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Friday, December 27, 2013

Simple Tone Control by using Discrete Components

Simple Tone Control specifically designed for the 3 - 5 Watt Class-A audio amplifiers. Traditional Bass, Treble Controls and DC 24V power supply. A Bass and Treble frequency control to be added to the 3 - 5W Class-A Amplifier was required by some audio enthusiasts. Therefore, this circuit has been designed keeping in mind the extreme simplicity of the amplifier circuit to which it should be linked and was carried out using as few as components possible.
Simple Tone Control Circuit Diagram
Simple Tone Control Circuit Diagram

Parts


P1______________47K Log. Potentiometer (See Notes)
P2,P3___________47K Linear Potentiometers
R1,R3,R5_________4K7 1/4W Resistors
R2______________22K 1/4W Resistor
R4_______________1M 1/4W Resistor
R6_______________1K8 1/4W Resistor
R7_____________560R 1/4W Resistor
C1,C4,C5,C7_____10µF 63V Electrolytic Capacitors (See Notes)
C2______________47nF 63V Polyester Capacitor
C3_______________1nF 63V Polyester Capacitor (See Notes)
C6_____________220µF 35V Electrolytic Capacitor
Q1____________BC550 45V 100mA NPN Low noise High gain NPN Transistor

Q1 is the only active component forming a straightforward single-stage transistor amplifier with the tone control network in the ac feedback path. Taking this feedback from the split load of Q1 we obtain an ac stage gain of about 3: this can be useful to cope with low output voltage audio sources.

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5 LED VU meter circuit diagram using KA2284

This is a simple circuit diagram of 5-LED audio VU meter using IC KA2284/KA2285. The KA2284, KA2285 are monolithic integrated circuit. It is a logarithmic display driver IC. And it is Bar type display driver using 5-Dot LED. The KA2284/KA2285 has a wide range supply voltage capacity of 3.5V-16V, but we recommend to use about a 12VDC power supply.

Circuit Diagram:


KA2284-led vu meter
Fig: 5-LED Dot/Bar (VU meter) circuit diagram

Usability of this circuit:

  • AC signal Meter or DC Level meter.
  • Audio VU(Volume Unit) meter in amplifier or such kind of device.
Here IC AN6884 is also can be used instead of KA2284,KA2285. These all are almost same.
Further reading: DOT vs BAR
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Thursday, December 26, 2013

Reanimating Probe for AVR μC

AVR device not responding, When this discouraging message appears while you’re programming your Atmel microcontroller, that’s where the problems really begin! The problem is of ten due to incorrect programming of the fuse bits. This is where the unblocking probe comes into play.

circuitwe 
Once the whole thing is powered up, all you have to is use one hand to apply the tip of the probe to the microcontroller’s XTAL1 input and then use your other hand to go ahead and program it with your favourite sof t ware. And there, your microcontroller is saved! The electronics are as simple as can be, the aim being to design something cheap and easy to reproduce. It consists of an oscillator generating a rectangular wave at around 500 kHz, built using  a 74HC04. This circuit will also work with a 74HC14, but depending on the make of IC, the frequency of around 500 kHz may vary by around ±50 kHz. This doesn’t affect the operation of the probe.

Reanimating Probe for AVR μC Circuit diagram :
circuit diagram123w
The unblocking board is connected using a ribbon cable, terminated with two female HE10/10 connectors. The pinout of the HE10/10 connector is the same as used in the majority of circuits, but of course it can be adapted for an HE10/06 connector.

The first connector is connected to the board to be unblocked, which allows powering of the electronics. The second connector is connected to the ISP programmer (STK200 compatible). The contact at the crystal is made using a needle, to ensure contact even through a board that has been varnished. There’s no need to unsolder the crystal for this operation.

The PCB design in Eagle format is available from : www.elektor.com

Author : P. Rondane - Copyright : elektor

Source  :http://www.ecircuitslab.com/2012/08/reanimating-probe-for-avr-c.html
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Triangular Wave Oscillator

This design resulted from the need for a partial replacement of the well-known 8038 chip,  which is no longer in production and there fore hardly obtainable.

An existing design for driving an LVDT sensor (Linear Variable Differential Transformer),  where the 8038 was used as a variable sine  wave oscillator, had to be modernised. It may  have been possible to replace the 8038 with an  Exar 2206, except that this chip couldn’t be used  with the supply voltage used. For this reason we  looked for a replacement using standard components, which should always be available.

Triangular Wave Oscillator Circuit diagram:
Triangular Wave Oscillator-Circuit Diagram

In this circuit two opamps from a TL074 (IC1.A  and B) are used to generate a triangular wave,  which can be set to a wide range of frequencies using P1. The following differential amplifier using T1 and T2 is configured in such a way  that the triangular waveform is converted into  a reasonably looking sinusoidal waveform. P2  is used to adjust the distortion to a minimum.

The third opamp (IC1.C) is configured as a  difference amplifier, which presents the sine  wave at its output. This signal is then buffered by the last opamp (IC1.D). Any offset at the  output can be nulled using P3.

Author : Jac Hettema - Copyright : Elektor

Source : http://www.ecircuitslab.com/2012/06/triangular-wave-oscillator.html
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Wednesday, December 25, 2013

DIY Infrared Radar System

Chris from PyroElectro.com has a great article about a do-it-yourself radar system build with PIC18F452. It’s a great hobby project although the schematic is very complicated. This project uses three main devices to create the personal radar system. The IR Range sensor gives output, the pic microcontroller processes it and then displays the output on the led array.

