shared wiring: April 2013

Tuesday, April 30, 2013

Adjustable Duty Cycle

http://www.delabs-circuits.com/cirdir/digital/555/del00012.png

The circuit shown here can be used to convert a digital input signal having any desired duty cycle into a output signal having a duty cycle that can be adjusted between 10% and 80% in steps of 10%. The circuit is built around a 74HC4017 decade Johnson counter IC. Individual pulses appear on the ten outputs (Q0–Q9) of this IC at well-defined times, depending on the number of input pulses (see the timing diagram). This characteristic is utilised in the circuit. The selected output is connected via a jumper to the Reset input (MR, pin 2) of a 74HC390 counter. A High level resets the output signals of the 74HC390 counter. Q9 of the 74HC4017 is permanently connected to the CP0 input of the counter to set the Q0 output of the 74HC390 (pin 3) High on its negative edge.

As can be seen from the timing diagram, which shows the signals for a duty cycle of 30% as an example, this produces a signal with exactly the desired duty cycle. The circuit cannot be used to produce a duty cycle of 10% (which would be equivalent to taking the signal directly from the Q0 output of the 74HC4017) or 90%. In both cases, the edges of the pulses used for the count input (CP0) and the asynchronous reset input (MR) of the 74HC390 would coincide, with the result that the output state of the 74HC390 would not be unambiguously defined. The input frequency must be ten times the desired output frequency.
If the second half of the 74HC390 is wired as a prescaler, a prescaling factor of 2, 5 or 10 can be achieved, thus allowing the ratio of the of input frequency to the output frequency to be 20, 50 or 100. If the circuit is built using components from the 74HC family, it can be operated with supply voltages in the range of 3–5 V.

Saturday, April 13, 2013

Model Railway Short Circuit Beeper

Short circuits in the tracks, points or wiring are almost inevitable when building or operating a model railway. Although transformers for model systems must be protected against short circuits by built-in bimetallic switches, the response time of such switches is so long that is not possible to immediately localise a short that occurs while the trains are running, for example. Furthermore, bimetallic protection switches do not always work properly when the voltage applied to the track circuit is relatively low.

Circuit diagram :

Model Railway Short-Circuit Beeper Circuit Diagram

The rapid-acting acoustic short-circuit detector described here eliminates these problems. However, it requires its own power source, which is implemented here in the form of a GoldCap storage capacitor with a capacity of 0.1 to 1 F. A commonly available reed switch (filled with an inert gas) is used for the current sensor, but in this case it is actuated by a solenoid instead of a permanent magnet. An adequate coil is provided by several turns of 0.8–1 mm enamelled copper wire wound around a drill bit or yarn spool and then slipped over the glass tube of the reed switch. This technique generates only a negligible voltage drop. The actuation sensitivity of the switch (expressed in ampèreturns or A-t)) deter-mines the number of turns required for the coil. For instance, if you select a type rated at 20–40 A-t and assume a maxi-mum allowable operating current of 6 A, seven turns (40 ÷ 6 = 6.67) will be sufficient. As a rule, the optimum number of windings must be determined empirically, due to a lack of specification data.

As you can see from the circuit diagram, the short-circuit detector is equally suitable for AC and DC railways. With Märklin transformers (HO and I), the track and lighting circuits can be sensed together, since both circuits are powered from a single secondary winding.

Coil L1 is located in the common ground lead (‘O’ terminal), so the piezoelectric buzzer will sound if a short circuit is present in either of the two circuits. The (positive) trigger voltage is taken from the lighting circuit (L) via D1 and series resistor R1. Even though the current flowing through winding L1 is an AC or pulsating DC current, which causes the contact reeds to vibrate in synchronisation with the mains frequency, the buzzer will be activated because a brief positive pulse is all that is required to trigger thyristor Th1. The thyristor takes its anode voltage from the GoldCap storage capacitor (C2), which is charged via C2 and R2. The alarm can be manually switched off using switch S1, since although the thyris-tor will return to the blocking state after C2 has been discharged if a short circuit is present the lighting circuit, this will not happen if there is a short circuit in the track circuit. C1 eliminates any noise pulses that may be generated.

