15 Volt, and then a battery needs a controlled charge current and voltage, which cannot result from connecting it directly to a voltage source. The charger described here is intended for charging small 12 Volt lead acid batteries, such as the gelled or AGM batteries of capacities between about 2 and 10 Ah, using a cars electrical system as power source, regardless of whether the car engine is running or not. I built this charger many years ago, I think I was still in school back then. On request of a reader of my web site, Im publishing it now, despite being a rather crude circuit.

12V

12V

It works, it is uncritical to build, and uses only easy-to-find parts, so it has something in its favor. The downside is mainly the low efficiency: This charger wastes about as much power as it puts into the battery. The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors connected as emitter followers, which in turn drive the voltage doubler proper. The doubler has power resistors built in, which limit the charging current. The second stage is a voltage regulator, using a 7815 regulator IC. Its output is applied to the battery via a diode, which prevents reverse current and also lowers the voltage a bit.

12V

12V

The resulting charge voltage is about 14.4V, which is fine for charging a gelled or AGM battery to full charge, but is too high as a trickle charger, so dont leave this charger permanently connected to a battery. If you would like to do just that, then add a second diode in series with D3! There is a LED connected as a charge indicator. It will light when the charge current is higher than about 150mA. The maximum charge current will be roughly 400mA. There is an auxiliary output, that provides about 20V at no load (depending on input voltage), and comes down as the load increases. I included this for charging 12V, 4Ah NiCd packs, which require just a limited current but not a limited voltage for charging.

12V

12V

Note that if the charge output is short-circuited, the overcurrent protection of U2 will kick in, but the current is still high enough to damage the diodes, if it lasts. So, dont short the output! If instead you short the auxiliary output, the fuse should blow. I built this charger into a little homemade aluminum sheet enclosure, using dead-bug construction style. Not very tidy, but it works. Note the long leads on the power resistors. They are necessary, because with shorter leads the resistors will unsolder themselves, as they get pretty hot! The transistors and the regulator IC are bolted to the case, which serves as heat sink. The transistors dont heat up very much, but the IC does.

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Thursday, October 9, 2014

Amplifier 250 500W with transistors MJ15003

GENERAL DISCRIPTION :The circuit is based around (TL 071) manufactured by NATIONAL semiconductors (MJ15003) by ON semiconductors It is a high fidelity audio power amplifier. Designed for demanding consumer and pro-audio applications. You can also use this circuit with AV receivers, Audiophile power amps, Pro Audio High voltage industrial applications etc Amplifier output power maybe scaled by changing the supply voltage and number of output devices.

General Specifications
Rated Power Output
(20Hz to 20kHz Continuous Average Sine Wave)
250 watts into 8 ohms
500 watts into 4 ohms
Power Bandwidth
(250 watts into 8 ohms)
20Hz to 40kHz (0dB to -3dB)
Frequency Response
1 watt into 8 ohms
20Hz to 100kHz (0dB to -1.0 dB)
250 watts into 8 ohms
20Hz to 20kHz (Flat)
Input Sensitivity
+3 dBV
(1.4V RMS produces an output of 350 watts into 8 ohms)
Input Impedance
33K ohms, Unbalanced
Rise Time
2.0 microSeconds
Total Harmonic Distortion (THD)
Full Power(250 watts into 8 ohms)
Less than 0.007 % THD @ 1kHz
Less than 0.08 % THD @ 20Hz to 20kHz
Half Power (125 watts into 8 ohms)
Less than 0.003 % THD @ 1kHz
Less than 0.03 % THD @ 20Hz to 20kHz
10 watts into 8 ohms
Less than 0.003 % THD @ 1kHz
Less than 0.01 % THD @ 20Hz to 20kHz

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Wednesday, October 8, 2014

NCP3155 bassed 5 volt regulator circuit project with explanation

This 5 volt regulator circuit project is designed using the NCP3155 DC DC synchronous switching regulator with fully integrated power switches and full fault protection. The switching frequency of 1 MHz and 500 kHz allows the use of small filter components, which results in smaller board space and reduced BOM cost.
This 5 volt regulator circuit project drives high−side and low−side N−channel power MOSFETs. The NCP3155 incorporates an internal boost circuit consisting of a boost clamp and boost diode to provide supply voltage for the high side MOSFET gate driver. This regulator also integrates several protection features including input undervoltage lockout (UVLO), output undervoltage (OUV), output overvoltage (OOV), adjustable high−side
current limit (ISET and ILIM), and thermal shutdown (TSD).

