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Showing posts with label simple. Show all posts

Wednesday, December 25, 2013

Simple Radio Wave Alarm

This simple circuit is sure to have the police beating a path to your door- however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat.

Simple Radio Wave Alarm Circuit Diagram :

Notes :

The circuit transmits on Medium Wave (this is the small problem with the police). IC1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates at just over 1MHz. This is modulated by an audio frequency (a continuous beep) produced by IC1b. When a hand or a foot approaches the sensor, the frequency of the transmitter (IC1a) drops appreciably.
Suppose now that the circuit transmits at 1MHz. Suppose also that your radio is tuned to a frequency just below this. The 1MHz transmission will therefore not be heard by the radio. But bring a hand or a foot near to the sensor, and the transmitters frequency will drop, and a beep will be heard from the radio.
Attach the antenna to a multiplug adapter that is plugged into the mains, and you will find that the Medium Wave transmission radiates from every wire in your house. Now place a suitably tuned Medium Wave radio near some wires or a plug point in your house, and an early-warning system is set up.
Instead of using the sheet of tin foil as the sensor, you could use a doorknob, or burglar bars. Or you could use a pushbutton and series resistor (wired in series with the 33K resistor - the pushbutton would short it out) to decrease the frequency of IC1a, so activating the system by means of a pushbutton switch. In this case, the radio would be tuned to a frequency just below that of the transmitter.

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Wednesday, September 4, 2013

Simple Metal Detector Using 555 Timer

This metal detector electronic project schematic circuit is designed using a simple 555 timer integrated circuit . As you can see in the schematic circuit , this metal detector electronic project requires few external electronic parts . This circuit detects metal and also magnets.

Metal Detector with 555 Timer Circuit Daigram

When a magnet is brought close to the 10mH choke, the output frequency changes. This metal detector project can be powered from a power supply that can provide an output DC voltage between 6 an 12 volt . If a metal is closer to the L1 coil , will produce a change of output oscillation frequency, that will generate a sound in the 8 ohms speaker

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Thursday, August 8, 2013

Simple Rumble Filter Circuit Diagram

This simple rumble filter circuit diagram is a two-section active HP filter using an LM387, with a cutoff below 50 Hz at 12-dB per octave. It will help reduce rumble as a result of turntable defects in record systems.

Simple Rumble Filter Circuit Diagram

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Tuesday, July 30, 2013

Simple Voltmeter Circuit

his circuit provides a simple means to determine the voltage of a low-impedance voltage source. It works as follows. P1, which is a 1-W potentiometer, forms a voltage divider in combination with R1. The voltage at their junction is buffered by T1, and then passed to reference diode D1 via R3. D1 limits the voltage following the resistor to 2.5 V. An indicator stage consisting of T2, R4 and LED D2 is connected in parallel with D1. As long as the voltage is not limited by D1, the LED will not be fully illuminated. This is the basic operating principle of this measurement circuit.

http://www.ecircuitslab.com/2011/06/simple-voltmeter-circuit.html

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Saturday, July 13, 2013

Simple Battery Low Voltage Beeper Circuit

Simple Battery Low Voltage Beeper circuit provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a periodic beeping sound to warn of the impending loss of power. The circuit was designed for monitoring solar systems, but it could also be useful for automotive and other 12V applications.

Specifications:

Nominal operating voltage: 12V
Idle current: 6ma
Low Voltage Warning current: 15ma

Theory:
U2 provides a 5V regulated voltage reference. U1 is wired as a comparator, it compares the fixed 5V regulated voltage to the voltage on the wiper of VR1, that is proportional to the 12V supply. When the supply drops below the set point, the output of U1 goes low, turning on Q1 and powering the beeper and the LED.

The beeper consists of U4, a tone generator, and U3, a low duty cycle pulse generator. The tone can be changed by adjusting R7, the beep rate can be changed by adjusting R5. A small amount of hysteresis is provided by R1 and the current through LED1 and the beeper, this separates the on and off points for the circuit.