As a continuous tone does not attract as much attention as an intermittent beep, an intermittent piezoelectric generator is preferable. As almost no current flows during the intervals between beeps and the hold current through the thyristor must be kept above 3 mA, a resistor with a value of 1.5–1.8 kΩ is connected in parallel with the buzzer. This may also be necessary with certain types of continuous-tone buzzers if the operating current is less than 3 mA. The Zener diode must limit the operating voltage to 5.1 V, since the rated volt-age of the GoldCap capacitor is 5.5 V.

source by : Streampowers

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

A Car Battery Monitor

A close name on the street can in reality center of consideration your thoughts on the importance of having a battery display in a car. I had been playing a nice week of touring around the united states of americaside at a leisurely tempo and taking in the beautiful surroundings on a daily basis. It wasnt until the ultimate day, with the big rush to return house, that I had to power at evening.My house is deep within the us of a and on the highway I used to be travelling the closest petrol station may be 80km away. I was traveling thru a neighborhood that is stuffed with open-cut coal mines and massive closely loaded semi-trailers continuously pound the highways, travelling at somewhat excessive velocitys. It used to be around 8pm at evening and the complete thing used to be very dark no side highway milds or home milds anyplace.

Just as I was once going up a hill, the solarshines started out to dim and the engine coughed. A massive semi-trailer loomed within the rear-vision mirror as I pushed the seize in and tried to relaxationart. My pace was falling rapidly and my lights were blacked out - I was once like a sitting duck in the direction of the highway, as the semi-trailer came swiftly bearing down on me. I simply managed to tug the auto off the street, as the semi-trailer got here screaming prior, missing me via inches! After calling for the lend a hand of the NRMA, the issue was once discovered to be a fault in the alternator, which used to be failing to charge the battery. The battery voltage had been falling underneath the heavy load of the milds and on the worst imaginable time, there was now not enough power for the lights or the motor.

After the preliminary shock wore off, I put on my thinking cap to come up with a PIC-based method to the problem. What was once in level of fact wanted used to be a show and a buzzer, to get my consideration must the voltage fall out of doors a targeted vary. So my design standards was set, a sequence of LEDs might indicate the voltage and a buzzer would also be used to warn of problems.

Main Features:

Visual indication of battery voltage
Audible warning when voltage becomes low
Screw terminals for easy connection
Simple and straightforward to construct

Circuit details:

The circuit is in line with PIC16F819 18-pin microcontroller which has an analog-to-digital (A/D) input to observe the battery voltage and outputs able to driving LEDs right away, to maintain the part count down. There are seven LEDs in all, giving a just right range of voltage indication. The topmost LED, LED1, comes on for voltages above 14V as a manner to happen when the battery is absolutely charged. LED2 point outs for voltages between 13.5V and 14V while LED3 point outs between thirteenV and 13.5V. Normally, probably the mostse LEDs shall be on. LED4 quilts 12.5V to 13V while LED5 quilts 12V to 12.5V. LED6 duvets from eleven.5V to 12V while LED7 comes on for voltages below 11.5V. These two LEDs are backed up with the help of the piezo chime which beeps for voltages between 11.5V and 12V and change intos more insistent for voltages under eleven.5V.

That might seem fairly conservative. After all, most automobiles will start and no longer using a bothers, even if the battery voltage could be a slightly under 12V, wont they? Well, no. Some brand new automotives will happily crank the motor at voltages beneath 11V however their engine management won't let the motor begin except the voltage is above 11V. So dont assume that a modern automobile will all the time begin reliably. This little battery monitor may easily prevent an extraordinarily inconvenient failure to start! So lets describe the the rest of the circuit. The incoming supply is linked by method of diode D1 which provides safety once extrast reverse polarity whereas zener diode ZD1 gives safety from spike voltages.