This circuit require few external electronic parts and can be configured very easy . In put voltage that is required by this power supply circuit must be between 10.8 and 24 volts an can provide a fixed output voltage between 1.2 volts up to 5 volts by changing a simple resistor .

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Wednesday, September 24, 2014

Active Bass Enhancer with Correction Circuit for Subwoofers

Active loudspeakers offer the only way f obtaining good bass reproduction from inexpensive or small enclosures.
The design described does not make use, therefore, of large, heavy enclosures to obtaion a good result, but of acoustic feedback. A microphone placed in close proximity of the bass drive unit unfailingly registers every movement of the loud-speaker. It is, of course, important that proper attention is paid to the maximum movement of the speaker.

The microphone output is coupled . into the negative feedback loop ofthe output amplifier. In this way, the input sig- nal to the amplifier is compared with the acoustic signal produced by the speaker. In practice, this arrangement appears to work well only with low-frequency signals. Experiments have shown that if the microphone is placed about 10 mm from the cone of the woofer, signals at e frequencies of up to 500 Hz are fed back faithfully.

To make absolutely certain of correct operation, in the present circuit the upper frequency has been set to 300 Hz; above it, the correcting action gradually ceases. Note, however, that the phase behaviour of the loudspeaker is corrected also for signals above 300 Hz. lf the change-over frequency ofthe cross- over filter ofthe loudspeaker lies at 300 Hz, it is advisable to make the cut-off frequency ofthe present circuit, determined by R6-C8, lower than 300 Hz. The gain of lC2 over the operating range of the circuit is 20 dB, which reduces to 0 dB for frequencies above 300 Hz. This amplifier, which provides the correction up to the cut~off point, also serves as buffer for the microphone signal.

Preset Pl serves to set the signal level on the basis of the power rating of the n outpu amplifier and the efficiency of the microphone. lf this control is set too high, corection is also applied to frequencies above the cut-off point; if it is set too low, little correction will be applied and signals between 20 Hz and 300 Hz will increase along a standard lst order characteristic. The choice of microphone is a matter of some experimentation, particularly with high-power amplifiers.

That used in the proposed subwoofer bass enhancer prototype proved to work well with low-power systems with a relatively low efficiency. If another type is used, make sure that the potential across the microphone is about half the supply voltage. This is arranged by R8 and R9. Also make sure that the cut-off point set by P1-C9 remains well below 20 Hz (no signal at P1 results in an increase of the final amplification). The frequency up to which the microphone signal is compensated is determined by R8-P1-Cm.

This time-constant must be equal to R6-C8. The present circuit can magnify frequencies down to 20 Hz by roughly 20 dB. Since most loudspeakers cannot cope with that frequency, the circuit includes a 3rd order Butterworth section with a cut-off point of 37 Hz.

This frequency may be altered by changing the values of C1, C2, and C3. This filter prevents the loud-speaker being loaded with signals which it cannot reproduce. The bass correction circuit is of particular use with active loud speaker systems.M2 makes sure that the loudspeaker phase is sh ifted by l80° to prevent positive feedback. This may be done by adding an inverter-buffer before K2. The circuit draws about t5 mA, of which only 0.25 mA is drawn by the microphone.

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Tuesday, September 23, 2014

10W Audio Amplifier With Bass Boost circuit and explanation

High Quality, very simple design, No preamplifier required

This design is based on the 18 Watt Audio Amplifier, and was developed mainly to satisfy the requests of correspondents unable to locate the TLE2141C chip. It uses the widespread NE5532 Dual IC but, obviously, its power output will be comprised in the 9.5 – 11.5W range, as the supply rails cannot exceed ±18V. As amplifiers of this kind are frequently used to drive small loudspeaker cabinets, the bass frequency range is rather sacrificed. Therefore a bass-boost control was inserted in the feedback loopof the amplifier, in order to overcome this problem without quality losses. The bass lift curve can reach a maximum of +16.4dB @ 50Hz. In any case, even when the bass control is rotated fully counterclockwise, the amplifier frequency response shows a gentle raising curve: +0.8dB @ 400Hz, +4.7dB @ 100Hz and +6dB @ 50Hz (referred to 1KHz).