DIY Infrared Radar Circuit Schematic
Circuit Project: DIY Infrared Radar System
The goal of this project is to create a working ir radar system. The system will only be required to measure close proximity at an angle of 90 degrees as seen in the example above. The range of system is roughly 4-30cm, 20-150cm & 1m-5.5m depending upon which sensor you choose to use. [Link]
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Telephone Conversation recorder

This circuit enables  automatic switching-on  of  the  tape  recorder  when  the  handset  is  lifted.  The tape recorder gets switched off when the handset is replaced. The signals are suit-ably  attenuated  to  a  level  at  which  they can be recorded using the MICIN socket of the tape recorder. Points X and Y in the circuit are connected to the telephone lines. Resistors R1 and R2 act as a voltage divider.

The voltage appearing across R2 is fed to the MIC-IN socket of the tape recorder. The values of R1 and R2 may be changed depending on the input impedance of the tape recorders MIC-IN  terminals.  Capacitor C1 is used for blocking the flow of DC. The second part of the circuit controls relay RL1, which is used to switch on/off the tape recorder.A  voltage  of  48  volts  appears across  the  telephone  lines  in on-hook  condition. This  voltage drops  to  about  9  volts  when  the handset  is  lifted.  Diodes  D1 through  D4  constitute  a  bridge rectifier/polarity  guard. 

Telephone Conversation recorder Circuit Diagram
Telephone Conversation recorder Circuit Diagram

This ensures that transistor T1 gets voltage of proper polarity, irrespective of the polarity of the telephone lines.During on-hook condition, the output from the bridge (48V DC) passes through 12V zener D5 and is applied to the base of transistor T1 via the voltage divider comprising resistors R3 and R4. This switches on transistor T1 and its collector is pulled low. This, in turn, causes transistor T2 to cut off and relay RL1 is not energised. When the telephone handset is lifted, the voltage across points X and Y falls below 12 volts and so zener diode D5 does not conduct.

As a result, base of transistor  T1  is  pulled  to  ground  potential  via resistor R4 and thus is cut off. Thus, base of  transistor  T2  gets  forward  biased  via resistor R5, which results in the energisation  of  relay  RL1. The  tape  recorder  is switched on and recording begins. The tape recorder should be kept loaded with a cassette and the record button of the tape recorder should remain pressed to enable it to record  the conversation as soon as the handset is lifted. Capacitor  C2  ensures  that  the  re-lay is not switched on-and-off repeatedly when a number is being dialled in pulse dialling mode.

Source: http://www.ecircuitslab.com/2011/10/telephone-conversation-recorder.html






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Tuesday, December 24, 2013

LED Scanner

Here is a simple LED chaser simulating a scanner through the back and forth light effect. It used high bright White LEDs to give the chaser effect. The circuit uses an oscillator to produce fast pulses and a decade counter to drive the LEDs.

IC1 is designed as an astable multivibrator to give continuous positive pulses to the decade counter. Variable resistor VR1, R1 and C1 form the timing components. By adjusting VR1, it is possible to change the speed of the scanning LEDs.

Output pulses from IC1 are fed to the clock input of the decade counter IC2. Resistor R2 keeps the clock input of IC2 low after each positive to negative transitions of input pulses. This is necessary because sometimes the clock input of the decade counter stays positive and does not accept input pulses.

LED Scanner Circuit

Circuit Project: LED Scanner circuit

All the ten outputs are used in the circuit to drive the LEDs. Diodes D1 through D10 (IN 4148) do the trick of forward and backward chasing effect. Out of the ten diodes, eight diodes form OR gates to direct the outputs of IC2 to LEDs. The remaining two diodes maintain the brightness of the two ungated LEDs. First six outputs of IC2 works in the straight way to give the running effect.

The diode connected to the pin 5 of IC2 is connected to the cathode of the diode from pin 10 (5th LED). This reverses the running sequence in the backward direction. Output 6 drives the 4th LED and the process repeats up to the 2nd LED connected to output pin2.The reset pin 15 and the Clock inhibit pin 13 of IC2 are connected to ground so that IC2 can run freely.
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Universal Tester for 3 pin Devices

Most 3-terminal active components can be  tested statically using just an ohmmeter. But  when you have a lot of these devices to test,  the procedure soon becomes boring. That’s  where the idea came from to combine fast,  easy testing for these types of device into a  single instrument.

The unit described here enables you to test  NPN and PNP bipolar transistors, N-or Pchannel FETs or MOSFETs, UJTs, triacs, and thyristors. Regardless of the type of device, the  tests are non-destructive. Universal connectors allow testing of all package types, including SMDs (up to a point). The unit lets you  change from one type of device to another in  a trice. It avoids using a multi-pole switch, as  they’re too expensive and hard to find.

Universal Tester for 3-pin Devices Circuit diagram:
Universal Tester for 3-pin Devices-Circuit Diagram

Here’s how to build a versatile instrument at  a ridiculously low cost. IC1 is a 4066 quad CMOS switch which will let us switch between bipolar transistors and FETs. LEDs D1–D4 tell us about the condition  of the test device, when we press the ‘Test’  button. The 4066 can only handle a few milliamps, not  enough for the other component types to be  tested, hence the reason for using relay RE1.  This 12 V relay offers two NO contacts. The  first applies power to the UJT test circuit, the  second applies it to the triac and thyristor test  circuit.

