Isnin, April 15, 2013

70-260VAC to180-350VDC voltage Stabilzer


Using circuit diagram below can be built a voltage Stabilzer, able to convert a 70-260V AC to a 180-350V DC voltage.
For this, a rectifier contained in a MC34161 is used, as a voltage doubler for low input voltages and as rectifier for high standard input voltage.
A variation of four times of the input voltage is reflected in a variation of not more than two times in output voltage.
MC34161 has included a reference voltage source which supplies a voltage of 2.54 V to pin 1. The signal applied to pin 2 is compared with internal voltage of 1.27 V.
R2-R3 voltage divider provides change state of internal comparator which grow output input voltage over 135 V (pin 5 passes in 1 state). The potential at pin 2 is less than 1.27 V. Triac is blocked and disconnects median connection between the two output capacitors, C2 and C3, such that doubling output voltage can not be produced
70-260VAC to180-350VDC voltage converter
  • When the input voltage is less than 135 V, pin 2 is maintained above the potential value of 1.27 V
  • Diodes D2 and D3 and capacitors C2 and C3 will function as voltage doubler.
  • Zener diode D5, together with R1 and C4, integrated circuit provides power to a stable source of 12 V. The time required passing standard rectifier circuit of the voltage doubler is determined by R4-C1.
  • Operating voltage of capacitors C2 and C3 must be> 250 V.

12VDC to 220V 50Hz 500W Inverter Circuit


This is circuit Inverter 12VDC to 220V 50Hz 500W.
It easy to make and Low cost. Friends favorite circuit about the the inverter, because like working outdoors, or to backup storage to use when necessary. Most of this is circuit low power, which is not suitable for practical applications. My friends said that he would be about 500 Watt.
It is a good size. Use with television receivers and light bulbs as well. When looking for circuit. I get headaches. If you are a beginner or I can not buy expensive good quality circuits. Requires only one transistor. Or if you have free time. I want to build old circuit is alive again. This circuit will accommodate all your needs. It is a simple circuit. 
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZC38unjeX-vPbjuvl_ZjayIojvqYNMRmvUDzkMTVbBFq0EZqN4W4m2LdV2mBO147D7LiHJeGXEnItnyKei1imocZRXJ-WIL0hhoznw8iJ_ykCiJTHHEKpLCMtpIGFZbdEr0I_rpO06gYM/s1600/Inverter+12VDC+to+220V+50Hz+500W.jpg




The same principle, I take battery voltage 12V to produce a oscillator about 100 Hz and pass to a two frequency divider circuit is only 50HZ. And drive a 10 ampere transformer with 10 x 2N3055 transistor in parallel. By a single transistor has 2A, when I use 10 transistors or 5 pairs of drive high current output. The complexity of circuit, but the principle is not it, and it is the number of transistors on a basic, easy to buy. You may be modified 100 watt power inverter To the size of transistors and transformers as well.
Source:circuitschematicelectronics

Inverter DC9V to AC13.5kV Circuit Diagram


Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.


9V to 13.5kV Inverter Circuit


This high voltage source is formed by an inverter, around the transistor, which provides pulses of 150V to the inverter formed by the thyristor and capacitor in series with the transformer 2. This pulse output of 4.5kV to be multiplied with the network so as to achieve the output voltage of 13.5kV.  Neon lamps (marked LN) form the thyristor triggering pulses.
The transformer T1 has a ratio 3000:500 Ω of the type used in audio output transistor. T2 is a transformer flash lamp trigger a secondary 6kV. This inverter circuit requires a 9VDC power supply with current 0.01A

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQt41nooiyy2YfKKqDTSHqLvUNhY4eBdVpCiZ42B80CIc26hgFuxIVqJ5AfMJxPG8I0kNaXKF0cv7lGULtMOdHx9T6EpgyVF2bZjeSnfZzXA475dz5O1C1QYc1qEXQvzg2e_WFXzgsYMCb/s1600/9V+to+13.5kV+Inverter.jpg

Caution:
Apply this equipment on the human body can cause serious physical injury to death. Don’t use in humans.

High voltage inverter

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.