Amplifier with Bass-Boost: 10W

10W Bass Boost Amplifier Circuit Diagram

Parts:

P1_________________22K Log.Potentiometer (Dual-gang for stereo)
P2________________100K Log.Potentiometer (Dual-gang for stereo)
R1________________820R 1/4W Resistor
R2,R4,R8____________4K7 1/4W Resistors
R3________________500R 1/2W Trimmer Cermet
R5_________________82K 1/4W Resistor
R6,R7______________47K 1/4W Resistors
R9_________________10R 1/2W Resistor
R10__________________R22 4W Resistor (wirewound)
C1,C8_____________470nF 63V Polyester Capacitor
C2,C5_____________100µF 25V Electrolytic Capacitors
C3,C4_____________470µF 25V Electrolytic Capacitors
C6_________________47pF 63V Ceramic or Polystyrene Capacitor
C7_________________10nF 63V Polyester Capacitor
C9________________100nF 63V Polyester Capacitor
D1______________1N4148 75V 150mA Diode
IC1_____________NE5532 Low noise Dual Op-amp
Q1_______________BC547B 45V 100mA NPN Transistor
Q2_______________BC557B 45V 100mA PNP Transistor
Q3_______________TIP42A 60V 6A PNP Transistor
Q4_______________TIP41A 60V 6A NPN Transistor
J1__________________RCA audio input socket

Power Supply : Power

Power Supply Circuit Diagram

Power supply parts:

R11_________________1K5 1/4W Resistor
C10,C11__________4700µF 25V Electrolytic Capacitors
D2________________100V 4A Diode bridge
D3________________5mm. Red LED
T1________________220V Primary, 12 + 12V Secondary 24-30VA Mains transformer
PL1_______________Male Mains plug
SW1_______________SPST Mains switch

Notes:

Can be directly connected to CD players, tuners and tape recorders.
Schematic shows left channel only, but C3, C4, IC1 and the power supply are common to both channels.
Numbers in parentheses show IC1 right channel pin connections.
A log type for P2 will ensure a more linear regulation of bass-boost.
Do not exceed 18 + 18V supply.
Q3 and Q4 must be mounted on heatsink.
D1 must be in thermal contact with Q1.
Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical.
Set the volume control to the minimum and R3 to its minimum resistance.
Power-on the circuit and adjust R3 to read a current drawing of about 20 to 25mA.
Wait about 15 minutes, watch if the current is varying and readjust if necessary.
A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 &C4. Connect C9 to the output ground.
Then connect separately the input and output grounds to the power supply ground.

Technical data:
Output power:
10 Watt RMS into 8 Ohm (1KHz sinewave)
Sensitivity:
115 to 180mV input for 10W output (depending on P2 control position)
Frequency response:
See Comments above
Total harmonic distortion @ 1KHz:
0.1W 0.009% 1W 0.004% 10W 0.005%
Total harmonic distortion @ 100Hz:
0.1W 0.009% 1W 0.007% 10W 0.012%
Total harmonic distortion @ 10KHz:
0.1W 0.056% 1W 0.01% 10W 0.018%
Total harmonic distortion @ 100Hz and full boost:
1W 0.015% 10W 0.03%
Max. bass-boost referred to 1KHz:
400Hz = +5dB; 200Hz = +7.3dB; 100Hz = +12dB; 50Hz = +16.4dB; 30Hz = +13.3dB
Unconditionally stable on capacitive loads

Elektor 303 Circuit

Practical Arduino

Elektor05-2010

Elektor05-2010

Elektor05-2010

Nuts Volts 06-2010

Nuts Volts 06-2010

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Friday, September 19, 2014

12V Powered 12V Lead Acid Battery Charger with Indicator

Some of you might wonder why a charger is needed at all, to charge a 12 Volt battery from a 12 Volt source! Well, firstly the "12 Volt" source will typically vary anywhere from 11 Volt to 15 Volt, and then a battery needs a controlled charge current and voltage, which cannot result from connecting it directly to a voltage source. The charger described here is intended for charging small 12 Volt lead acid batteries, such as the gelled or AGM batteries of capacities between about 2 and 10 Ah, using a cars electrical system as power source, regardless of whether the car engine is running or not. I built this charger many years ago, I think I was still in school back then. On request of a reader of my web site, Im publishing it now, despite being a rather crude schema.