Battery Low Voltage Beeper Circuit

Simple Battery Low Voltage Beeper circuit board was made by printing the pattern (see below) onto Press-n-peel blue circuit board transfer film with a laser printer. Etch the board, drill the holes, and assemble the parts on the board as per the board photo. Be sure to correctly orient the diode, electrolytic capacitors, ICs, and transistor. The CA3160 op-amp may be difficult to find, other low power CMOS op-amps may be substituted. A standard 741 op-amp would also work, but the idle current will be higher.

Alignment:
Connect the circuit to an adjustable DC voltage source. Set the voltage source to 11V or wherever you would like the circuit to turn on. Turn on switch S1. Adjust VR1 until the point where LED1 just comes on and the beeping starts.

Use:
Connect the circuit to the 12V source that you wish to monitor. There should be a fuse somewhere between the battery and this circuit. Turn S1 on, if the battery voltage is above the set point, nothing should happen.
As the battery voltage drops below the set point, the LED will light and a periodic beeping will come from the speaker. If the beeping becomes annoying, turn off S1. Be sure to charge the battery soon, excessive discharging will shorten the life of most rechargeable batteries.

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Thursday, July 11, 2013

Simple Electronic Quiz Switch

One of the common rounds in the quizzes is the buzzer round. We are describing here a simple electronic circuit that can be used in any test or quiz competition. In this circuit, only four persons can participate, and every participant is assigned a certain number. Whenever a switch is pressed, the circuit locks the remaining three entries. At the same time, an alarm sounds and the designated switch number is displayed on the seven segment LED display.When a player presses his switch, the corresponding output of IC1 goes high. Let us suppose, when switch S1 is pressed, D1 input of IC1 goes low and its corresponding output Q1 goes high. As a result, current passes through D5 to piezo buzzer PZ1, which creates a beep. At the same time, current also passes through diodes D6-D7 to show the number on the LED display.

Circuit diagram:

Simple Electronic Quiz Switch Circuit Diagram

Similarly, when any other switch (S2-S4) is pressed, the corresponding number gets displayed on seven segment displaying DIS1 and buzzer sounds. Switch S5 is used to reset the display exclusively. Switch S5 is a push to on switch. The circuit is powered by 9V battery. Assemble the circuit on a general purpose PCB and enclose it in a suitable case along with seven segment display and piezo buzzer. The assembled circuit can be kept near the host and the switches connected through the external can be assigned to the players.

http://streampowers.blogspot.com/2012/06/simple-electronic-quiz-switch.html

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Wednesday, July 10, 2013

Simple 8 Channel DTMF Link Encoder

Generated millions of times every day by our telephone keypads, the eight DTMF frequencies were chosen so that the harmonics and intermodulation do not generate significant in-band signal levels. The signal is encoded as a pair of sine waves, ensuring that no frequency is a multiple of the other and the sum and difference between two frequencies does not match any single tone and that’s why DTMF sounds so ugly!T he DTMF encoder circuit show n here is based on the HT9200B tone generator device produced by Holtek and distributed by Futurlec among others. The encoder is complemented by a decoder elsew her e in this publication.

8-Channel DTMF Link: Encoder Schematic

The HT2900B is supplied as a nice old fashioned 14-pin device. It can be instructed by a microcontroller to generate 16 dual tones and (in serial mode only) 8 single tones from the DTMF pin output . It s 8 - pin ‘ younger brother’ the HT9200A provides a serial mode only whereas the HT9200B contains a select-able serial/parallel mode interface for various applications such as security systems, home automation, remote control through telephone lines, communication systems, etc.

A 74HC148 8-to-3 priority encoder is used to convert the ‘keypad’ information from S1–S8 into 3-bit tone selection words the HT9200B wants to see at its input. The ninth switch, S9, is connected to input D3 on the encoder chip. Pressing one of the switches S1–S8 generates a complementary 3-bit binary word at outputs A0, A1, A2 of IC1. IC2 then generates the dual tones accordingly to these binary codes.

Pressing S1–S8 generates the dual tones for DTMF digits C, B, A, #, *, 0, 9 and 8. By pressing and holding down S9 the DTMF digits 7, 6, 5, 4, 3, 2, 1 and D are generated.