Extensive testing has shown that the best way  to test UJT transistors is to do so dynamically,  with the help of a relaxation oscillator. Net-work R11/C1 sets the oscillator frequency to  around 2 Hz. On pin B1 of the UJT we find a  nice sawtooth, which is not of much interest  to us here. However, pin B2 gives good but  very short pulses. IC2, wired as a monostable,  lengthens these pulses so they can be clearly  seen via LED D5.

The relay’s second pole is going to drive the  thyristor’ sortriac’s trigger pin. The value of  R18 is a good compromise with respect to the varying trigger currents for this type of  device. Resistor R17 is important, as the hold-ing current must be high enough for a triac;  250 mA is a good compromise. LED D6 tells  you if the device is in good condition or not;  but watch out, the test result must be con-firmed by briefly cutting the power in order  to reset the triac.

On the web page for this article [1] you’ll find  the author’s CAD files (PCB layout and front  panel) along with some photos of his project.  On the prototype, the LEDs and the ‘Test’  button were wired onto the copper side of  the PCB. The six female connectors for the  devices being tested were salvaged, but there  are lots of models available on the market (the  pitch is standard). The test cable crocodile  clips must be as small as possible for testing  SMD devices.

Source : http://www.ecircuitslab.com/2012/05/universal-tester-for-3-pin-devices.html
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Monday, December 23, 2013

3 Rail Power supply Circuit Diagram

This 3- Rail Power supply Circuit Diagram generates three supply voltages using a minimum of components. Diodes D2 and D3 perform full-wave rectification, alternately charging capacitor C2 on both halves of the ac cycle. On the other hand, diode D1 with capacitor C1, and diode D4 with capacitor C3 each perform half-wave rectification. 

The full-and half-wave rectification arrangement is satisfactory for modest supply currents drawn from -5 and +12-V regulators IC3 and IC2. You can use this circuit as an auxiliary supply in an up-based instrument, for example, and avoid the less attractive alternatives of buying a custom-wound transformer, building a more complex supply, or using a secondary winding, say 18 Vac, and wasting power in the 5-V regulators.

3- Rail Power supply Circuit Diagram

3- Rail Power supply Circuit Diagram

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12KV High Voltage Generator

The hobby circuit below uses an unusual method to generate about 12,000 volts with about 5uA of current. Two SCRs form two pulse generator circuits. The two SCRs discharge a 0.047uF a 400v capacitor through a xenon lamp trigger coil at 120 times a second. The high voltage pulses produced at the secondary of the trigger coil are rectified using two 6KV damper diodes.

Circuit Project:12KV High Voltage Generator

The voltage doubler circuit at the secondary of the trigger coil charges up two high voltage disc capacitors up to about 12KV. Although this circuit can’t produce a lot of current be very careful with it. A 12KV spark can jump about 0.75 of an inch so the electronic circuit needs to be carefully wired with lots of space between components.
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Sunday, December 22, 2013

Easy Dc To Dc Converter Circuit Diagram

This Easy Dc To Dc Converter Circuit Diagram uses a Linear Technology LT1073 in a -24-V converter. The supply can be two AA cells (3 V) or 5 V. The circuit can deliver 7 mA.


Dc To Dc Converter Circuit Diagram

Easy Dc To Dc Converter Circuit Diagram

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1000 watt power inverter circuit diagram

This 1000 watt power inverter circuit diagram based on MOSFET RF50N06.If you want more power then  add additional  MOSFET paralleled at RF50N06.This MOSFETS are  60 Volts and 50 Amps as rated.  It is necessary to connect  a  FUSE with the power line and always a LOAD have to connected while power is being  applied . The output power of this inverter is up-to 1k watt , it depends on output power transformer . You can use your custom transformer with experimenting for best result.

Circuit Diagram | 1000 watt power inverter


1000w inverter circuit
Fig:Schematic diagram of 1000 watt power inverter

How to parallel MOSFETs | 1000 watt power inverter


parallel MOSFETs


Source: http://www3.telus.net/chemelec/Projects/Inverter/Mosfet-Inverter.htm
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Saturday, December 21, 2013

Build A Synchronous Clock

The quartz clocks which have dominated time-keeping for the past 20 years or so have one problem: their errors, although slight, are cumulative. After running for several months the errors can be significant. Sometimes you can correct these if you can slightly tweak the crystal frequency but otherwise you are forced to reset the clock at regular intervals. By contrast, mains-powered synchronous clocks are kept accurate by the 50Hz mains distribution system and they are very reliable, except of course, when a blackout occurs. This circuit converts a quartz clock to synchronous mains operation, so that you can have at least one clock in your home which shows the time. First, you need to obtain a quartz clock movement and disassemble it down to the PC board. For instructions on how to do this, see the article on a "Fast Clock For Railway Modellers" in the December 1996 issue of SILICON CHIP. Then isolate the two wires to the clock coil and solder two light duty insulated hookup wires to them (eg, two strands of rainbow cable). Drill a small hole in the clock case and pass the wires through them. Then reassemble the clock case.