3V to High voltage inverter

Inverter circuit on basic of really taking a series of mosquito racket, a racket in which these mosquitoes require only a low voltage. With only 3 Volts course of this series has been able to work. Circuit is raising the voltage by a transformer that can be made yourself with the need of copper wire and ferrite rods.


https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3i3nJfPywtbLldwSnSBWbgqIDDK7h1UzKWunNakNxHYlIJ3OA0s_5nitj34AhKgjKxY0dTfiiz30bED4SbQO5Gm7LLRxi7jaXCVJYbJqB4281XFm4Lj3LPhDj4XAncOS0Vz_HzQ_nOc-z/s1600/High+Voltage+Inverter+schematic.jpg


How to making a transformer like that here, but this circuit requires a step-up transformer that are larger and require a lot of coils. This transformer is controlled by a transistor semiconductor 24D506 in this series. To output issued until 1KV or more but issued is very low current (microampire). This circuit can also be used in fluorescent lamps 10W maximum. When used in fluorescent lamps add another capacitor to the voltage for provoke can turn on the lights.

Part List :

Resistor
R1____1K5 Ω
R2____4K3 Ω
R3____22M Ω

Capacitor
C1____100n
C2____100n  400V
C3____0.2uF 400V


Diode
D1___1N4007
D2___1N4007

Transistor
Q1___ 24D506

Transformer
L1___#100 turns
L2___#100 turns
L3___#1000 turns



https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvQ08hY5qq-oqncFmOjM-5ZohRBEDEUZ_XJFwb5YxHPSJzf-u2eksDz2Xt4026dPccEmz4Nqs4pBjCUjKHqegbtNanOTgJ4fFGf0hLRI9AacFwRewyIyD1OE7l62Lt5skSTF1V8HWa-iHZ/s1600/IMG0160A.jpg





5000W DC to AC Inverter

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical





Inverter 5000 Watt 

This inverter uses PWM (Pulse Width Modulator) with type IC SG3524. IC serves as a oscillator 50Hz, as a regulator of the desired output voltage. Input power ranging from 250W up to 5000W output and has. Following a series INVERTER 5000W with PWM (Pulse Width Modulator).
 
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiIvBj8Eh4k-fIbv64PZc-O34zaxOdWLS4MkwFGKbTlZhwsKTDBhD8YV-Q2z2WMBoYLUe2sNlGPbYkAJ_2dS07xu4MNS2CxQ1ZCiAhXCm15bLrzeYtRgj20Y05lHswXuJE1wWgYmXPmbTCT/s1600/Inverter+PWM+5000W.png
Schematic Inverter 5000W with PWM (Pulse Width Modulator)


below is the output power settings that can be issued by this inverter:

DC voltage and Transformer "T2" winding recommendation:

Winding Power Supply

12VDC 750W P: 24V "12-0-12" / S: 220V

1500W 24VDC P: 48V "24-0-24" / S: 220V

2250W 36VDC P: 72V "36-0-36" / S: 220V

3000W 48VDC P: 96V "48-0-48" / S: 220V

3750W 60VDC P: 120V "60-0-60" / S: 220V

4500W 72VDC P: 144V "72-0-72" / S: 220V

5250W 84VDC P: 168V "84-0-84" / S: 220V


Transformer used is the transformer CENTER TAP

R1 serves to regulate the voltage to 220v inverter

R2 serves to regulate the inverter output frequency of 50 or 60 Hz (as appropriate)
 

Sabertooth Dual Motor Speed Controllers

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.



Sabertooth 2X12 R/C is a dual motor driver specifically optimized for use in radio controlled vehicles. It is suitable for medium powered robots, cars and boats. The Sabertooth 2x12 RC replaces our 2x10 RC controller.



Out of the box, it can supply two DC brushed motors with up to 12A each. Peak currents of 25A are achievable for a few seconds. Overcurrent and thermal protection means you'll never have to worry about killing the driver with accidental stalls or by hooking up too big a motor.


This special R/C edition of our motor driver comes with options for exponential control, autocalibration and built-in mixing. The operating mode is set with the onboard DIP switches so there are no jumpers to lose.


Sabertooth is the first synchronous regenerative motor driver in its class. The regenerative topology means that your batteries get recharged whenever you command your robot to slow down or reverse. Sabertooth also allows you to make very fast stops and reverses - giving your vehicle a quick and nimble edge.


Sabertooth has a built in 5V Switching BEC that can provide power to a microcontroller or R/C receiver and a servo or two. The lithium cutoff mode allows Sabertooth to operate safely with lithium ion and lithium polymer battery packs - the highest energy density batteries available.


Sabertooth's transistors are switched at ultrasonic speeds (32kHz) for silent operation.