To generate the eight single frequencies accurately a 3.58 MHz crystal quartz is connected to pin 2 and 3 of IC2. Pin 13 of the HT9200B supplies a DTMF signal of about 150 mV at a 5 KO load.

Pull-up resistor array R2 may be omitted if you substitute the 74HC148 with a 74LS148. R1 must be present in that case, otherwise it can be omitted.

The circuit consumes about 2 mA from a regulated 5 V supply. It should be easy to build on a small piece of prototyping board. link

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Tuesday, July 9, 2013

Simple Color Organ Circuit

Three Lamp-Channels Output Built-in Electret Microphone

A simple, satisfactory Color Organ can be built with a handful of cheap components. This design features: no mains supply transformer, built-in microphone and three widely adjustable frequency bands obtained by means of very simple, passive filters for Bass, Middle and Treble.
Circuit diagram :
Simple Color Organ-Circuit Diagram

Simple Color Organ Circuit Diagram

Due to the very low current consumption of this circuit, the mains supply can be conveniently reduced with no heat dissipation by the reactance of C1; then rectified by D1 and D2 and clamped to 24V by the Zener Diode D3. The music diffused by the loudspeaker(s) of any type of media player, is picked-up by the built-in microphone and the resulting signal is greatly amplified by a two-stage transistor audio amplifier Q1 and Q2.

At the output of the second stage, the audio signal is filtered and split into three fully adjustable frequency bands by means of a simple (though effective) passive filter formed by P1, P2, P3, R7, R8, C6 and C7, thus avoiding the complexity of op-amp based active filters. Transistors Q3, Q4 and Q5 are the drivers for the Triacs D4, D5 and D6 respectively, but can be omitted if high sensitivity Triac devices are used.

Parts:

P1,P2,P3_____10K Linear Potentiometers

R1_____470R   1/2W Resistor
R2_____100K   1/4W Resistor
R3_____1M   1/4W Resistor
R4_____22K   1/4W Resistor
R5_____220K   1/4W Resistor
R6_____15K   1/4W Resistor
R7_____1K5 1/4W Resistor
R8_____4K7 1/4W Resistor

C1_____330nF 400V Polyester Capacitor
C2_____470µF   35V Electrolytic Capacitor
C3,C4,C6_____100nF   63V Polyester or Ceramic Capacitors
C5_____1µF   63V Electrolytic Capacitor
C7_____4n7   63V Polyester or Ceramic Capacitor

D1,D2_____1N4007 1000V 1A Diodes
D3_____BZX79C24 24V 500mW Zener Diode
D4,D5,D6_____TIC206M 600V 4A TRIACs

Q1 to Q5_____BC547 45V 100mA NPN Transistors

MIC1_____Miniature Electret Microphone Capsule

SW1_____SPST Toggle Switch 250V 10-15A (See Notes)

PL1_____Male Mains Plug

SK1,SK2,SK3_____Female Mains Sockets

Notes :

sing the Triac types suggested in the Parts List, each channel can drive several incandescent lamp bulbs, up to about 800W, but in this case a separate heatsink must be used for each Triac.
Due to the absence of a mains transformer, avoid to connect this circuit to other appliances (e.g. to the output of an amplifier by means of a cable). Please use only the microphone enclosed into the main case to pick-up the music.
For 110-120V mains operation, C1 value must be doubled: use two 330nF capacitors wired in parallel or one 680nF 250V capacitor. No further modification is required.
SW1 must be a high voltage, high current switch, as it must withstand the total amount of current drawn by all bulbs wired to the three outputs of the circuit.

Warning! The device is connected to 230Vac mains, then some parts in the circuit board are subjected to lethal potential! Avoid touching the circuit when plugged and enclose it in a plastic or wooden box.

Streampowers

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Sunday, July 7, 2013

Simple Luggage Security Alarm Schematic

We usually lock our luggage utilizing a chain-and-lock arrangement when in travelling by a train of bus. But, still we are worried, apprehending that someone may possibly break the chain and steal our luggage. The following schematic is really a very simple and easy build luggage security alarm circuit to alert you when a person tries to break the chain.