Circuit diagram:

building_a_synchronous_clock circuit

A Synchronous Clock Circuit Diagram

To test the movement, touch the wires to the terminals of an AA cell, then reverse the wires and touch the cell terminals again. The clock second hand should advance on each connection. The circuit is driven by a low voltage AC plug pack. Its AC output is fed to two bridge rectifiers: BR1 provides the DC supply while BR2 provides positive-going pulses at 100Hz to IC1a, a 4093 NAND Schmitt trigger. IC1a squares up the 100Hz pulses and feeds them to the clock input of the cascaded 4017 decade counters. The output at pin 12 of IC3 is 1Hz. This is fed to IC4, a 4013 D-type flipflop, which is connected so that its two outputs at pins 12 & 13 each go positive for one second at a time. As these pulses are too long to drive the clock movement directly, the outputs are each fed to 4093 NAND gates IC1b & IC1c where they are gated with the pin 3 signal to IC4. This results in short pulses from pins 3 & 10 of IC1 which drives the clock via limiting resistor R1. The value of R1 should be selected on test, allowing just enough current to reliably drive the clock movement.
Author: A. J. Lowe - Copyright: Silicon Chip

Source: 
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Paraphase Tone Controller

As opposed to the widespread Baxandall circuit (dating back to 1952!) a ‘paraphrase’ tone control supplies a straight frequency response as long as the bass and treble controls are in the same position. This unique property makes the ‘paraphase’ configuration of interest if only treble or bass needs to be adjusted - it is not possible to adjust both at the same time! Essentially, it’s the difference in setting of the tone controls that determines the slope of the frequency response, and the degree of bass/treble correction. The circuit is simplicity itself, based on two networks C1-C2-C3/R9-R10-R11 and C5-C6-C7/R12-R13-R14.

Paraphase Tone Controller Circuit Picture:


The first is for the high frequencies (treble) response, the second, for the low frequencies (bass). The roll-off points have been selected, in combination with C4 and C8, for the sum of the two output signals to re-appear with a ‘straight’ frequency response again at the output. Roughly equal output levels from the networks are ensured by R6 = 7.15 k and R8 = 6.80 k. However, the operating principle requires the input signals to the two networks to be in anti-phase. For best operation the networks are driven by two buffers providing some extra gain.

Paraphase Tone Controller Circuit diagram:
  

The gain of IC1.D is slightly higher than that of IC1.C to ensure the overall response curve remains as flat as possible at equal settings of the tone controls. Because each network introduces a loss of about 1.72 (times), IC1.D and IC1.C first amplify the signal. The gain is set at about 8 (times) allowing input signal levels up to 1 V to pass the circuit at maximum gain and distortion-free. The gain also compensates the attenuation if you prefer to keep the tone controls at the mid positions for a straight response.

Parts and PCB layout:


Parts and PCB Layout
To audio fans, the circuit is rewarding to experiment with, especially in respect of the crossover point of the two networks. R3 and R4 determine the control range, which may be increased (within limits) by using lower resistor values here. The values shown ensure a tone control range of about 20 dB. IC1.B buffers the summed signal across R15. C9 removes any DC-offset voltage and R16 protects the output buffer from the effects of too high capacitive loads. R17, finally, keeps the output at 0 V. The choice of the quad opamp is relatively uncritical. Here the unassuming TL074 is used but you may even apply rail to rail opamps as long as they are stable at unity gain. Also, watch the supply voltage range. A simple circuit board was designed for the project. Linear-law potentiometers may be fitted directly onto the board. Two boards are required for a stereo application. The relevant connections on the boards are then wired to a stereo control potentiometer.

Specification:
  • Current consumption (no signal) 8 mA
  • Max. input signal 1 Veff (at max. gain)
  • Gain at 20 Hz +13.1 dB max. –6.9 dB min.
  • at 20 kHz +12.2 dB max. –7.6 dB min
  • Gain (controls at mid position) 2.38 x
  • Distortion (1 Veff, 1 kHz) 0.002% (B = 22kHz) 0.005% (B = 80 kHz)
COMPONENTS LIST
Resistors
R1-R4 = 10k
R5,R7 = 1k
R6 = 7k15
R8 = 6k80
R9,R10,R11 = 8k2
R12,R13,R14 = 2k2
R15 = 1M
R16 = 100R
R17 = 100k
P1,P2 = 100k preset or chassis-
mount control potentiometer, linear law
Capacitors
C1,C2,C3 = 47nF MKT, lead pitch 5mm
C4 = 68nF MKT, lead pitch 5mm
C5,C6,C7 = 10nF MKT, lead pitch 5mm
C8,C10,C11 = 100nF MKT, lead pitch 5mm
C9 = 2µF2 MKT, lead pitch 5mm or 7.5mm
Semiconductors
IC1 = TL074
Miscellaneous
K1,K2 = line socket, PCB mount, e.g.
T-709G (Monacor/Monarch)

Source:   http://www.ecircuitslab.com/2011/06/paraphase-tone-controller.html
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Friday, December 20, 2013

Warning Light and Marker Light Circuit Diagram

This is a Warning Light and Marker Light Circuit Diagram. A flashing light of high brightness and short duty cycle is often desired to provide maximum visibility and battery life. This necessitates using an output transistor, which can supply the cold filament surge current of the lamp while maintaining a low saturation voltage. The oscillation period and flash duration are determined in the feedback loop, while the use of a photo transistor sensor minimizes sensitivity variations. 