1 Amp Switching BEC - Can now power your receiver and multiple servos


12 Amp Continuous/25A Peak Power Rating - A redesigned power stage increases current handling capabilities


Acceleration Ramping - Selectible by DIP switches. Replaces the flip function.


6.0 - 25.0V input
Current handling up to 18V12 amps continuous, 25A Peak per channel
Current handling at 24V10 amps continuous, 12A continuous with airflow, 25A peak per channel
Size2.3" x 1.8" x 0.75"
Weight1.5 oz (43g)
Synchronous regenerative driveyes
Ultra-sonic switching frequencyyes
Thermal and overcurrent protectionyes
Lithium protection modeyes
Here is a great DIP switch wizard that will help you configure your Sabertooth.

555 FUEL INJECTION SYSTEM

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.  


The Wright Brothers 1903 aircraft piston engine fuel flowed through a small metal fuel line from the high mounted tank to the engine. The fuel dripped into a flat, enclosed pan that sits on the top of the engine. The floor of the pan was hot because it sat over the hot engine cylinders. Air was drawn into the pan through the air intake, because of the action of the pistons. The combination of air being drawn over the fuel and the heat of the floor of the pan caused the gasoline to evaporate.


The fuel flow to the engine was adjusted while the aircraft was waiting on the launch rail. When the engine was running as fast and smooth as possible the aircraft was ready for launch. The pilot had a control lever which was connected to a cut-off valve to stop the engine at the end of the flight. The brothers had no throttle or engine control during the 1903 flights. The Wright "carburetor" and intake system had no moving parts. Without the moving parts, the brothers engine ran at just one speed throughout the flights of 1903.


My hangar neighbor Klaus Saviour's O-200 engine also runs with a constant speed dribble system consisting only of one small tube, poked into the throttle body, gravity feeding fuel from a header tank and using a fixed throttle opening and at a given RPM. He uses it as a back up system to his 555 integrated circuit based EFI.




Here is what a similar emergency system would look like for a two rotor Mazda p-port engine.


Airplane engines are different from car engines. Unlike car engines they have a known and repetitive load verses RPM curve using a fixed pitch prop. There are no requirements for rapid acceleration or rapid changes in load or RPM. Consequently the fuel system can be very rudimentary. In a car engine it is possible to have high RPM with low fuel flow if there is no load on the engine. You don't see that in aircraft engines with fixed pitch props. Load is probably proportional only to RPM squared when driving a prop when tip speeds are below the transonic range. At that point the load approaches very high values indeed.


The hot wire mass airflow sensor is probably the most ubiquitous way to control an automotive EFI system. It automatically compensates for humidity and intake air temperature unlike a manifold pressure sensor. You do need the e-shaft trigger but the mass air flow sensor can control the pulse width while the e-shaft triggers the injector once per revolution. Unfortunately it is not a linear device. It takes a computer to deal with it's voltage output as a function of the mass air flow through it. For that reason we are not going to use it with this system. Instead we will use manifold pressure to control a 555.

The 555 is a small and cheap integrated circuit implementing a variety of timer and multi-vibrator applications. The IC was designed and invented by Hans R. Camenzind in 1970. The original was called "The IC Time Machine". It is still in wide use, thanks to its ease of use, low price and good stability. As of 2003 one billion units are manufactured every year.


The 555 timer is one of the most popular and versatile integrated circuits ever produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in an 8-pin mini dual-in-line package. Also available from TI are ultra-low power versions of the 555 such as the TLC555. This one works the best and it will be the one we are going to use. No other one, that I have found, works nearly as well. In essence, what the EFI computer does is gather data from its sensors and then use that data to to determine an injector pulse width. The TLC555 can do the same thing in a simple and cheap $1 chip.


The TLC555 has a pulse width modulation mode that works very well. In essence it is a complete EFI system for less than $1. One TLC555 per injector. If one fails no big deal.

This next chart from Paul Yaw shows the wider dynamic range of the more modern fuel injectors. The purple line. The delay on the lower end is the dead time.Earlier Mazda injectors had a longer dead time so it was necessary to use staged injectors. In other words one injector per rotor at low power and a two injectors per rotor at higher powers. I don't think that is now necessary for aircraft use. Also idle and low RPM with car use precise fuel control was very important to to emissions requirements.


The main sensor required is the intake manifold pressure.


