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Friday, November 7, 2014

Test Beeper For Your Stereo

The test beeper generates a sinusoidal signal with a frequency of 1,000 Hz, a common test frequency for audio amplifiers. It consists of a classical Wien- Bridge oscillator (also known as a Wien-Robinson oscillator). The network that determines the frequency consists here of a series connection of a resistor and capacitor (R1/C1) and a parallel connection (R2/C2), where the values of the resistors and capacitors are equal to each other. This network behaves, at the oscillator frequency (1 kHz in this case), as two pure resistors. The opamp (IC1) ensures that the attenuation of the net- work (3 times) is compensated for. In principle a gain of 3 times should have been sufficient to sustain the oscillation, but that is in theory. Because of tolerances in the values, the amplification needs to be (automatically) adjusted.

Test Beeper For Your Stereo circuit Diagram

Instead of an intelligent amplitude controller we chose for a somewhat simpler solution. With P1, R3 and R4 you can adjust the gain to the point that oscillation takes place. The range of P1 (±10%) is large enough the cover the tolerance range. To sustain the oscillation, a gain of slightly more than 3 times is required, which would, however, cause the amplifier to clip (the ‘round-trip’ signal becomes increasingly larger, after all). To prevent this from happening, a resistor in se-ries with two anti-parallel diodes (D1 and D2) are connected in parallel with the feedback (P1 and R3). If the voltage increases to the point that the threshold voltage of the diodes is exceed-ed, then these will slowly start to conduct.

The consequence of this is that the total resistance of the feedback is reduced and with that also the amplitude of the signal. So D1 and D2 provide a stabilising function. The distortion of this simple oscillator, after adjustment of P1 and an output voltage of 100 mV (P2 to maximum) is around 0,1%. You can adjust the amplitude of the output signal with P2 as required for the application. The circuit is powered from a 9-V battery. Because of the low current consumption of only 2 mA the circuit will provide many hours of service.

Wednesday, September 17, 2014

Portable CD Player Adapter For Car

Whenever Im in the car listening to my favourite CD, it always happens; my batteries go dead. To solve that problem, I built this extremely simple regulator circuit. It steps down the 12V from the lighter socket to 9V which is used by the CD player. Different CD players (I have a Sony Discman) may require different voltages, so just use the correct regulator. All the 78xx series regulators have the same pin out, so the circuit is universal.

Portable CD Player Adapter For Car Circuit daigram

Parts List

Part       Total Qty.                     Description

C1            1                        1000uF 25V Electrolytic Capacitor
C2                      1              10uF 25V Electrolytic Capacitor
C3            1                        1uF 15V Elextrolytic Capacitor
C4                      1                        0.1uF 15V Electrolytic Capacitor
U1        1                        7809 Or Other Regulator (See "Notes")    See Notes
MISC      1                        Cigarette Lighter Plug, Plug For CD Player (See "Notes"),      Heat Sink For U1, Wire, Case.

Notes

The voltage your CD player needs will determine which regulator you use. For 9V, use the 7809. For 6V, use the 7806. For the unlikely 5V use the 7805. Remember that whatever regulator you use, you will need to heat sink it. The metal case or metal cover on the case makes a great heat sink.
I built the circuit in a small case with the long wire to the cigarette lighter plug coming out one end, then another, slightly shorter wire going out the other end to the CD player.

Triple check your wiring. You would hate to ruin an expensive CD player because you reversed one of the connections or hooked the regulator up backwards.

Tuesday, September 9, 2014

Rear Fog Lamp For Vintage Cars Wiring diagram Schematic

According to current legislation in many countries, vintage cars must also be fitted with a fog lamp at the rear. In modern cars, there is a bit of schemary associated with the fog lamp switch to prevent the fog lamp from going on when the lights are switched on if the driver forgot to switch it off after the last patch of fog cleared up. The schema described here extends that technology back in time. The schema is built around a dual JK flip-flop (type 4027). T3 acts as an emitter follower, and it only supplies power to the schema when the lights are switched on.

For safety reasons, the supply voltage is tapped off from the number plate lamp (L2), because it is on even if you accidentally drive with only the parking lights on. The wire that leads to the number plate lamp usually originates at the fuse box. As the states of the outputs of IC1a and IC1b are arbitrary when power is switched on, the reset inputs are briefly set high by the combination of C1, R1 and T1 when the lights are switched on (ignition switch on). That causes both Q outputs (pins 1 and 15) to go low. IC1a and IC1b are wired in toggle mode (J and K high).