Warning Light and Marker Light Circuit Diagram

Warning Light and Marker Light Circuit Diagram
 
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MP3 FM Transmitter

Heres a simple VHF FM transmitter that could be used to play audio files from an MP3 player or computer on a standard VHF FM radio. The circuit use no coils that have to be wound. This FM transmitter can be used to listen to your own music throughout your home. When this FM transmitter used in the car, there is no need for a separate input to the car stereo to play back the music files from your MP3 player.

USB FM Transmitter Project Image

MP3-FM-Transmitter Projecat

To keep the circuit simple as well as compact, it was decided to use a chip made by Maxim Integrated Products, the MAX2606 [1]. This IC from the MAX2605-MAX2609 series has been specifically designed for low-noise RF applications with a fixed frequency. The VCO (Voltage Controlled Oscillator) in this IC uses a Colpitts oscillator circuit. The variable-capacitance (varicap) diode and feedback capacitors for the tuning have also been integrated on this chip, so that you only need an external inductor to fix the central oscillator frequency.

t is possible to fine-tune the frequency by varying the voltage to the varicap. Not much is demanded of the inductor, a type with a relatively low Q factor (35 to 40) is sufficient according to Maxim. The supply voltage to the IC should be between 2.7 and 5.5 V, the current consumption is between 2 and 4 mA. With values like these it seemed a good idea to supply the circuit with power from a USB port.

USB FM Transmitter Schematics Circuit Diagram
MP3-FM-Transmitter-Schematic -Circuit Diagram

 Parts List

Resistors 
(all SMD 0805)
R1,R2 = 22kΩ
R3 = 4kΩ7
R4,R5 = 1kΩ
R6 = 270Ω
P1 = 10kΩ preset, SMD (TS53YJ103MR10 Vishay Sfernice, Farnell # 1557933)
P2 = 100kΩ preset, SMD(TS53YJ104MR10 Vishay Sfernice, Farnell # 1557934)
Capacitors (all SMD 0805)
C1,C2,C5 = 4μF7 10V
C3,C8 = 100nF
C4,C7 = 2nF2
C6 = 470nF
Inductors
L1 = 390nF, SMD 1206 (LQH31HNR39K03L Murata, Farnell # 1515418)
L2 = 2200Ω @ 100MHz, SMD, common-mode choke, 1206 type(DLW31SN222SQ2L Murata, Farnell #1515599)
Semiconductors
IC1 = MAX2606EUT+, SMD SOT23-6 (Maxim Integrated Products)
Miscellaneous
K1 = 3.5mm stereo audio jack SMD (SJ1-3513-SMT
CUI Inc, DIGI-Key # CP1-3513SJCT-ND)
K2 = 5-pin header (only required in combination with 090305-I pre-emphasis circuit)
K3 = USB connector type A, SMD (2410 07 Lumberg, Farnell # 1308875)

A common-mode choke is connected in series with the USB connections in order to avoid interference between the circuit and the PC supply. There is not much else to the circuit. The stereo signal connected to K1 is combined via R1 and R2 and is then passed via volume control P1 to the Tune input of IC1, where it causes the carrier wave to be frequency modulated. Filter R6/C7 is used to restrict the bandwidth of the audio signal. The setting of the frequency (across the whole VHF FM broadcast band) is done with P2, which is connected to the 5 V supply voltage.

The PCB designed uses resistors and capacitors with 0805 SMD packaging. The size of the board is only 41.2 x 17.9 mm, which is practically dongle-sized. For the aerial an almost straight copper track has been placed at the edge of the board. In practice we achieved a range of about 6 metres (18 feet) with this. There is also room for a 5-way SIL header on the board. Here we find the inputs to the 3.5 mm jack plug, the input to P1 and the supply voltage. The latter permits the circuit to be powered independently from the mains supply, via for example three AA batteries or a Lithium button cell. Inductor L1 in the prototype is a type made by Murata that has a fairly high Q factor: minimum 60 at 100 MHz.

USB FM Transmitter PCB Layout 

MP3-FM-Transmitter-PCB-Layout

Take care when you solder filter choke L2, since the connections on both sides are very close together. The supply voltage is connected to this, so make sure that you don’t short out the USB supply! Use a resistance meter to check that there is no short between the two supply connectors before connecting the circuit to a USB port on a computer or to the batteries.

P1 has the opposite effect to what you would expect (clockwise reduces the volume), because this made the board layout much easier. The deviation and audio bandwidth varies with the setting of P1. The maximum sensitivity of the audio input is fairly large. With P1 set to its maximum level, a stereo input of 10 mVrms is sufficient for the sound on the radio to remain clear. This also depends on the setting of the VCO. With a higher tuning voltage the input signal may be almost twice as large (see VCO tuning curve in the data sheet). Above that level some audible distortion becomes apparent. If the attenuation can’t be easily set by P1, you can increase the values of R1 and R2 without any problems.