12V

12V

It works, it is uncritical to build, and uses only easy-to-find parts, so it has something in its favor. The downside is mainly the low efficiency: This charger wastes about as much power as it puts into the battery. The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors connected as emitter followers, which in turn drive the voltage doubler proper. The doubler has power resistors built in, which limit the charging current. The second stage is a voltage regulator, using a 7815 regulator IC. Its output is applied to the battery via a diode, which prevents reverse current and also lowers the voltage a bit.

12V

12V

The resulting charge voltage is about 14.4V, which is fine for charging a gelled or AGM battery to full charge, but is too high as a trickle charger, so dont leave this charger permanently connected to a battery. If you would like to do just that, then add a second diode in series with D3! There is a LED connected as a charge indicator. It will light when the charge current is higher than about 150mA. The maximum charge current will be roughly 400mA. There is an auxiliary output, that provides about 20V at no load (depending on input voltage), and comes down as the load increases. I included this for charging 12V, 4Ah NiCd packs, which require just a limited current but not a limited voltage for charging.

12V

12V

Note that if the charge output is short-schemaed, the overcurrent protection of U2 will kick in, but the current is still high enough to damage the diodes, if it lasts. So, dont short the output! If instead you short the auxiliary output, the fuse should blow. I built this charger into a little homemade aluminum sheet enclosure, using dead-bug construction style. Not very tidy, but it works. Note the long leads on the power resistors. They are necessary, because with shorter leads the resistors will unsolder themselves, as they get pretty hot! The transistors and the regulator IC are bolted to the case, which serves as heat sink. The transistors dont heat up very much, but the IC does.

Source: Homo Ludens

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Monday, September 15, 2014

Mixed acoustic connection to an amplifier with two bridge output channels

Consider the circuit connection to the AC amplifier with two bridge output channels. Dynamic head BA1, BA2 speakers form the left and right stereo channels. They are shown conventionally broadband. Low-frequency head BA3 is connected between the output of the amplifier left and right channels, the signals are summed and head reproduces a mono signal.

This connection will be sure to have two high-pass and low-pass filter for the stereo for the total channel. Their mission - to eliminate the parallel operation and overload amplifier heads. Usually used for stereo first order filters (C1, C2), for the total - the second (C3L1) or third.Their payment is made in the usual way. Crossover frequency of the LPF and the order chosen in the range 80 ... 200 Hz, depending on the location of the low-frequency head. If it is placed in the rear compartment, the crossover frequency should be selected as low as possible, and the order - up to avoid reproducing the subwoofer "voice" of the range. However, this requires the manufacture of relatively large inductors.Used in their construction ferromagnetic yokes undesirable because the distortion caused by the inevitable core magnetization significantly degrade sound quality.

Original article sourse cxem.net

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Friday, September 12, 2014

5W AUDIO AMPLIFIER WITH MUTING

Circuit Diagram for 5W AUDIO AMPLIFIER WITH MUTING

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Thursday, September 11, 2014

Subwoofer amplifier with 30W output power

hifi

Amplifier circuit is very suitable for use in subwoofer amplifier system based on IC SI1030G. Amplfier has 30W output with 8 ohm impedance. Supply voltage required minimum of 12 volts and a maximum of up to 22 volts DC.

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Tuesday, September 9, 2014

30 VDC Stabilized power supply with current control 0 002 3 A

General Description

This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC. The schema also incorporates an electronic output current limiter that effectively controls the output current from a few milliamperes (2 mA) to the maximum output of three amperes that the schema can deliver. This feature makes this power supply indispensable in the experimenters laboratory as it is possible to limit the current to the typical maximum that a schema under test may require, and power it up then, without any fear that it may be damaged if something goes wrong.