The Set inputs are tied to ground (inactive). The driver uses pushbutton switch S1 to generate a clock pulse that causes the outputs of the flip-flops to toggle. The debouncing schema formed by C2, R4 and T2 is essential for obtaining a clean clock pulse, and thus for reliable operation of the schema. C1 and C2 should preferably be tantalum capacitors. The Q output of IC1b directly drives LED D1 (a low-current type, and yellow according to the regulations). The Q output of IC1a energises relay Re1 via T4 and thus applies power to the rear fog lamp L1.

Rear Fog Lamp For Vintage Cars Circuit Diagram

Free-wheeling diode D2 protects T4 against inductive voltage spikes that occur when the relay is de-energised. In older-model cars, the charging voltage of the generator or alternator is governed by a mechanical voltage regulator. These regulators are less reliable than the electronic versions used in modern cars. For that reason, a Zener diode voltage-limiter schema (D3 and R9) is included to keep the voltage at the emitter of T3 below 15 V and thus prevent the 4027 from being destroyed by an excessively high voltage.

The supply voltage for the schema is tapped off from the fuse box. An accessory terminal is usually present there. Check to make sure it is fed from the ignition switch. The pushbutton switch must be a momentary-contact type (not a latching type). Ensure that the pushbutton and LED have a good ground connection. Fit the LED close to the button.

The following ‘Bosch codes’ are used in the schematic:

15 = +12 V from ignition switch
58K = number plate lamp
86 = relay coil power (+) IN
85 = relay coil power OUT
30 = relay contact (+) IN
87 = relay contact OUT

Author: Eric Vanderseypen - Copyright: Elektor Electronics Magazine

Sunday, September 7, 2014

USB Charger For Lithium Ion battery

USB Battery Charger For Lithium Ion battery with the LM3622 is a series of lithium ion battery charger. This charger circuit operates using power from the USB source PC.

Current consumption of a series of USB Battery Charger For Lithium Ion battery with 400mA LM3622 is limited by R1, so it does not exceed the current maximum limit that can be given by a USB computer. Brains from USB Battery Charger For Lithium Ion battery with IC LM3622 , it is a national of having special technical specification charger for lithium ion batteries.

In a series of USB Battery Charger For Lithium Ion with LM3622 R1 0.25 Ohm value that serves to limit the charging current 400mA to the battery. Q2 and Q1 is the last part of the USB Battery Charger For Lithium Ion battery with the LM3622. In principle, USB Battery Charger For Lithium Ion with LM3622 identify the condition of the battery full charged battery voltage via pin 6 LM3622. USB Series Lithium Ion Battery Charger For LM3622 is equipped with a switch to select the battery that was in charge of 2.7 volts or 2.1 volts.

Friday, September 5, 2014

Adaptor for Bass Guitar Amp

Adaptor for Bass Guitar Amp. These days, music is a major hobby for the young and not-so-young. Lots of people enjoy making music, and more and more dream of showing off their talents on stage. But one of the major problems often encountered is the cost of musical equipment. How many amateur music groups sing through an amp borrowed from a guitarist or bass player?

This is where the technical problems arise not in terms of the .25” (6.3 mm) jack, but in terms of the sound quality (the words are barely understandable) and volume (the amp seems to produce fewer decibels than for a guitar). What’s more, unpredictable feedback may cause damage to the speakers and is very unpleasant on the ear. This cheap little easy-to-build project can help solve these technical problems.
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Circuit diagram :

Vocal Adaptor for Bass Guitar Amp Circuit Diagram

A guitar (or bass guitar) amplifier is designed first and foremost to reproduce the sound of the guitar or bass as faithfully as possible. The frequency response of the amp doesn’t need to be as wide or as flat as in hi-fi (particularly at the high end), and so this sort of amplifier won’t permit faithful reproduction of the voice.

If you build an adaptor to compensate for the amp’s limited frequency response by amplifying in advance the frequencies that are then attenuated by the amp, it’s possible to improve the quality of the vocal sound. That’s just what this schema attempts to do.

The adaptor is built around the TL072CN low-noise dual FET op-amp, which offers good value for money. The NE5532 can be used with almost the same sound quality, but at (slightly) higher cost. The schema breaks down into two stages. The first stage is used to match the input impedance and amplify the microphone signal.