Transistor T1 allows supply to the sound generator chip when the base current begins flowing through it. When the wire (thin enameled copper wire of 30 to 40 SWG, applied for winding transformers) loop around the chain is cracked by someone, the base of transistor T1, which was previously linked with positive rail, becomes opened. Because of this, transistor T1 gets forward biased to extend the positive power source towards the alarm circuit. Link
In idle mode, the power source consumption within the circuit is lowest and as a result, it could possibly be utilized for numerous travel hrs.
To make it possible for generation of various alarm sounds, joints to pin 1 and 6 could be designed as shown in the following table:

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Saturday, July 6, 2013

Simple 9V battery replacement circuit

This power supply circuit contains two charge-pump DC-DC converters which can delivery up to -10V for a 2,0V to 3,6V input voltage battery. For a current consumption of 7mA the output voltage it will drop to 9V, but this is enough to power a portable handheld instrument. The overall efficiency it will be up to 74% for a 2V input voltage and 60% for a 3.6V lithium polymer battery cell.

First charge-pump DC-DC converter based on MAX 619 from Maxim , C70851 smd code , delivers a regulated 5V +/- 4% output at max. 50mA. To maintain the greatest efficiency over the entire input voltage range, the MAX619s internal charge pump operates as a voltage doubler when input voltage ranges from 3.0V to 3.6V, and as a voltage tripler when it ranges from 2.0V to 2.5V.

The second charge pump converter use a TC682 circuit from Microchip and it provides an inverted doubled (-10V) output from a single positive supply (+5V regulated). An on-board 12kHz (typical) oscillator frequency provides the clock and only 3 external capacitors are required for full circuit implementation. Low output source impedance (typically 140Ω), provides output current up to 10mA.

10V DC-DC converter placement of circuit components

Components placement on printed circuit boardMore voltage convertors:

5V dc-dc converter this circuit can deliver over 1.6A at 5V and still work at 2.0V

Max761 boost converter module from 5V to 13.5V or 12V, ideal for Flash Memory Programming

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Wednesday, July 3, 2013

Simple LED flasher circuit using NE555 timer IC

This circuit consumes more power, but its advantage is when you need a variable flash rate, like for strobe circuits. You can actually use this circuit as a remote control for strobes that have a remote input. Of course, it has many other applications besides strobes.

R1, R2, C1 and the supply voltage determine the flash rate. Using a regulated power supply will do much to insure a stable flash rate. For a variable flash rate, replace R1 with a 1 megohm pot in series with a 22k resistor.
The duty cycle of the circuit (the percentage of the time LED 1 is on to the time it is off during each cycle) is deterimed by the ratio of R1 to R2. If the value of R1 is low in relationship to R2, the duty cycle will be near 50 percent. If you use both LEDs, you will probably want a 50 percent duty cycle. On the other hand, if R2 is low compared to R1, the duty cycle will be less than 50 percent. This is useful to conserve battery life, or to produce a strobe type effect, when only LED1 is used.
The NE555 timer chip can be damaged by reverse polarity voltage being applied to it. You can make the circuit goof proof by placing a diode in series with one of the supply leads.
The purpose of R3 and R4 is to limit current through the LEDs to the maximum they can handle (usually 20 milliamps). You should select the value of these according to the supply voltage. 470 ohms works well with a supply voltage of 9-12 volts. You will need to reduce the value for lower supply voltages.
Rainbow Kits offers several kits to build the above circuit. You can also order these kits from RadioShack.com. The Radio Shack catalog numbers (and web pages) are as follows: standard kit with two 5mm red LEDs, (990-0067), kit with two red, two green and two yellow 3mm LEDs, (990-0063), kit with jumbo green LEDs, (990-0048), kit with jumbo red LEDs, (990-0049). You can also buy all the parts to build the circuit at your local Radio Shack store, including a circuit board (276-159B).