A usual 7805 3-terminal regulator is then used to provide a steady 5V to the microcontroller. The battery voltage is sensed by means of a voltage divider the use of 33kΩ and 100kΩ resistors. This delivers the voltage down to inside the 0-5V vary for the A/D input of the PIC16F819. Port B (RB0 to RB7) of the microcontroller is then used to force the quite loads of LEDs, with current limiting equipped by the use of the 330Ω resistor network. RB7, pin thirteen, drives a swaping transistor for the piezo buzzer.

Software:

For the software, the design follows the basic template for a PIC microcontroller. Port A and its ADC (analog-to-digital converter) operate are set up while port B functions because the output for the LEDs and buzzer. Once the set-up is full, a reading will likely be taken at port RA2, the enter for the A/D convertor. This reading is then when compared with a sequence of prices to resolve the range of the voltage. This is just like a collection of \"if\" statements in Basic language. If the voltage is found to be inside a certain vary, the related port B pin will almost definitely be fliped on. If the voltage is below 12V, the buzzer will most definitely be turned on for a brief duration, to signal a low battery situation. As the voltage falls beneath 11.5V, the frequency of the beeps will elevate, to signal elevated urgency.

Building it:

All the parts are installed on a small PC board measuring 46 x 46mm (available from Futurlec). The place to begin should be the IC socket for the PIC16F819, as this is best to mount whereas the board is naked. The next item will even be the PC terminal block. The resistors and capacitors can then follow. Make certain the electrolytics are inserted with perfect polarity.

Make sure that you don't confuse the zener (ZD1) with the diode when you in finding yourself putting in them; the diode is the larger bundle of the two.

Even extra essential, dont get the 78L05 3-terminal regulator and the 2N3906 transistor mixed up; they arrive in similar packages. The 78L05 will most certainly be labelled as such while the 2N3906 will most probably be labelled \"3906\". And you ought to definitely insert them the precise manner round. The buzzer should even be installed with the right polarity. The 330Ω current limiting resistors are all in a 10-pin in-line package. There are four green LEDs, two yellow and one crimson. They wish to be installed in line and with the precise orientation.

Testing:

Before you insert the PIC16F819 microcontroller, do a voltage examine. Connect a 12V supply and test for the presence of 5V between pins 14 & 5 OF IC1. If 5V just isn't existing, verify the polarity of regulator REG1 and the polarity of the diode D1. If these take a appear ats are OK, insert the IC and check the unit over a variety of voltage between 9V and 15V. Make positive that every one LEDs come on in sequence and the piezo buzzer beeps for voltages under 12V.

Now it is subject of putting in the unit to your automobile. It is best to install the unit in a visual position for the driving force. However, it must now not obscure every other devices. The unit will have to be linked to the autos 12V supply after the ignition switch. This will flip the unit off with the other instruments and prevent battery drain whereas the motor is simply not working.

Author :Alan Bonnard Copyright : Silicon Chip Publications Pty Ltd

Friday, April 12, 2013

Flugzeugepiper Pa28 Airshampoo Aerodrome

Piper Aircraft on Flugzeuge De Piper P28 T Cockpit

Flugzeuge De Piper P28 T Cockpit.

Piper Aircraft on Piper Aircraft Feierte Vom 9 Bis Zum 11 November 2012 An Ihrem

Piper Aircraft on Piper Aircraft Feierte Vom 9 Bis Zum 11 November 2012 An Ihrem

Piper Aircraft Feierte Vom 9 Bis Zum 11 November 2012 An Ihrem.

Piper Aircraft on Cr Piper Aircraft Piper Seneca V

Piper Aircraft on Cr Piper Aircraft Piper Seneca V

Cr Piper Aircraft Piper Seneca V.

Piper Aircraft on The Original Piper Aircraft Company Declared Bankruptcy In 1991 In

Piper Aircraft on The Original Piper Aircraft Company Declared Bankruptcy In 1991 In

The Original Piper Aircraft Company Declared Bankruptcy In 1991 In.