The TLC555 can change the amount of fuel over a nine to one range at 6000 RPM as the pulse width varies from 1 msec to 9.5 m sec as the signal from the mass airflow sensor changes its output voltage from zero to five volts. A bonus for the TLC 555 chip is it's high output drive current of 15 ma source and 150 ma sink on pin 3. It is not your grandfather's 555 or even your dad's for that matter. That should be enough to drive the injector FET directly and it was.


I am talking about a complete TLC555 based EFI system costing less than 100 dollars while the cheapest micro computer system, the Megasquirt, is over $300 (completely assembled). Tracy Crook's dual system is over $750 and many, like the Haltech, are over $1000. Plus the TLC555 EFI is a super simple system and anybody that anybody can fix or build from scratch. No need to learn programming or guess what a proprietary EFI software program is trying to do. There is no software. Suitable carburetor's are over $1000.
Here is the skematic.




You don't need a degree in computer science or electronics to understand it or fix it. Any mechanic or electronics technician should be able to build and fix it. It is organized as three simple and reliable systems. Simple manual controls in the form of switches help diagnose the system and give flexibility of use.


The Trigger system conditions the pulse from the e-shaft position sensors and feeds it to the Injector driver. Only one trigger system is require per rotor. More than one trigger system can be implemented for redundancy as this is a true modular system with stand alone capabilities.


The Injector Driver system contains the TLC 555 and a transistor to turn the injector on and off. One or two can be used per rotor. If two are used per rotor and the engine is two rich at idle one per rotor can be turned off with the addition of two switches. Smooth running at low RPM is seldom required of an aircraft engine. Newer injectors have a wider dynamic range so smooth running is still possible with four injectors. In other words the minimum amount of fuel injected has been extended downward. We will find out when we test various injectors.


The Leaning System is used to lean the engine at cruise. One per rotor can be used to adjust the mixture on each rotor separately. You don't have to use one per rotor if you don't want to. One unit can lean all injectors. Its output is connected to pin 5 of the TLC555 to control the pulse width. It get's its input information voltage from the mass airflow sensor. We would set up the TLC 555 pulse width in an aircraft engine to be rich all the time for engine acceleration purposes. No need for an accelerator pump. Many aircraft engine carbs don't have them. Once you reach cruise you lean the mixture to as little as 18:1 for best BSFC.


There are two sensors on the e-shaft steel trigger plate 180 degrees out... one for each rotor. The angular position of the sensors control when the fuel is injected. Here are a couple of stock Mazda triggers.

Also note it is simple to adapt this system to a three or four rotor engine. Just replicate the systems as needed. This is an e-shaft trigger mounted on Mark Steitle's three rotor powered Lancair ES. The trigger wheel shown is not the right one for this system.

Test set up for magnetic trigger.

As you can see all I used is a simple bar of steel about 6 inches long 3/4 inch wide and 1/8th inch thick. This is to trigger the 555 fuel injectors. It can be rotated on the e-shaft pulley to set the injector timing anywhere. The scope is set at 5 volts per vertical division and 10 ms per horizontal division.



At 1500 RPM it is still - 30 volts which is more than enough to trigger the 555. A simple full wave bridge is used that only requires four low cost diodes.


The ideal trigger tooth is about 1/4 to 3/8 thick (wide) and comes to a sharp point. The spacing must be .050 or less. The amplitude of the trigger pulse is a very VERY strong function of the spacing. 0.010 will make a HUGE difference.


I would use a feeler gage to set it.


There will be only one trigger tooth and four mag pickups. Two for ignition (about 22 degrees BTDC) and two for fuel injection (about 90 degrees BTDC). The angular position of the pickup relative to top dead center will adjust the timing of both 555 fuel injection and ignition.


A fuel injector is nothing more than an electronically controlled valve. It is supplied with pressurized fuel by the fuel pump and it is capable of opening and closing many times per second. The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width. Injectors are classified into two categories.


High coil resistance (saturated) 12-16 Ohms.


Low coil resistance (peak & hold) 0.5-6 Ohms.


Saturated injectors require roughly 1-1.5 amps to open the injector. Peak & hold injectors initially needs about 4-6 amps, and once open drops to roughly 2-3 amps to keep it open. This system uses the high coil resistance injectors to keep it simple. With four injectors and a P-port engine you will need injectors capable of feeding about 75 Horses each.


Fuel Injector flow rates compiled by steve@aems.com.au


Injectors listed by max flow rate, from lowest to highest



Conversion From cc per min to lbs per hour to HP. 500cc per minute is approximately equal to 49lbs per hour which is equal to approximately 100 HP.