For a small 15 W guitar or bass amplifier, the achievable gain is about 100 (gain = P1/R1). For more powerful amplifiers, the gain can be reduced to around 50 by adjusting P1. The second stage amplifies the band of frequencies (adjustable using P2 and P3) that are attenuated by the guitar amp, so as to be able to reproduce the (lead) singer ’s voice as clearly, distinctly, and accurately as possible. To refine the adaptor and tailor it to your amplifier and speaker, don’t be afraid to experiment with the component values and the type of capacitors.

The schema can readily be powered using a 9 V battery, thanks to the voltage divider R4/R5 which converts it into a symmetrical ±4.5 V supply.

Wednesday, September 3, 2014

Build a Receiver Af Noise Limiter For Low Level Signals Wiring diagram Schematic

Build a Receiver Af Noise Limiter For Low-Level Signals Circuit Diagram. A preamplifier in the audio frequency range amplifies a noisy audio signal to drive a diode clipper.Suitable audio input levels would be in the 10-mV to 1-V range.

Receiver Af Noise Limiter For Low-Level Signals Circuit Diagram

Tuesday, September 2, 2014

Contrast Control for LCDs

The adjustment control for the contrast of an LC-Display is typically a 10-k potentiometer. This works fine, provided that the power supply voltage is constant. If this is not the case (for example, with a battery power supply) then the potentiometer has to be repeatedly adjusted. Very awkward, in other words. The schema described here offers a solution for this problem.

The aforementioned potentiometer is intended to maintain a constant current from the contrast connection (usually pin 3 or Vo) to ground. A popular green display with 2x16 characters ‘supplies’ about 200 µA. At a power supply voltage of 5 V there is also an additional current of 500 µA in the potentiometer itself. Not very energy efficient either. Now there is an IC, the LM334, which, with the aid of one resistor, can be made into a constant current source. The schema presented here ensures that there is a current of 200 µA to ground, independent of the power supply voltage. By substituting a 2.2-k? potentiometer for R1, the current can be adjusted as desired.

Circuit diagram:The value of R1 can be calculated as follows: R1 = 227x10-6 x T / I. Where T is the temperature in Kelvin and I is the current in ampères. In our case this results in:
R1 = 227x10-6 x 293 /
(200x10-6)
R1 = 333R

Note that the current supplied by the LM334 depends on the temperature. This is also true for the current from the display, but it is not strictly necessary to have a linear relationship between these two. Temperature variations of up to 10° will not be a problem however. This schema results in a power saving of over 25% with an LCD that itself draws a current of 1.2 mA. In a battery powered application this is definitely worth the effort! In addition, the contrast does not need to be adjusted as the battery voltage reduces. When used with LCDs with new technologies such as OLED and PLED it is advisable to carefully test the schema first to determine if it can be used to adjust the brightness.

Contrast Controller Circuit Diagram For LCDs:

Contrast Controller Circuit Diagram For LCDs

The value of R1 can be calculated as follows: R1 = 227x10-6 x T / I. Where T is the temperature in Kelvin and I is the current in ampères. In our case this results in:

R1 = 227x10-6 x 293 /
(200x10-6)
R1 = 333R

Note:

The current supplied by the LM334 depends on the temperature. This is also true for the current from the display, but it is not strictly necessary to have a linear relationship between these two. Temperature variations of up to 10° will not be a problem however. This schema results in a power saving of over 25% with an LCD that itself draws a current of 1.2 mA. In a battery powered application this is definitely worth the effort! In addition, the contrast does not need to be adjusted as the battery voltage reduces. When used with LCDs with new technologies such as OLED and PLED it is advisable to carefully test the schema first to determine if it can be used to adjust the brightness.

Dome light dimmer for Cars

This unique schema makes your dome light look cool. Usually when the car door is closed, the dome light just goes OFF. With this schema, you can have our dome light fade slowly in brightness and finally go OFF. This slow dimming of the light gives a very good feeling at night. It looks very romantic!

http://www.electronic-diagram-diagrams.com/carsimages/3.gif

The schema can be explained as follows: When the car door is open, the push to off switch of the door is ON and hence it charges the 22uF capacitor fully. The opamp is acting as a voltage follower and its output is same as the voltage across the capacitor, which is 12V when the capacitor is fully charged. Due to a high voltage at the output of the IC, the transistor saturates, turning ON the bulb to full brightness.