There is also a visual indication that the current limiter is in operation so that you can see at a glance that your schema is exceeding or not its preset limits.Link

Technical Specifications - Characteristics

Input Voltage: ................ 24 VAC
Input Current: ................ 3 A (max)
Output Voltage: ............. 0-30 V adjustable
Output Current: ............. 2 mA-3 A adjustable
Output Voltage Ripple: . 0.01 % maximum

FEATURES
- Reduced dimensions, easy construction, simple operation.
- Output voltage easily adjustable.
- Output current limiting with visual indication.
- Complete protection of the supplied device against over loads and malfunction.

How it Works

To start with, there is a step-down mains transformer with a secondary winding rated at 24 V/3 A, which is connected across the input points of the schema at pins 1 & 2. (the quality of the supplies output will be directly proportional to the quality of the transformer). The AC voltage of the transformers secondary winding is rectified by the bridge formed by the four diodes D1-D4. The DC voltage taken across the output of the bridge is smoothed by the filter formed by the reservoir capacitor C1 and the resistor R1. The schema incorporates some unique features which make it quite different from other power supplies of its class. Instead of using a variable feedback arrangement to control the output voltage, our schema uses a constant gain amplifier to provide the reference voltage necessary for its stable operation. The reference voltage is generated at the output of U1. The schema operates as follows: The diode D8 is a 5.6 V zener, which here operates at its zero temperature coefficient current. The voltage in the output of U1 gradually increases till the diode D8 is turned on. When this happens the schema stabilises and the Zener reference voltage (5.6 V) appears across the resistor R5. The current which flows through the non inverting input of the op-amp is negligible, therefore the same current flows through R5 and R6, and as the two resistors have the same value the voltage across the two of them in series will be exactly twice the voltage across each one. Thus the voltage present at the output of the op-amp (pin 6 of U1) is 11.2 V, twice the zeners reference voltage. The integrated schema U2 has a constant amplification factor of approximately 3 X, according to the formula A=(R11+R12)/R11, and raises the 11.2 V reference voltage to approximately 33 V. The trimmer RV1 and the resistor R10 are used for the adjustment of the output voltages limits so that it can be reduced to 0 V, despite any value tolerances of the other components in the schema. Another very important feature of the schema, is the possibility to preset the maximum output current which can be drawn from the p.s.u., effectively converting it from a constant voltage source to a constant current one. To make this possible the schema detects the voltage drop across a resistor (R7) which is connected in series with the load. The IC responsible for this function of the schema is U3. The inverting input of U3 is biased at 0 V via R21. At the same time the non inverting input of the same IC can be adjusted to any voltage by means of P2. Let us assume that for a given output of several volts, P2 is set so that the input of the IC is kept at 1 V. If the load is increased the output voltage will be kept constant by the voltage amplifier section of the schema and the presence of R7 in series with the output will have a negligible effect because of its low value and because of its location outside the feedback loop of the voltage control schema. While the load is kept constant and the output voltage is not changed the schema is stable. If the load is increased so that the voltage drop across R7 is greater than 1 V, IC3 is forced into action and the schema is shifted into the constant current mode. The output of U3 is coupled to the non inverting input of U2 by D9. U2 is responsible for the voltage control and as U3 is coupled to its input the latter can effectively override its function. What happens is that the voltage across R7 is monitored and is not allowed to increase above the preset value (1 V in our example) by reducing the output voltage of the schema. This is in effect a means of maintaining the output current constant and is so accurate that it is possible to preset the current limit to as low as 2 mA. The capacitor C8 is there to increase the stability of the schema. Q3 is used to drive the LED whenever the current limiter is activated in order to provide a visual indication of the limiters operation. In order to make it possible for U2 to control the output voltage down to 0 V, it is necessary to provide a negative supply rail and this is done by means of the schema around C2 & C3. The same negative supply is also used for U3. As U1 is working under fixed conditions it can be run from the unregulated positive supply rail and the earth. The negative supply rail is produced by a simple voltage pump schema which is stabilised by means of R3 and D7. In order to avoid uncontrolled situations at shut-down there is a protection schema built around Q1. As soon as the negative supply rail collapses Q1 removes all drive to the output stage. This in effect brings the output voltage to zero as soon as the AC is removed protecting the schema and the appliances connected to its output. During normal operation Q1 is kept off by means of R14 but when the negative supply rail collapses the transistor is turned on and brings the output of U2 low. The IC has internal protection and can not be damaged because of this effective short schemaing of its output. It is a great advantage in experimental work to be able to kill the output of a power supply without having to wait for the capacitors to discharge and there is also an added protection because the output of many stabilised power supplies tends to rise instantaneously at switch off with disastrous results.