Measurements with an RF analyzer showed that the third harmonic had a strong presence in the transmitted spectrum (about 10 dB below the fundamental frequency). This should really have been much lower. With a low-impedance source connected to both inputs the bandwidth varies from 13.1 kHz (P1 at maximum) to 57 kHz (with the wiper of P1 set to 1/10). In this circuit the pre-emphasis of the input is missing. Radios in Europe have a built-in de-emphasis network of 50 μs (75 μs in the US). The sound from the radio will therefore sound noticeably muffled. To correct this, and also to stop a stereo receiver from mistakenly reacting to a 19 kHz component in the audio signal, an enhancement circuit Is published elsewhere in this issue (Pre-emphasis for FM Transmitter, also with a PCB). Author: Mathieu Coustans, Elektor Magazine, 2009

Notice:
The use of a VHF FM transmitter, even a low power device like the one described here, is subject to radio regulations and may not be legal in all countries.




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Thursday, December 19, 2013

4 Amps Photovoltaic Solar Charge Controller

The use of solar photovoltaic (PV) energy sources is increasing due to global warming concerns on the one hand, and cost effectiveness on the other. Many engineers involved in power electronics find solar power tempting and then addictive due to the ‘green’ energy concept. The circuit discussed here handles up to 4 amps of current from a solar panel, which equates to about 75 watts of power. A charging algorithm called ‘pulse time modulation’ is introduced in this design. The current flow from the solar panel to the battery is controlled by an N-channel MOSFET, T1. This MOSFET does not require any heat sink to get rid of its heat, as its RD-S(on) rating is just 0.024 Ω.

Schottky diode D1 prevents the battery discharging into the solar panel at night, and also provides reverse polarity protection to the battery. In the schematic, the lines with a sort-of-red highlight indicate potentially higher current paths. The charge controller never draws current from the battery—it is fully powered by the solar panel. At night, the charge controller effectively goes to sleep. In daytime use, as soon as the solar panel produces enough current and voltage, it starts charging the battery. The battery terminal potential is divided by resistor R1 and trimpot P1.

4 Amps Photovoltaic (Solar) Charge Controller Circuit DIagram
4 Amps Photovoltaic (Solar) Charge Controller Circuit Diagram
The resulting voltage sets the charge state for the controller. The heart of the charge controller is IC1, a type TL431ACZ voltage reference device with an open-collector error amplifier. Here the battery sense voltage is constantly compared to the TL431’s internal reference voltage. As long as the level set on P1 is below the internal reference voltage, IC1 causes the MOSFET to conduct. As the battery begins to take up the charge, its terminal volt- age will increase. When the battery reaches the charge-state set point, the output of IC1 drops low to less than 2 volts and effectively turns off the MOSFET, stopping all current flow into the battery.


With T1 off, LED D2 also goes dark. There is no hysteresis path provided in the regulator IC. Consequently, as soon as the current to the battery stops, the output of IC1 remains low, preventing the MOSFET to conduct further even if the battery voltage drops. Lead-acid bat- tery chemistry demands float charging, so a very simple oscillator is implemented here to take care of this. Our oscillator exploits the negative resistance in transistors—first discovered by Leo Esaki and part of his studies into electron tunneling in solids, awarded with the Nobel Prize for Physics in 1973. In this implementation, a commonplace NPN transistor type 2SC1815 is used.

When the LED goes out, R4 charges a 22-μF capacitor (C1) until the voltage is high enough to cause the emitter-base junction of T2 to avalanche. At that point, the transistor turns on quickly and discharges the capacitor through R5. The voltage drop across R5 is sufficient to actuate T3, which in turn alters the reference voltage setting. Now the MOSFET again tries to charge the battery. As soon as the battery voltage reaches the charged level once more, the process repeats. A 2SC1815 transistor proved to work reliably in this circuit. Other transistors may be more temperamental—we suggest studying Esaki’s laureate work to find out why, but be cautioned that there are Heavy Mathematics Ahead.

As the battery becomes fully charged, the oscillator’s ‘on’ time shortens while the ‘off’ time remains long as determined by the timing components, R4 and C1. In effect, a pulse of current gets sent to the battery that will shorten over time. This charging algorithm may be dubbed Pulse Time Modulation. To adjust the circuit you’ll need a good digital voltmeter and a variable power supply. Adjust the supply to 14.9 V, that’s the 14.3 volts bat- tery setting plus approximately 0.6 volts across the Schottky diode.

Turn the trimpot until at a certain point the LED goes dark, this is the switch point, and the LED will start to flicker. You may have to try this adjustment more than once, as the closer you get the comparator to switch at exactly 14.3 V, the more accurate the charger will be. Disconnect the power supply from the charge controller and you are ready for the solar panel. The 14.3 V setting mentioned here should apply to most sealed and flooded-cell lead-acid batter- ies, but please check and verify the value with the manufacturer. Select the solar panel in such a way that its amps capability is within the safe charging limit of the battery you intend to use.

Author: T. A. Babu (India - Elektor)

Resistors:
R1 = 15kΩ
R2,R3 = 3.3kΩ 1% R4 = 2.2MΩ
R5 = 1kΩ
P1 = 5kΩ preset

Capacitors:
C1 = 22μF 25V, radial

Semiconductors:
D1 = MBR1645G (ON Semiconductor) D2 = LED, 5mm
IC1 = TL431ACLP (Texas instruments)
T1 = IRFZ44NPBF (International Rectifier)
T2 = 2SC1815 (Toshiba) (device is marked: C1815)
T3 = BC547

Miscellaneous:
K1,K2 = 2-way PCB terminal block, lead pitch 5mm
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Low Cost Universal Battery Charger