Now when the door is closed, the door switch is pushed in and hence the switch goes OFF. When the switch is OFF, the capacitor starts discharging slowly through VR1 and the 10K resistor and the voltage across it decreases slowly. Hence at the output of IC 741 also the voltage decreases gradually, hence decreasing the base current to the transistor. This produces a slowly decreasing current through the bulb and the bulb fades out and finally when the capacitor is fully discharged, the bulb goes OFF.

After building the schema, with the push-to-off switch in ON position (not pushed in) i.e. the car door open, adjust the preset VR2 to the required initial brightness of the bulb. Then push the switch in to turn it OFF(or close the door) and adjust VR1 for the time to bring the bulb from full brightness to OFF.
I would suggest you set VR1 and VR2 to their maximum values.

Sunday, August 31, 2014

4 x 6W POWER AMPLIFIER FOR CAR RADIO

This is a TDA7372 POWER AMPLIFIER FOR CAR RADIO circuit diagram

Circuit Diagram

4 x 6W POWER AMPLIFIER FOR CAR RADIO

Wednesday, August 27, 2014

Separation filter crossover for car subwoofer

The figure shows a circuit diagram of car crossover (cr

ossover) for the subwoofer. The input stage of the transistor Q1 is a differential summing amplifier, and the switch S1 is used to switch polarity. Switched-capacitor filter with a slope of 24 dB per octave (chip IC1) is the basis of continuously tunable filter. Potentiometer R13 controls the filter cutoff frequency on the chip IC1, adjusting its clock speed. Because the switched-capacitor filters, by definition, work with discrete signals at the input of IC1 should be restrictive filter (antialiasing). Such a low pass filter of the second order constructed by transistors Q2 and Q3 and associated elements. The output signal of IC1 via pin 5 served on a subsonic filter with the possibility of lifting the lowest frequencies. When switch S2 is closed, then on the rise of the frequency characteristic occurs. Additional filtering is provided by infrasound capacitors C1 and C2 directly to the input of the crossover. The resistor R18 and the capacitor C 10 is assembled so-called remodeling filter, eliminating the remnants of the quantization noise. The power supply circuit, gathered on the integral regulator 78L08 (chip IC2), and provides the main supply voltage of 8.6 V, and the bias voltage of 4.8 V. The diode D1 protects the circuit from negative voltage spikes and incorrect wiring. Diode D2 displaces the output reference voltage stabilizer 78L08 0.6 V for receiving an output voltage of 8.6 V, and not B. 8

Original article source cxem.net

Tuesday, August 26, 2014

Simple Relay Fuse For Battery Charges Wiring diagram Schematic

This is a Simple Relay Fuse For Battery Charges Circuit Diagram. Charged capacitor C3 and momentary pushbutton switch S2 are used to momentarily energize relay RE 2. The batteiy under charge energizes the relay to hold it closed. S2 will energize the relay even if the battery is too far discharged initially to energize it.

Relay Fuse For Battery Charges Circuit Diagram

Sunday, August 24, 2014

Start up Aid for PCs Wiring diagram Schematic

Since one of the servers owned by the author would not start up by itself after a power failure this little schema was designed to perform that task.

The older PC that concerned did have a standby state, but no matching BIOS set-ting that allows it to start up unattended. Although a +5 V standby supply voltage is available, you always have to push a but-ton for a short time to start the computer up again. Modern PCs often do have the option in the BIOS which makes an automatic start after a power outage possible. After building in the accompanying schema, the PC starts after about a second. Incidentally, the push-button still functions as before.

The schema is built around two golden oldies: a NE555 as single-shot pulse generator and a TL7705 reset generator. The reset generator will generate a pulse of about 1 second after the supply voltage appears. The RC schema between the TL7705 and the NE555 provides a small trigger pulse during the falling edge of the 1 second pulse. The NE555 reacts to this by generating a nice pulse of 1.1RC. During that time the output transistor bridges the above mentioned pushbutton switch of the PC, so it will start obediently.

Other applications that require a short duration contact after the power supply returns are of course also possible.

Author : Egbert Jan van den Bussche – Copyright : Elektor

Mosfet Mixer Oscillator For Am Receivers Wiring diagram Schematic

This is a simple Mosfet Mixer Oscillator For Am Receivers Circuit Diagram. This schema is an improved front end for upgrading a transistor AM receiver. This front end is useful when the radio is to be used as a tune-able IF amplifier with shortwave converters.

Mosfet Mixer Oscillator For Am Receivers Circuit Diagram