Piper Aircraft on Flugzeuge De Piper Saratoga Tc Ln Aaf

Piper Aircraft on Flugzeuge De Piper Saratoga Tc Ln Aaf

Flugzeuge De Piper Saratoga Tc Ln Aaf.

Piper Aircraft on Piper Cub Logo All Vector Logo

Piper Cub Logo All Vector Logo.

Piper Aircraft on Flugzeuge De Piper P28 T Cockpit Map

Piper Aircraft on Flugzeuge De Piper P28 T Cockpit Map

Flugzeuge De Piper P28 T Cockpit Map.

Piper Aircraft on Flugzeuge De Piper Saratoga Tc Ln Aaf

Piper Aircraft on Flugzeuge De Piper Saratoga Tc Ln Aaf

Flugzeuge De Piper Saratoga Tc Ln Aaf.

Piper Aircraft on Flugzeuge De Piper Pa28 Im Airshampoo Aerodrome

Piper Aircraft on Flugzeuge De Piper Pa28 Im Airshampoo Aerodrome

Flugzeuge De Piper Pa28 Im Airshampoo Aerodrome.

Piper Aircraft on Flugzeuge De Piper Saratoga Tc Ln Aaf

Piper Aircraft on Flugzeuge De Piper Saratoga Tc Ln Aaf

Flugzeuge De Piper Saratoga Tc Ln Aaf.

Maximite Stepper Motor Interface

This simple circuit and program listing allows the Maximite microcomputer (SILICON CHIP, March-May 2011) to control a stepper motor. It could be expanded to allow for the control of multiple motors, with four of the Maximite’s external I/O pins used to control each motor with identical driver circuits. A ULN2003 Darlington transistor array (IC1) switches current through the stepper motor’s two windings in either direction. When one of the four Maximite output pins (8, 12, 16 & 20, corresponding to I/Os 19, 17, 15 & 13) goes high, the corresponding output pin on IC1 goes low, sinking current through a motor winding. Conversely, when these pins are high, the corresponding Darlington transistor is off and so no current flows through that portion of the winding.

Maximite stepper motor interface

Maximite stepper motor interface

The centre tap of each motor winding is connected to a current source comprising PNP Darlington transistor Q1 and some resistors. The maximum current is determined by the resistive divider driving its high-impedance base, setting the base voltage to around 9.1V when it is fully on. By adding Q1’s base-emitter voltage (1.4V at 0.5A, as per the data sheet) we can determine that there will be around 1.5V across the 3.3O resistor (12V - 10.5V), resulting in a current of 1.5V ÷ 3.3O = ~450mA. Transistor Q1 must be fitted with a medium-sized flag heatsink (Jaycar HH8504, Altronics H0637) or larger to handle its maximum dissipation of (10.5V - 4.9V) x 450mA = 2.5W.

When one of the Darlington transistors switches off and current flow through the corresponding motor winding ceases, the inductive winding generates a back-EMF current which causes the voltage across that winding to spike. IC1 has internal “free-wheeling” diodes from each output to the COM pin, which is connected to the +12V supply. The back-EMF current flows back into the power supply and the voltage spikes are clamped at about 12.7V, so that the Darlington transistors do not suffer collector reverse breakdown, which might damage them.

A 470µF capacitor provides supply bypassing for the motor while a 47kO pull-up resistor and toggle switch/pushbutton S1 drives input pin 9 of the Maximite, allowing manual control of the motor direction. Table 1 shows the sequence in which the output pins are driven to turn the motor forward; the steps are run backwards for reverse operation. The delay between the steps determines the speed at which the motor rotates. The source code of the sample program is available for download from the SILICON CHIP website (maximite_stepper_motor.bas).