Common conversions

lbs/hour = cc per minute / 10.2


lbs per hour = HP / 2.04


cc per minute = lbs per hour x 10.2


cc per minute = HP x 5


HP = cc per minute / 5


HP = lbs per hour x 2.04


Note: This is a rough guide for conversions and flow rates. If you have any information that would help in increasing the quality of this data base, please send email to steve@aems.com.au.


I really like the small diameter of the RX8 injectors. They may not flow enough for a p-port engine however. Two can be mounted side by side on a 2 inch P-port intake tube.


Here is what the 250 HP p-port installation looks like.

Here is what the p-port installation looks like with the mandatory air box plenum. If you don't do this tuned intake system spit back fuel vapor and it can be a fire hazard. See UTUBPLEASE for a Youtube video of a p-port RX8 engine running on a dyno showing the spit back.
One of the problems most people are confronted with is obtaining connectors. There appears to be no standardized fuel injector connectors. Here are a couple of examples.



Here is a way around it. These are Molex female sockets used in just about every PC in the world to connect the power supply to the mother board. Electronic stores like Fry's sells them for about $1 a dozen. solder them to the wires and use a bit of heat shrink tubing. When you are ready to fly you can put a dab of red RTV in the socket to hold them in. If you grease the walls of the socket you might get lucky and have your own custom injector plugs after the red RTV hardens.








Sabtu, April 13, 2013

Romote Control Switch

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.





RC (Remote Control) Switch





It is sometimes necessary for an RC (remote control) model to contain some kind of switching functionality. Some things that come to mind are lights on a model boat, or the folding away of the undercarriage of an aeroplane, etc. A standard solution employs a servo, which then actually operates the switch. Separate modules are also available, which may or may not contain a relay. A device with such functionality is eminently suitable for building yourself. The schematic shows that it can be easily realised with a few standard components.

Picture of the project:
RC Switch Circuit
The servo signal, which consists of pulses from 1 to 2 ms duration, depending on the desired position, enters the circuit via pin 1 of connector K1. Two buffers from IC2 provide the necessary buffering after which the signal is differentiated by C2. This has the effect that at each rising edge a negative start signal is presented to pin 2 of IC1. D1 and R4 make sure that at the falling edge the voltage at pin 2 of IC2 does not become too high. IC1 (TLC555) is an old faithful in a CMOS version. A standard version (such as the NE555) works just as well, but this IC draws an unnecessarily high current, while we strive to keep the current consumption as low as possible in the model. The aforementioned 555 is configured as a one-shot. The pulse-duration depends on the combination of R2/C1. Lowering the voltage on pin 5 also affects the time. This results in reducing the length of the pulse. In this circuit the pulse at the output of IC will last just over 1.5 ms when T1 does not conduct.



Circuit diagram:
RC Switch Circuit Diagram

When T1 does conduct, the duration will be a little shorter than 1.5 ms. We will explain the purpose of this a little later on. Via IC2.C, the fixed-length pulse is, presented to the clock input of a D-flip-flop. As a consequence, the flip-flip will remember the state of the input (servo signal). The result is that when the servo-pulse is longer than the pulse form the 555, output Q will be high, otherwise the output will be low. It is possible, in practice, that the servo signal is nearly the same length as the output from the 555. A small amount of variation in the servo signal could therefore easily cause the output to ‘chatter’, that is, the output could be high at one time and low the next. To prevent this chatter there is feedback in the form of R1, R3 and T1. This circuit makes sure that when the flip-flip has decided that the servo-pulse is longer than the 555’s pulse (and signals this by making output Q high), the pulse duration from the 555 is made a little shorter. The length of the servo-signal will now have to be reduced by a reasonable amount before the servo-pulse becomes shorter than the 555’s pulse.

Parts and PCB layout
:
The moment this happens, T1 will stop conducting and the mono-stable time will become a little longer. The servo-pulse will now have to be longer by a reasonable amount before the flip-flip changes back again. This principle is called hysteresis. Jumper JP1 lets you choose between the normal or inverted output signals. Buffers IC2.D through to IC2.F together with R5 drive output transistor T2, which in turn drives the output. Note that the load may draw a maximum current of 100 mA. Diode D2 has been added so that inductive loads can be switched as well (for example, electrically operated pneu-matic valves).