I have built a miniature strobe circuit as follows. Use a 250k pot in series with a 4.7k resistor for R1. The 4.7k resistor sets the upper flash rate limit. Use 2.2k for R2. That sets a really short duty cycle. For this circuit, you dont use LED 2 or R4. For LED 1, I used a two Radio Shack white LEDs in series and no R-3. The circuit runs on a 9 v battery. link

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Sunday, May 5, 2013

Simple Siren Circuit

This circuit will generate siren sound when S1 pressed and increate sound frequency becuase capacitor C1 charged when switch S1 released the frequency will decreated(C1 discharged).

Try to change resistor R3 if you need to change time interval from low to high frequency and vise versa.

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Saturday, April 13, 2013

Simple Electrification Unit

The circuit is meant for finishing up hurtless scans with high-voltage pulses and performances in a identical method as an electrified fence generator. The p.r.f. (pulse repetition frequency) is decided by the time constant of community R1-C3 within the feedback loop of op amp IC1a: with values as special, it's about zero.5 Hz. The stage following the op amp, IC1b, converts the oblong signal into slim pulses. Differentiating network R2-C4, together with the switching threshold of the Schmitt set off inputs of IC1b, determines the pulse length, which right here is set 1.5 ms. The output of IC1b is linked in an instant to the gate of thyristor THR1, so that this software is brought about by the pulses.

The requisite excessive voltage is generated with the assist of a small primarys transformer, whose secondary winding is right here used as the important. This winding, at the side of C2, kinds a resonant circuit. Capacitor C3 is charged to the professionalvision voltage (12 V) by means of R3.When a pulse output via IC1b set offs the thyristor, the capacitor is discharged by the use of the secondary winding. The vitality saved within the capacitor is, on the reverse hand, not misplaced, however is saved within the magnetic field professionalduced by means of the transformer when present flows thru it. When the capacitor is discharged, the present stops, whereupon the magnetic container give ways. This induces a counter e.m.f. in the transformer winding which opposes the voltage previous utilized to the transformer.

Circuit diagram:

$\"Simple_Electrification_Unit_Circuit$

Simple Electrification Unit Circuit Diagram

This signifies that the direction of the present continues to be the identical. However, capacitor C2 is now charged in the reverse sense, in order that the prospective throughout it is terrible. When the magnetic field of the transformer has again the stored vitality to the capacitor, the course of the present reverses, and the poorly charged capacitor is discharged via D1 and the secondary winding of the transformer. As soon as the capacitor starts to be discharged, there is no present through the thyristor, which due to this fact switches off. When C2 is discharged further, diode D1 is reverse-biased, in order that the present loop to the transformer is damaged, whereupon the capacitor is charged to 12 V once more by the use of R3. At the next pulse from IC1b, this process repeats itself.

Since the transformer after every discharge of the capacitor at its main set offs no longer best a main, but in addition a secondary voltage, every triggering of the thyristor result ins two closely spaced voltage pulses of opposite polarity. These induced voltages at the secondary, that is, the 230 V, winding, of the transformer are, as a effect of the better flips ratio, much larger than those on the major side and may attain a few hundred volts. However, for the explanation that vitality saved in capacitor C2 is fairly small (the present drain is best about 2 mA), the output voltage cannot harm man or animal. It is adequate, then again, to lead to a clearly discernible muscle convulsion.

Author: P. Lay - Copyright: Elektor Electronics

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Thursday, April 11, 2013

Simple Mini Audio Amplifier circuit

Description

Here is a simple and humble 2 Watts mini audio amplifier circuit suitable for small pocket radios and other portable audio gadgets.The circuit is based on Phillips Semiconductors IC TDA 7052.The amplifier can be run even from a 3V Mercury button cell.This makes it ideal for battery operated gadgets.

The IC TDA7052 is a mono output amplifier coming in a 8-lead DI package (DIP). The device is mainly designed for battery-operated portable audio circuits. The features of TDA 7052 include ,no external components needed, no switch-on or switch-off click sounds , great overall stability ,very low power consumption(quiescent current 4mA) , low THD, no heat sinks required and short-circuit proof.

The gain of TDA 7052 is fixed internally at 40 dB. . To compensate the reduction of output power due to low voltage supply the TDA7052 uses the Bridge-Tied-Load principle (BTL) which can provide an output of around 1 to 2 W Rms(THD = 10%) into an 8 Ohm load with a power supply of 6 V.