Low cost solution for charging of both NiCd and NiMh batteries
Here is the circuit diagram of a low cost universal charger for NiCD - NiMH batteries. This circuit is Ideal for car use. It has ability to transform a mains adapter in to a charger . This one can be used to charge cellular phone, toys, portables, video batteries, MP3 players, ... and has selectable charge current. An LED is located in circuit to indicate charging. Can be built on a general purpose PCB or a veroboard. I hope you really like it.
Picture of the circuit:a_low_cost_universal_charger circuit schematic_for_nicd_nimh_batteries 
 A Low Cost Universal Charger Circuit Schematic
Circuit diagram:
a_low_cost_universal_charger_circuit_diagram_for_nicd nimh batteries
A Low Cost Universal Charger Circuit Diagram
Parts:
R1 = 120R-0...5W
R2 = See Diagram
C1 = 220uF-35V
D1 = 1N4007
D2 = 3mm. LED
Q1 = BD135
J1 = DC Input Socket
Specifications:
  • Ideal for in car use.
  • LED charge indication.
  • Selectable charge current.
  • Charges Ni Cd or NiMH batteries.
  • Transforms a mains adapter into a charger.
  • Charge cellular phone, toys, portables, video batteries …
Features:
  • LED function indication.
  • Power supply polarity protected.
  • Supply current: same as charge current.
  • Supply voltage: from 6.5VDC to 21VDC (depending on used battery)
  • Charge current (±20%): 50mA, 100mA, 200mA, 300mA, 400mA. (selectable)
Determining the supply voltage:
This table indicates the minimum and maximum voltages to supply the charger. See supply voltage selection chart below.
Example:
To charge a 6V battery a minimum supply voltage of 12V is needed, the maximum voltage is then 15V.
Voltage selection:
supply_voltages_selection_chart_for_ ow cost universal_battery Charger
Voltage Selection Chart For Low Cost Universal Battery Charger
Determining the charge current:
Before building the circuit, you must determinate how much current will be used to charge the battery or battery pack. It is advisable to charge the battery with a current that is 10 times smaller then the battery capacity, and to charge it for about 15 hours. If you double the charge current , then you can charge the battery in half the time. Charge current selection chart is located in diagram.

Example:
A battery pack of 6V / 1000mAh can be charged with 100mA during 15 hours. If you want to charge faster, then a charge current of 200mA can be used for about 7 hours.
Caution:
The higher charge current, the more critical the charge time must be checked. When faster charging is used, it is advisable to discharge the battery completely before charging. Using a charge current of 1/10 of the capacity will expand the lifetime of the battery. The charge time can easily be doubled without damaging the battery.
Note:
  • Mount the transistor together with the heatsink on the PCB, bend the leads as necessary. Take care that the metal back of the transistor touches the heatsink. Check that the leads of the transistor do not touch the heatsink.
Source : http://www.ecircuitslab.com/2011/08/low-cost-universal-battery-charger.html
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Wednesday, December 18, 2013

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.

12V Powered 12V Lead Acid Battery Charger with Indicator

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. 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.

12V Powered 12V Lead Acid Battery Charger with Indicator

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. 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 Powered 12V Lead Acid Battery Charger with Indicator

Note that if the charge output is short-circuited, the over-current 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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It is the time when the shipment of phone booster

It is the time when the shipment of phone booster has been arranged.
Belonging to the target customers potential consumers in order to turn them into effective customer must understand why the customer needs your product, your product can help customers solve any problem, which needs to be done a lot of market research and customer interviews work, to really understand consumers, to achieve "customer-centric". Compared with similar products, your product to potential customers in what has created a unique value, unique advantages, there must be rational, objective analysis, in order to find the target consumer "non-bought compelling reasons"; If your products are differentiated features, you can communicate the value of your product information with potential customers. The manufacturer can get rid the inappropriate part of the imported technology of phone booster .
They agree with the value of your product, enlarge your advantage, weakening your shortcomings, to "sell ideas" of the realm, in order to sell a higher price; If your product does not have any differences in features, belonging to the popular and dependable, and competitors the product compared to what unique value, can only rely on the lowest price to attract consumers. Each customer inquiry when we have to try to understand clearly the customer via chat and meet with the judge, his right to speak, is the boss or just a messenger? Price: to the price, but also pay attention to skills for their own interests, not to indulge in (if you feel that one up to ask the price, that is asked many home, the price is certainly care about. It is to ensure the good quality, strict parameter, perfect technology and high performance of phone booster .
The best time directly to the reserve price, you can retain customers, this is a very important step to pull). The interests of customers first, that you do and the people that do (you do not know to say goodbye to home in the end to what price, but you at least want to investigate how the market is almost the price is kind of, so as not to report the outrageous.) services: services must be better, do not look to be a single, feeling a bit indifferent, emotions without reservation by phone to convey the past must be enthusiastic, to help customers solve problems, understand the customers questions about the point where the right remedy (to make people feel, your service really let him enjoy, even if you price a little bit higher than the others will leave because of your service). The customer will definitely have high and higher requirements towards quality and performance of phone booster .
Switch on the power supply of phone booster
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Tuesday, December 17, 2013

Wideband Wien Oscillator with Single Gang Pot

This Wien bridge oscillator (after Max Wien, 1866–1938) produces a low-distortion sine wave of constant amplitude, from about 15 Hz to 150 kHz. It requires just four opamps and will work off a single 9-volt battery. Also, unlike most Wien bridge oscillators, it does not require a dual-gang potentiometer for tuning. Op amp IC2b provides an artificial ground so that the circuit will operate from a unipolar supply (9 V battery or power pack). IC2a is the main amplifier for the oscillator. The frequency range is divided into four decades by 2-pole, 4-way rotary switch SW1.