COMPONENTS LIST:

Resistors: R1 = 470k

R2 = 150k

R3 = 47k

R4 = 100k

R5 = 4k7

Capacitors:

C1 = 10nF

C2 = 1nF

C3,C4 = 100nF

Semiconductors:

D1 = BAT85 or similar Schottky diode

D2 = 1N4148

IC1 = CMOS 555 (e.g., TLC555 or ICM7555)

IC2 = 4049

IC3 = 4013

T1,T2 = BC547B

Miscellaneous: JP1 = jumper with 3-way pinheader

K1 = servo cable

K2 = 2-way pinheader or 2 solder pins
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COLLEGE QUIZ BUZZER


Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.





Manual buzzers used for quiz competitions in schools and colleges create a lot of confusion in identifying the first respondent. Although there are circuits using PCs and discrete ICs, they are either too expensive or limited to only a few number of players. The quiz buzzer circuit given here can be used for up to eight players, which is maximum in any quiz competition. The circuit uses IC 74LS373 and a few passive components that are readily available in the market. The circuit can be divided into two sections: power supply and quiz buzzer.
Fig. 1 shows the power supply section. The regulated 5V power supply for the quiz buzzer section is derived from AC mains. The 230V AC mains is stepped down to 7.5V AC by transformer X1, rectified by bridge rectifier BR1, filtered by C1 and regulated by regulator IC1. Capacitor C2 bypasses ripples in the regulator output.
Fig. 2 shows the quiz buzzer section. At the heart of this section is IC 74LS373, an octal latch that is used to transfer the logic state at data input pins D0 through D7 to the corresponding Q0 through Q7 outputs. Data pins D0 through D7 are normally pulled low by resistors R1 through R8, respectively.
One terminal of push-to-on switches S1 through S8 is connected to +5V, while the other terminal is connected to the respective data input pins. The switches are to be extended to the players through cord wire. The torch bulbs BL1 through BL8 can be housed in boxes with the front side of the boxes covered with a white paper having the name or number of the contestant written over it for easy identification. Place the boxes above the head level so that these can be seen by the audience also. When the power is switched on using switch S9 (provided terminals ‘A’ and ‘B’ of both the power supply and quiz buzzer sections are interconnected), the circuit is ready to use. Now all the switches (S1 through S8) are open and Q0 through Q7 outputs of IC 74LS373 are low. As a result, the gates of silicon-controlled rectifiers SCR1 through SCR8 are also low.
As soon as a contestant momentarily presses his respective switch, the corresponding output data pin goes high. This triggers the corresponding SCR and the respective bulb glows. At the same time, the piezobuzzer (PZ1) sounds as transistor T1 conducts. Simultaneously, the base of transistor T2 becomes high to make it conduct. Latch-enable (LE) pin 11 of IC2 is tied to ground to latch all the Q0 through Q7 outputs. This restricts further change in the output state due to any change in the state of switches S1 through S8 by any other contestant. Only one of the eight torch bulbs glows until the circuit is reset by on/off switch S9. Note. The complete kit is available at Kits ‘n’ Spares outlet.



SPEED CHECKER FOR HIGHWAYS

Speed Checker for Highways
While driving on highways, motorists should not exceed the maximum speed limit permitted for their vehicle. However, accidents keep occurring due to speed violations since the drivers tend to ignore their speedometers. This speed checker will come handy for the highway traffic police as it will not only provide a digital display in accordance with a vehicle’s speed but also sound an alarm if the vehicle exceeds the permissible speed for thehighway. The system basically comprises two laser transmitter-LDR sensor pairs, which are installed on the highway 100 metres apart, with the transmitter and the LDR sensor of each pair on the opposite sides of the road. Theinstallation of lasers and LDRs is shown in Fig. 1. The system displays the time taken by the vehicle in crossing this 100m distance from one pair to the other with a resolution of 0.01 second, from which the speed of the vehicle can be calculated as follows:
As per the above equation, for a