In the circuit the potentiometer can be used to control the volume. Capacitor C1 and C2 are meant for filtering the supply voltage if a battery eliminator is used as supply source. For operations using a battery C1 and C2 are not necessary.

Mini Audio Amplifier Circuit Diagram with Parts List:

Notes.

Assemble the circuit on a good quality PCB or common board .
If you are a little expert, you can assemble the circuit in a match box including the speaker.

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Wednesday, April 10, 2013

Simple VGA to BNC Adapter Converter Circuit

There are monitors which only have three BNC inputs and which use composite synchronization (‘sync on green’). This circuit has been designed with these types of monitor in mind. As can be seen, the circuit has been kept very simple, but it still gives a reasonable performance. The principle of operation is very straightforward. The RGB signals from the VGA connector are fed to three BNC connectors via AC-coupling capacitors. These have been added to stop any direct current from entering the VGA card. A pull-up resistor on the green output provides a DC offset, while a transistor (a BS170 MOSFET) can switch this output to ground. It is possible to get synchronisation problems when the display is extremely bright, with a maximum green component.

In this case the value of R2 should be reduced a little, but this has the side effect that the brightness noticeably decreases and the load on the graphics card increases. To keep the colour balance the same, the resistors for the other two colors (R1 en R3) have to be changed to the same value as R2. An EXOR gate from IC1 (74HC86) combines the separate V-sync and H-sync signals into a composite sync signal. Since the sync in DOS-modes is often inverted compared to the modes commonly used by Windows, the output of IC1a is inverted by IC1b. JP1 can then by used to select the correct operating mode. This jumper can be replaced by a small two-way switch, if required.

This switch should be mounted directly onto the PCB, as any connecting wires will cause a lot of interference. The PCB has been kept as compact as possible, so the circuit can be mounted in a small metal (earthed!) enclosure. With a monitor connected the current consumption will be in the region of 30 mA. A 78L05 voltage regulator provides a stable 5 V, making it possible to use any type of mains adapter, as long as it supplies at least 9 V. Diode D2 provides protection against a reverse polarity.

LED D1 indicates when the supply is present. The circuit should be powered up before connecting it to an active VGA output, as otherwise the sync signals will feed the circuit via the internal protection diodes of IC1, which can be noticed by a dimly lit LED. This is something best avoided.

Resistors:
R1,R2,R3 = 470Ω
R4 = 100Ω
R5 = 3kΩ3
Capacitors:
C1,C3,C5 = 47µF 25V radial
C2,C4,C6,C7,C10 = 100nF ceramic
C8 = 4µF7 63V radial
C9 = 100µF 25V radial
Semiconductors:
D1 = LED, high-efficiency
D2 = 1N4002
T1 = BS170
IC1 = 74HC86
IC2 = 78L05
Miscellaneous:
JP1 = 3-way pinheader with jumper
K1 = 15-way VGA socket (female), PCB mount (angled pins)
K2,K3,K4 = BNC socket (female), PCB mount, 75Ω . Link

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Friday, April 5, 2013

Simple Electronic Lock

There are six (or more) push switches. To unlock you must press all the correct ones at the same time, but not press any of the cancel switches. Pressing just one cancel switch will prevent the circuit unlocking. When the circuit unlocks it actually just turns on an LED for about one second, but it is intended to be adapted to turn on a relay which could be used to switch on another circuit. Please Note: This circuit just turns on an LED for about one second when the correct switches are pressed. It does not actually lock or unlock anything!

Circuit diagram :

Simple Electronic Lock Circuit Diagram

Stripboard Layout :

Parts :

resistors: 470, 100k ×2, 1M
capacitors: 0.1μF, 1μF 16V radial
on/off switch
push-switch ×6 (or more)
stripboard 12 rows × 25 holes
red LED
555 timer IC
8-pin DIL socket for IC
battery clip for 9V PP3

A kit for this project is available from RSH Electronics: www.kpsec.freeuk.com

http://streampowers.blogspot.com/2012/06/simple-electronic-lock.html

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Monday, April 1, 2013

Simple 3 Channel Audio Splitter

Simple circuitry, Passive high-quality amplification and distribution

This circuit is suitable to amplify and distribute the audio signals. The input audio signal is applied to the J1 and after passing through the P1, It is buffered and amplified by the IC1 prepared to redistribute. It has 3 outputs to drive 3 audio lines with 300 ohms impedance.