Source by : Streampowers

Constructing a Universal Power Supply using LM317 Rise

This is a basic, Universal Power Supply voltage regulator circuit the usage of an LM317, 3-terminal regulator in a TO-220package. The Universal Power Supply output voltage can be set to anywhere within the range one.5V to 30V by way of picking resistances. By using a potentiometer, R2, as of the resistors that you could dial up the output voltage wished. Either AC or DC enter can be provided to the PCB by using a socket or terminal block. Connection will additionally be either way round. This is because they've presentd a bridge rectifier on board. The input DC voltage to the regulator have to be at least two.5V above the necessary output voltage. An off/on change is equipped.

For a lot of applications (say 12V at 60mA) a heat sink wont be required. The LM317 will provide relatively larger output voltages than 30 volts. However, for most hobbyists over 30V wont be needed. So to make a small PCB they've used some electrolytic capacitors rated to 35 volts. To be safe for continuous operation the utmost enter DC voltage to the regulator must now not be over 33V. With a two.5V to three.0V drop throughout the regulator this may just increasingly provide a regulated output of 30V. You can draw up to one.5A from the LM317. In case you want greater then use an LM338T rated to 5A.

When out of doors capacitors are used with any IC regulator it is lovely apply so as to add safety diodes to prevent the capacitors discharging again in to the regulator in the event of extraordinary running stipulations, like a surprising short circuit on the input or the output, or a again emf from an inductive load. That is the function of D one and D Two.

The worth of R1 can vary anyplace from 120R to 1200R However, circuits from most different supplys choose using either 220R or 250R. They have used 240R or 250R. The voltage drop across R1is one.25V for all worths, and this is the key to the design. one.25V is the reference voltage of the regulator. Whatever current wafts through R1 also floats via R2, and the sum of the voltage drops across R1 and R2 is the output voltage. (Additional current Id also drifts in R2 however it's regularly 50uA so is negligible.)

The design components are:

VOUT = 1.25 (1 + R2/R1) volts, or alternatively

R2/R1 = (VOUT/1.25) - 1

So in case you beneathstand VOUT & R1 is 250R then that you could calculate R2. In case you find that the 5K potentiometer used forR2 does no longer give you the degree of positive keep watch over over the voltage output vary that you just want then you will have to use these formula to advantageous-tune R1 & R2 to raised applicable values.

Universal Power Supply Schematic Diagram

Mini Ups System

This circuit provides an uninterrupted power supply (UPS) to operate 12V, 9V and 5V DC-powered instruments at up to 1A current. The backup battery takes up the load without spikes or delay when the mains power gets interrupted. It can also be used as a workbench power supply that provides 12V, 9V and 5V operating voltages. The circuit immediately disconnects the load when the battery voltage reduces to 10.5V to prevent deep discharge of the battery. LED1 indication is provided to show the full charge voltage level of the battery. miniature white LEDs (LED2 and LED3) are used as emergency lamps during power failure at night.

Mini Ups System Circuit diagram:

Mini Ups System Circuit Diagram

A standard step-down transformer provides 12V of AC, which is rectified by diodes D1 and D2. Capacitor C1 provides ripple-free DC to charge the battery and to the remaining circuit. When the mains power is on, diode D3 gets forward biased to charge the battery. Resistor R1 limits the charging current. Potentiometer VR1 (10k) with transistor T1 acts as the voltage comparator to indicate the voltage level. VR1 is so adjusted that LED1 is in the ‘off’ mode. When the battery is fully charged, LED1 glows indicating a full voltage level of 12V.

When the mains power fails, diode D3 gets reverse biased and D4 gets forward biased so that the battery can automatically take up the load without any delay. When the battery voltage or input voltage alls below 10.5V, a cut-off circuit is used to prevent deep discharging of the battery. Resistor R3, zener diode ZD1 (10.5V) and transistor T2 form the cut-off circuit. When the voltage level is above 10.5V, transistor T2 conducts and its base becomes negative (as set by R3, VR2 and ZD1). But when the voltage reduces below 10.5V, the zener diode stops conduction and the base voltage of transistor T2 becomes positive. It goes into the ‘cut-off’ mode and prevents the current in the output stage. Preset VR2 (22k) adjusts the voltage below 0.6V to make T2 work if the voltage is above 10.5V.