Only one arm of the Wien network is varied, but the change in positive feedback that would normally result is compensated for by IC1b, which works to bootstrap R2, thereby changing the negative feedback enough to maintain oscillation. A linear change in the resistance of the tuning pot results in a roughly logarithmic change in frequency. To get a more conventional linear change a log-taper pot is used wired so that rotating the knob anticlockwise causes frequency to increase.


You could use an anti-log pot the other way around if you prefer, but these things are notoriously hard to find. IC1A is an integrator that monitors the amplitude of the output signal and drives an LED (D2). This must be mounted facing the LDR (light dependent resistor) and shielded from ambient light (for example, with a piece of heat-shrink tubing). IC1a is then able to control the gain of IC2a so that oscillation is maintained with minimum distortion.

The maximum output amplitude of the generator is about 2 Vp-p when the LED and LDR are mounted as close as possible. Distortion is less than 0.5 % in the lowest range, and too low for the author to measure in the higher ranges. Any LDR should work, provided its dark resistance is greater than 100 kO. If you do not have an LDR with such high resistance, try increasing R5 until oscillation starts. Breadboarded prototypes of the circuit were built by the author using dual and quad opamp packages, and both work equally well.

Author: Merlin Blencowe (Elektor)

Resistors:
R1,R2,R3,R6,R10,R11 = 10kO
R7 = 100kO
R4,R9,R12 = 100O
R5 = 12kO
R8 = 1kO
P1,P2 = 10kO potentiometer, logarithmic law
R13 = LDR, R(dark) >100kO, e.g. Excelitas Tech type
VT90N1 (Newark/Farnell # 2568243)

Capacitors:
C1,C5 = 1µF solid
C2,C6 = 100nF
C3,C7 = 10nF
C4,C8 = 1nF
C9-C12 = 47µF 16V, electrolytic, radial

Semiconductors:
D1,D2,D3 = 1N4148
D4 = LED, red, 5mm
IC1,IC2 = TL072ACP

Miscellaneous:
SW1 = 2-pole 4-position rotary switch, C&K Compo-
nents type RTAP42S04WFLSS
K1,K2 = PCB terminal block, 5mm pitch
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Some cell phone jammer have the built in cooling mechanism

Some cell phone jammer do not own the cooling function or cooling mechanism.
Domestic brand mobile phone companies do not have the core technology, the development of the control of others. The key components needed for the production of the domestic mobile phone baseband chip, RF chip and the underlying software are largely controlled by foreign companies. CDMA mobile phones due to lack of core technology, currently only take a "market for technology" Sino-foreign cooperative way, the development is fully controlled by others. Insufficient international marketing and export capacity is not strong. Domestic brand mobile phone, although in recent years has developed rapidly, but the products are mainly sold in the country, the vast majority did not go to foreign markets. These issues have become important issues constraining the development of the industry urgently to be addressed. Strategic Analysis of Japanese and Korean mobile phone manufacturer. Some cell phone jammer have the built-in cooling mechanism.
Domestic mobile phone manufacturers in the fashion of the prominent mobile phone design personalized features, price triggered a round of Diving Emergency perspective of Japanese and Korean mobile phone market strategy, we can say, not without reference to the domestic mobile phone manufacturers. Beijing in the enterprise market research study shows that personalized products lead the fashion to become the holy grail of Japanese and Korean manufacturers, especially MMS, color screen and camera phones. Made mobile phones to launch a rapid offensive in the price for the Pioneer, and triggered a collective "diving" of the mobile phone market, some foreign brands face the surging wave of price cuts had to fight with shine, Samsung, LG, Panasonic, NEC, Kyocera many days, the Korean brand in the Chinese market, has recently been the bright spot, have to be very impressive. Some cell phone jammer has the cooling fan.
Japanese and Korean mobile phone the way to win. European and American firms long-term leading the consumption trend of Chinas mobile phone market, so they bring in every shape design innovations have attracted many consumers to follow and favor. In fact, Japan and South Korea series of brand mobile phones in innovative design and personalized applications on the Ling-hui, to some extent higher than the European and American firms, just because they did not occupy the mainstream market, coupled with some manufacturers are not synchronized in China to promote the newly developed products , so can not give full play to their advantage. Faced with the enormous pressure of the American and European brands and domestic brands powerful offensive. Some cell phone jammer have some special cooling design.Japanese and Korean brand mobile phone manufacturers are not willing to supplement, the only market to continue to increase efforts to research and development of new products and push the new speed, began to clash with European and American brands. At the same time, Samsung also introduced a built-in rotating camera phone products to the China market.
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Monday, December 16, 2013

Simple Battery charger Circuit Diagram

This is a simple Battery charger circuit diagram. A diac is used in the gate circuit to provide work for the signal being applied to the gate. R1 a threshold level for firing the triac. C3 and R4 is selected to limit the maximum charging cur-provide a transient suppression network Rl, rent at full Totation of R2. R2, R3, Cl, and C2 provide a phase-shift net.


Simple Battery charger Circuit Diagram




Simple Battery charger Circuit Diagram
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