Construction

First of all let us consider a few basics in building electronic diagram on a printed schema 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 schema. The use of a properly designed printed schema board is very desirable as it speeds construction up considerably and reduces the possibility of making errors. 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 schema 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 schema 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 components body and insert he 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 allow 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-schemaing 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.

(17,8KB)	(12,5cm x 8,7cm)
layout

As it is recommended start working by identifying the components and separating them in groups. Place first of all the sockets for the ICs and the pins for the external connections and solder them in their places. Continue with the resistors. Remember to mound R7 at a certain distance from the printed schema board as it tends to become quite hot, especially when the schema is supplying heavy currents, and this could possibly damage the board. It is also advisable to mount R1 at a certain distance from the surface of the PCB as well. Continue with the capacitors observing the polarity of the electrolytic and finally solder in place the diodes and the transistors taking care not to overheat them and being at the same time very careful to align them correctly.

Mount the power transistor on the heatsink. To do this follow the diagram and remember to use the mica insulator between the transistor body and the heatsink and the special fibber washers to insulate the screws from the heatsink. Remember to place the soldering tag on one of the screws from the side of the transistor body, this is going to be used as the collector lead of the transistor. Use a little amount of Heat Transfer Compound between the transistor and the heatsink to ensure the maximum transfer of heat between them, and tighten the screws as far as they will go.

Attach a piece of insulated wire to each lead taking care to make very good joints as the current that flows in this part of the schema is quite heavy, especially between the emitter and the collector of the transistor.

It is convenient to know where you are going to place every thing inside the case that is going to accommodate your power supply, in order to calculate the length of the wires to use between the PCB and the potentiometers, the power transistor and for the input and output connections to the schema. (It does not really matter if the wires are longer but it makes a much neater project if the wires are trimmed at exactly the length necessary).

Connect the potentiometers, the LED and the power transistor and attach two pairs of leads for the input and output connections. Make sure that you follow the schema diagram very care fully for these connections as there are 15 external connections to the schema in total and if you make a mistake it may be very difficult to find it afterwards. It is a good idea to use cables of different colours in order to make trouble shooting easier.
The external connections are:
- 1 & 2 AC input, the secondary of the transformer.
- 3 (+) & 4 (-) DC output.
- 5, 10 & 12 to P1.
- 6, 11 & 13 to P2.
- 7 (E), 8 (B), 9 (E) to the power transistor Q4.
- The LED should also be placed on the front panel of the case where it is always visible but the pins where it is connected at are not numbered.

When all the external connections have been finished make a very careful inspection of the board and clean it to remove soldering flux residues. Make sure that there are no bridges that may short schema adjacent tracks and if everything seems to be all right connect the input of the schema with the secondary of a suitable mains transformer. Connect a voltmeter across the output of the schema and the primary of the transformer to the mains.
DO NOT TOUCH ANY PART OF THE CIRCUIT WHILE IT IS UNDER POWER.
The voltmeter should measure a voltage between 0 and 30 VDC depending on the setting of P1, and should follow any changes of this setting to indicate that the variable voltage control is working properly. Turning P2 counter-clockwise should turn the LED on, indicating that the current limiter is in operation.

Adjustments

If you want the output of your supply to be adjustable between 0 and 30 V you should adjust RV1 to make sure that when P1 is at its minimum setting the output of the supply is exactly 0 V. As it is not possible to measure very small values with a conventional panel meter it is better to use a digital meter for this adjustment, and to set it at a very low scale to increase its sensitivity.