3 Channel Audio Splitter Circuit diagram :

Parts:

J1 = RCA Socket (See Notes)
P1 = 100K-Potentiometre
R* = 10K-100K
R1 = 560K
R2 = 1K
R3 = 2.2K
R4 = 2.7K
R5 = 2.7K
R6 = 330R
R7 = 330R
R8 = 330R
C1 = 100uF-25V
C2 = 100uF-25V
C3 = 100uF-25V
D1 = BZX79C18
D2 = BZX79C18
Q1 = BC337
Q2 = BC327
IC1 = NE5532-34

Notes:

J1 will be RCA Audio input female socket.
R* is on your choice it can be choose between 10K to 100K resistor.
Output capacitor’s value is between 100uf to 470uf and power handling is 25V to 50V.
You can power up this circuit via +12V/-12V regulated supply but you have to remove following parts Q1-Q2-C2-C3-D1-D2.
Maximum power ratings +35V/-35V

Source : www.ecircuitslab.com/2011/05/three-channel-audio-splitter.html

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Wednesday, March 27, 2013

Simple DPA 220 schematic

T1 to T6 create the input differential stage. The D7 and D8 zener diodes stabilize at 5V. These are just the simplest low-power zeners, only they have to be coupled in tolerance of 200 milivolts, which should not be a problem. T1 to T6 are common all-purpose low-power transistors with high Hfe. These six and maybe the next four have to be coupled in tolerance of 25%.

The T7 and T8 are fast, switching application types.

T9 and T10 have to be fast and must hold a high voltage, thus the best are the "video" types - BF469/470. T15 and T16 are the same types.

The C9, C10 and C15 should stand voltages higher than usual 50 V - I dont know why.

D3 to D6 can be any silicon type, not Scottky, the ones listed below are just all-purpose low-current ones for 150 V. These diodes should be rather fast - "switching types".

The T11 and T12 stabilize the BIAS current for the power stage. T11 also serves as a temperature sensor, and is mounted to the cooler of power transistors.

T13 and T14 secure the output current - in cooperation with R38 and R39.

The output transistors used here are Tesla types - Tesla is a former local devices manufacturer - the pair in each branch can be replaced with a single power darlington, like BD649/BD650. They should have Pc > 150W, Ic > 15A, Uceo > 100V.

In this case obviously the R38+R40 / R39+R41 must be connected parallel. These resistors should be able to absorb high power - at least 2 W, but Id use 5W ones.

The output filter improves stability of the amp when working with complex impedance of speakers - it is quite important. The resistors are high-power ones again, the coil is 13 turns of a 1.2 mm wire on a 8 mm thorn (diameter). R43 is placed coaxially in the coil.

The schematic also includes power supply capacitors and rectifier - the capacitors size is not crucial, generally the bigger the better. The rectifier originally consists of four silicon 10A diodes, but you can use whatever you have - rectifier bridge etc. The trafo should be a 2 * 30 V / 7 A type so that you have +/- 40 V on the power supply capacitors.

In the scheme theres also a thermistor that is supposed to be connected to some additional circuits that secure temperature and other things. The complementary input stage of DPA amps is an unmistakable heir of earlier designs published by Mr. Borbely in several issues of Volume 1984 of the Audio Amateur. Link

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Tuesday, March 26, 2013

Simple Combination Lock Circuit

This simple combination lock accommodates codes from 1-9 digits long, with the only restriction being that the same digit cannot be used twice. The circuit shows strapping for a 4-digit code, in this case "2057". Any unused switches are strapped to ground. When power is applied, the 330nF capacitor connected to pin 1 of inverter IC1a is discharged, holding it at a logic low level. The high output is inverted by a second gate (IC1b), with the result being a logic low on pin 4. This pulls Q1’s emitter low via D1, causing the transistor to conduct. The falling voltage on the collector then pulls the input of IC1c low, which in turn resets counter IC2.