When power from the mains is available, all output voltages—12V, 9V and 5V—are ready to run the load. On the other hand, when the mains power is down, output volt-ages can run the load only when the battery is fully charged (as indicated by LED1). For the partially charged battery, only 9V and 5V are available. Also, no output is available when the voltage goes below 10.5V. If battery voltage varies between 10.5V and 13V, output at terminal A may also vary between 10.5V and 12V, when the UPS system is in battery mode.

Outputs at points B and C provide 9V and 5V, respectively, through regulator ICs (IC1 and IC2), while output A provides 12V through the zener diode. The emergency lamp uses two ultra-bright white LEDs (LED2 and LED3) with current limiting resistors R5 and R6. The lamp can be manually switched ‘on’ and ‘off’ by S1. The circuit is assembled on a general purpose PCB. There is adequate space between the components to avoid overlapping. heat sinks for transistor T2 and regulator ICs (7809 and 7805) to dissipate heat are used.

The positive and negative rails should be strong enough to handle high current. Before connecting the circuit to the battery and transformer, connect it to a variable power supply. Provide 12V DC and adjust VR1 till LED1 glows. After setting the high voltage level, reduce the voltage to 10.5V and adjust VR2 till the output trips off. After the settings are complete, remove the variable power sup-ply and connect a fully-charged battery to the terminals and see that LED1 is on. After making all the adjustment connect the circuit to the battery and transformer. The battery used in the circuit is a 12V, 4.5Ah UPS battery.

Source : http://www.ecircuitslab.com/2012/05/mini-ups-system.html

Condenser Mic Audio Amplifier

The compact, low-cost condenser mic audio amplifier described here provides good-quality audio of 0.5 watts at 4.5 volts. It can be used as part of intercoms, walkie-talkies, low-power transmitters, and packet radio receivers. Transistors T1 and T2 form the mic preamplifier. Resistor R1 provides the necessary bias for the condenser mic while preset VR1 functions as gain control for varying its gain. In order to increase the audio power, the low-level audio output from the preamplifier stage is coupled via coupling capacitor C7 to the audio power amplifier built around BEL1895 IC.BEL1895 is a monolithic audio power amplifier IC designed specifically for sensitive AM radio applications that delivers 1 watt into 4 ohms at 6V power supply voltage. It exhibits low distortion and noise and operates over 3V-9V supply voltage, which makes it ideal for battery operation. A turn-on pop reduction circuit prevents thud when the power supply is switched on. Coupling capacitor C7 determines low-frequency response of the amplifier. Capacitor C9 acts as the ripple-rejection filter.

Condenser Mic Audio Amplifier Circuit Diagram

Capacitor C13 couples the output available at pin 1 to the loudspeaker. R15-C13 combination acts as the damping circuit for output oscillations. Capacitor C12 provides the boot strapping function. This circuit is suitable for low-power HAM radio transmitters to supply the necessary audio power for modulation. With simple modifications it can also be used in intercom circuits.

Source: http://www.ecircuitslab.com/2011/06/condenser-mic-audio-amplifier-circuit.html

Thursday, April 11, 2013

LIGHT ALARMS

LIGHT ALARM - 1
This circuit functions when light-weight|the solarshine} Dependent Resistor receives light. When no lightweight falls on the LDR, its resistance is excessive and in addition the transistor using the speaker isnt turned on. When lightweight falls on the LDR its resistance decreases and additionally the collector of the second transistor falls. This turns off the primary transistor rather via the 2nd 100n and additionally the initial 100n places a additional spike into the beneathside of the 2nd transistor. This continues until the 2nd transistor is turned on as onerous because it'll go. the main 100n is at present just about costd and it can't maintain the second transistor fliped on. The 2d transistor begins to show off and each and every transistors swap prerequisites to provide the second 1 of 2 of the cycle.