Warning

While using electrical parts, handle power supply and equipment with great care, following safety standards as described by international specs and regulations.
CAUTION
This schema works off the mains and there are 220 VAC present in some of its parts.
Voltages above 50 V are DANGEROUS and could even be LETHAL.
In order to avoid accidents that could be fatal to you or members of your family please observe the following rules:
- DO NOT work if you are tired or in a hurry, double check every thing before connecting your schema to the mains and be ready
- to disconnect it if something looks wrong.
- DO NOT touch any part of the schema when it is under power.
- DO NOT leave mains leads exposed. All mains leads should be well insulated.
- DO NOT change the fuses with others of higher rating or replace them with wire or aluminium foil.
- DO NOT work with wet hands.
- If you are wearing a chain, necklace or anything that may be hanging and touch an exposed part of the schema BE CAREFUL.
- ALWAYS use a proper mains lead with the correct plug and earth your schema properly.
- If the case of your project is made of metal make sure that it is properly earthen.
- If it is possible use a mains transformer with a 1:1 ratio to isolate your schema from the mains.
- When you are testing a schema that works off the mains wear shoes with rubber soles, stand on dry non conductive floor
- and keep one hand in your pocket or behind your back.

- If you take all the above precautions you are reducing the
- risks you are taking to a minimum and this way you are protecting
- yourself and those around you.
- A carefully built and well insulated device does not constitute any danger for its user.
- BEWARE: ELECTRICITY CAN KILL IF YOU ARE NOT CAREFUL.

If it does not work

Check your work for possible dry joints, bridges across adjacent tracks or soldering flux residues that usually cause problems.
Check again all the external connections to and from the schema to see if there is a mistake there.
- See that there are no components missing or inserted in the wrong places.
- Make sure that all the polarised components have been soldered the right way round. - Make sure the supply has the correct voltage and is connected the right way round to your schema.
- Check your project for faulty or damaged components.

Electronic Diagram.

Parts List.

R1 = 2,2 KOhm 1W

R2 = 82 Ohm 1/4W

R3 = 220 Ohm 1/4W

R4 = 4,7 KOhm 1/4W

R5, R6, R13, R20, R21 = 10 KOhm 1/4W

R7 = 0,47 Ohm 5W

R8, R11 = 27 KOhm 1/4W

R9, R19 = 2,2 KOhm 1/4W

R10 = 270 KOhm 1/4W

R12, R18 = 56KOhm 1/4W

R14 = 1,5 KOhm 1/4W

R15, R16 = 1 KOhm 1/4W

R17 = 33 Ohm 1/4W

R22 = 3,9 KOhm 1/4W

RV1 = 100K trimmer

P1, P2 = 10KOhm linear pontesiometer

C1 = 3300 uF/50V electrolytic

C2, C3 = 47uF/50V electrolytic

C4 = 100nF polyester

C5 = 200nF polyester

C6 = 100pF ceramic

C7 = 10uF/50V electrolytic

C8 = 330pF ceramic

C9 = 100pF ceramic

D1, D2, D3, D4 = 1N5402,3,4 diode 2A - RAX GI837U

D5, D6 = 1N4148

D7, D8 = 5,6V Zener

D9, D10 = 1N4148

D11 = 1N4001 diode 1A

Q1 = BC548, NPN transistor or BC547

Q2 = 2N2219 NPN transistor

Q3 = BC557, PNP transistor or BC327

Q4 = 2N3055 NPN power transistor

U1, U2, U3 = TL081, operational amplifier

D12 = LED diode

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Sunday, September 7, 2014

Schematic Audio Amplifier with IC A211D TBA611

See this circuit below:

Datasheet IC A211D

Vcc = 4,5-15 V

Pout = 1 W

RL = 8 Ohm

Ft = 50-15 Khz

Icco = 10 mA

Package = TABS4-14

Manufactered = RFT

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Call Bell with Welcome Indication

Call Bell with Welcome Indication Circuit Diagram. Here is a simple call bell schema that displays a welcome message when somebody presses the call bell switch momentarily. the alphanumeric display can be fitted near the call bell switch. the schema is built around two 555 ICs (IC1 and IC2), seven KLA511 common-anode alphanumeric displays (DIS1 through DIS7) and a few discrete components. For easy understanding, the entire schema can be divided into two sections: controller and display. the controller section is built around IC1 and IC2, while the display section is built around alphanumeric displays (DIS1 through DIS7).