On reset, output O0 (pin 3) of IC2 goes high, charging the 330nF capacitor via D2 and the 33kΩ resistor. If switch S2 is now pressed, Q2s emitter will be pulled high and so Q2 conducts, applying a rising positive voltage to one end of the 1MΩ resistor. This resistor and the 33nF capacitor act as a switch "debounce" circuit, delaying the pulse through IC1e by about 33ms. After the delay, the output of IC1e goes low. However, counter IC2 does not increment at this stage, since it needs a positive-going edge at the clock input (pin 14). When the switch is released, Q2 turns off, IC1e’s output goes high after the debounce period and the counter advances to the next state (ie. O0 goes low and O1 goes high).

Circuit diagram:

simple-combination-lock-circuit-diagram1

Simple Combination Lock Circuit Diagram

When output O0 (pin 3) goes low, the 330nF capacitor starts discharging through the 33kΩ and 10MΩ resistors. This allows about 3s for the operator to press the next button. If no button is pressed within this period, IC1b’s output goes low, which pulls Q1’s emitter low and resets the counter via IC1c. Hence the code entry must be restarted. When the second digit of the code is entered (0 in this example), Q2’s emitter is again pulled high. Q2 thus turns on and after the debounce delay, IC1e’s output goes low. When the switch is released, Q2 turns off, IC1e’s output goes high and the counter advances to state 2.

Note that while the switch is pressed, IC1d’s output is high, recharging the 330nF capacitor and therefore resetting the 3s delay. Thus, the operator is allowed another 3s to press the next digit. This process is repeated for each digit in the sequence. If the wrong switch is pressed at any point, IC2 is reset as described above. Conversely, if the correct code is entered, IC1 advances to state 4 (for our 4-digit example) on release of the fourth switch. Output O4 then goes high and turns on Q3 and relay 1. Q3 can handle up to about 300mA of load current. If more current is required, then either a Darlington or power Mosfet can be substituted. D4 is required if the load is inductive (eg, a relay, solenoid, etc).

Author: Len Cox - Copyright: Silicon Chip Electronics

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Monday, March 25, 2013

Simple Gated Alarm

Sometimes the need arises for a simple, gated, pulsed alarm. The circuit shown here employs just four components and a piezo sounder and is unlikely to be out-done for simplicity. While it does not offer the most powerful output, it is likely to be adequate for many applications.

Circuit diagram :

Simple Gated Alarm Circuit Diagram

A dual CMOS timer IC type 7556 is used for the purpose, with each of its two halves being wired as a simple astable oscillator (a standard 556 IC will not work in this circuit, nor will two standard 555’s). Note that the CMOS7556 is supplied by many different manufacturers, each using their own type code prefix and suffix. The relevant Texas Instruments product, for instance, will be marked ‘TLC556CN’. The circuit configuration used here is seldom seen, due probably to the inability of this oscillator to be more than lightly loaded without disturbing the timing. However, it is particularly useful for high impedance logic inputs, since it provides a simple means of obtaining a square wave with 1:1 mark-space ratio, which the ‘orthodox’ configuration does not so easily provide.

IC1.A is a slow oscillator which is enabled when reset pin 4 is taken High, and inhibited when it is taken Low. Out-put pin 5 of IC1.A pulses audio oscillator IC1.B, which is similarly enabled when reset pin 10 is taken High, and inhibited when it is taken Low.

In order to simplify oscillator IC1.B, piezo sounder X1 doubles as both timing capacitor and sounder. This is possible because a passive piezo sounder typically has a capacitance of a few tens of nanofarads, although this may vary greatly. As the capacitor-sounder charges and discharges, so a tone is emitted. The value of resistor R2 needs to be selected so as to find the resonant frequency of the piezo sounder, and with this its maximum volume. The circuit will operate off any sup-ply voltage between 2 V and 18 V. A satisfactory output will be obtained at relatively high supply voltages, but do not exceed 18 V.

Author :Rev. Thomas Scarborough –Copyright : Elektor

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