LIGHT ALARM - 2

This circuit is similar to light-weight Alarm -1 however produces a louder output on account of the speaker being connected straight away to the circuit. The circuit is essentially a excessive-gain amplifier thats fliped on at first with the support of the LDR after which the 10n maintains the circuit turning on till it's going to spark off no more. The circuit then begins to show off and sooner or later flips off completely. the current in the path of the LDR begins the cycle yet again.

LIGHT ALARM - three (MOVEMENT DETECTOR)

This circuit is intensely sensitive and is additionally positioned in a very space to realize the movement of an individual as so much as a pair of metres from the unit.

The circuit is essentially a excessive-gain amplifier (made of the primary 3 transistors) that is fliped on with the support of the LDR or photo Darlington transistor. The 0.33 transistor costs the 100u via a diode and this ships turn-on voltage for the oscillator. The LDR has equal sensitivity to the picture transistor right through this circuit.

Multitasking Pins Circuit

It’s entirely logical that low-cost miniature microcontrollers have fewer ‘legs’ than their bigger brothers and sisters – sometimes too few. The author has given some consideration to how to economise on pins, making them do the work of several. It occurred that one could exploit the high impedance feature of a tri-state output. In this way the signal produced by the high impedance state could be used for example as a CS signal of two ICs or else as a RD/ WR signal.

Circuit diagram:

multitasking pins circuit diagram

Multitasking Pins Circuit Diagram

All we need are two op-amps or comparators sharing a single operating voltage of 5 V and outputs capable of reaching full Low and High levels in 5-V operation (preferably types with rail-to-rail outputs). Suitable examples to use are the LM393 or LM311.The resistances in the voltage dividers in this circuit are uniformly 10 kilo ohms. Consequently input A lies at half the operating voltage (2.5 V), assuming nothing is connected to the input – or the microcontroller pin connected is at high impedance.

The non-inverting input of IC1A lies at two thirds and the inverting input of IC1B at one third of the operating voltage, so that in both cases the outputs are set at High state. If the microcontroller pin at input A becomes Low, the output of IC1B becomes Low and that of IC1A goes High. If A is High, everything is reversed.

source by :streampowers

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:

mall Audio Amplifier Circuit

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.

LIGHT ALARMS

LIGHT ALARM - 1
This circuit operates when lightweight|the sunshine} Dependent Resistor receives light. When no lightweight falls on the LDR, its resistance is high and also the transistor driving the speaker isnt turned on. When lightweight falls on the LDR its resistance decreases and also the collector of the second transistor falls. This turns off the primary transistor slightly via the second 100n and also the initial 100n puts a further spike into the bottom of the second transistor. This continues till the second transistor is turned on as onerous because it will go. the primary 100n is currently nearly charged and it cannot keep the second transistor turned on. The second transistor starts to turn off and each transistors swap conditions to provide the second half of the cycle.

LIGHT ALARM - 2

This circuit is comparable to lightweight Alarm -1 however produces a louder output as a result of the speaker being connected directly to the circuit. The circuit is essentially a high-gain amplifier thats turned on initially by the LDR and then the 10n keeps the circuit turning on till it will activate no more. The circuit then starts to show off and eventually turns off utterly. the present through the LDR starts the cycle once more.

LIGHT ALARM - 3 (MOVEMENT DETECTOR)

This circuit is extremely sensitive and may be placed in a very space to detect the movement of a person up to a pair of metres from the unit.

The circuit is essentially a high-gain amplifier (made of the primary 3 transistors) that is turned on by the LDR or photo Darlington transistor. The third transistor charges the 100u via a diode and this delivers turn-on voltage for the oscillator. The LDR has equal sensitivity to the photo transistor during this circuit.

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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.

VGA-to-BNC Adapter_165

VGA-to-BNC Adapter diagram_165

parts VGA-to-BNC Adapter_165

pcb VGA-to-BNC Adapter_165

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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