As shown in the schema, both IC1 and IC2 are wired as monostable multivibrators having time periods of around 5 seconds and 2 minutes, respectively. You can change the time period of IC1 by changing the values of resistor R12 and capacitor C3. Similarly, the time period of IC2 can be changed by changing the values of resistor R2 and capacitor C1. Alphanumeric displays DIS1 through DIS7 are wired such that they show ‘WELCOME’ when the output of IC2 goes high. the schema is powered by a 6V battery. Else, you can use the 6V, 300mA power adaptor that is readily available in the market. the 6V battery or power adaptor provides regulated 6V required to operate the schema.

Call Bell with Welcome Indication Circuit Diagram :

Call Bell with Welcome Indication Circuit Diagram

A 6V DC socket is used in the schema to connect the output of the adaptor if you don’t use the battery. Working of the schema is simple. First, power-on the schema using switch S2. LED1 glows to indicate presence of power supply in the schema. Now if you press call bell switch S1 momentarily, it triggers both the timers (IC1 and IC2) simultaneously. IC1 produces a high output at its pin 3 for about five seconds. transistor t2 conducts and piezobuzzer PZ1 sounds for about five seconds indicating that there is somebody at the door. At the same time, IC2 too produces a high out-put at its pin 3 for about two minutes. transistor t1 conducts to enable the alphanumeric displays. the word ‘WEL-COME’ is displayed for about two minutes as DIS1 through DIS7 ground via transistor T1.

If switch S1 is pressed again within these two minutes, piezobuzzer PZ1 again sounds for five seconds and the display continues to show ‘WEL-COME’. Assemble the complete schema on a general purpose PCB and house in a small cabinet with call bell switch S1 and LED1 mounted on the front panel. At the rear side of the cabinet, connect a DC socket for the adaptor. Install the complete unit (along with the display) at the entrance of your house. Connect the 6V battery or 6V adaptor for powering the schema. Configure switch 2 (used to enable/disable the call bell) in a switch board at a suitable location inside your house. If you don’t use a battery, connect the power adaptor to the DC socket on the rear of the cabinet. Close switch S2 only when you want to activate the schema with battery. Otherwise, keep it open when the 6V adaptor is in use.

EFY note.

1. To avoid any shorting during rain, waterproof the entire schema assembly including alphanumeric displays (installed at the entrance) by covering it properly.

2. the complete kit for this schema is available with EFY associates kits’n’spares.

Author : S.C. Dwivedi - Copyright : EFY

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Monday, September 1, 2014

20W amplifier schematic with mute

This is a series of audio amplifier using ic and equipped with a mute switch. This circuit using ic and has 20W output impedance 4 ohms. Scheme and a list of components can be seen below.

20W

Read more

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Friday, June 6, 2014

An LCD Clock Kit Suitable for Beginners with Open Source Arduino Firmware

Simpleclock is an easy to assemble attractive 4-digit 7-segment LED display clock with temperature and alarm function. It is available in three display colors: Red, Blue and White. It comes as a kit of through-the-hole parts and can be soldered by any person with basic soldering experience. An attractive acrylic stand is included. [Link]

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Making A Self Watering Plant with Arduino

Plants liven up any space by adding a sense of airiness and life. That is – of course – when you don’t forget to water them, and they shrivel up and die. I am very bad at remembering to water plants. That is why I built this self-watering plant to do it for me. Using a soil sensor, and an Arduino-controlled water pump, I have created a system that will never forget to do it.

Making A Self-Watering Plant with Arduino

Instead of remembering to water my plants when the soil goes dry, I only have to remember to once and a while refill the water reservoir. In this way, I have decreased my obligation to these plants and put it off to a much later date. Perhaps further iterations of this device can be connected to a rain barrel so that I won’t even have to worry about refilling my reservoir, and the entire system can be fully automated. [Link]

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