speed of 40 kmph the display will read 900 (or 9 seconds), and for a speed of 60 kmph the display will read 600 (or 6
seconds). Note that the LSB of the display equals 0.01 second and each succeeding digit is ten times the preceding digit. You can similarly calculate the other readings (or time).
Circuit description
Fig. 2 shows the circuit of the speed checker. It has been esigned assuming that the maximum permissible speed for highways is either 40 kmph or 60 kmph as per the traffic rule.
The circuit is built around five NE555 timer ICs (IC1 through IC5), four CD4026 counter ICs (IC6 through IC9) and four 7-segment displays (DIS1 through DIS4). IC1 through IC3 function as monostables, with IC1 serving as count-start mono, IC2 as count-stop mono and IC3 as speed-limit detector
mono, controlled by IC1 and IC2 outputs. Bistable set-reset IC4 is also controlled
by the outputs of IC1 and IC2 and it (IC4), in turn, controls switching on/off of the 100Hz (period = 0.01 second) astable timer IC5.
The time period of timer NE555 (IC1) count-start monostable multivibrator is adjusted using preset VR1 or VR2 and capacitor C1. For 40kmph limit the time period is set for 9 seconds using preset VR1, while for 60kmph limit the time period is set for 6 seconds using preset VR2. Slide switch S1 is used to select the time period as per the speed limit (40 kmph and 60 kmph, respectively). The junction of LDR1 and resistor R1 is coupled to pin 2 of IC1.
Normally, light from the laser keeps falling on the LDR sensor continuously and thus the LDR offers a low resistance and pin 2 of IC1 is high. Whenever light falling on the LDR is interrupted by any vehicle, the LDR resistance goes high and hence pin 2 of IC1 goes low to trigger the onostable.
As a result, output pin 3 goes high for the preset period (9 or 6 seconds) and LED1 glows to indicate it. Reset pin 4 is controlled by the output of NAND generator IC5. IC5 can also be reset via diode D2 at power-on as well as when reset switch S2 is pressed. IC5 is configured as an astable multivibrator whose time period is decided by preset VR3, resistor R12 and capacitor C10. Using preset VR1, the frequency of the astable multivibrator is set as 100 Hz. The output of IC5 is fed to clock pin 1 of decade counter/7- segment decoder IC6 CD4026. gate N3 at power-on or whenever reset switch S2 is pushed. For IC2, the monostable is triggered in the same way as IC1 when the vehicle intersects the laser beam incident on LDR2 to generate a small pulse for stopping the count and for use in the speed detection. LED2 glows for the duration for which pin 3 of IC2 is high.
The outputs of IC1 and IC2 are fed to input pins 2 and 1 of NAND gate N1, respectively. When the outputs of IC1 and IC2 go high simultaneously (meaning that the vehicle has crossed the preset speed limit), output pin 3 of gate N1 goes low to trigger monostable timer IC3. The output of IC3 is used for driving piezobuzzer PZ1, which alerts the operator of speed-limit violation. Resistor R9 and capacitor C5 decide the time period for which the piezobuzzer
sounds. The output of IC1 triggers the bistable (IC4) through gate N2 at the leading edge of the count-start pulse. When pin 2 of IC4 goes low, the high output at its pin 3 enables astable clock
generator IC5. Since the count-stop pulse output of IC2 is connected to pin 6 of IC4 via diode D1, it resets clock IC CD4026 is a 5-stage Johnson decade counter and an output decoder that converts the Johnson code into a 7-segment decoded output for driving DIS1 display. The ounter advances by one count at the positive clock signal transition. The carry-out (Cout) signal from CD4026 provides one clock after every ten clock inputs to clock the succeeding decade counter in a multidecade counting chain. This is achieved by connecting pin 5 of each CD4026 to pin 1 of the next CD4026.
A high reset signal clears the deFig. 3: Power supply Fig. 4: Actual-size, single-side PCB layout for the speed checker Fig. 5: Component layout for the PCB Construction 62
cade counter to its zero count. Pressing switch S2 provides a reset signal to pin 15 of all CD4026 ICs and also IC1 and IC4. Capacitor C12 and resistor R14 generate the power-on-reset signal.
The seven decoded outputs ‘a’ through ‘g’ of CD4026s illuminate the proper segment of the 7-segment displays (DIS1 through DIS4) used for representing the decimal digits ‘0’ through ‘9.’ Resistors R16 through R19 limit the current across DIS1 through DIS4, respectively.
Fig. 3 shows the circuit of the power supply. The AC mains is stepped down by transforme X1 to deliver the secondary output of 15 volts, 500 mA. The transformer output is rectified by
a bridge rectifier comprising diodes D3 through D6, filtered by capacitor C14 and regulated by IC11 to provide regulated 12V supply. Capacitor C15 bypasses any ripple in the regulated
output. Switch S3 is used as the ‘on’/ ‘off’ switch. In mobile application of the circuit, where mains 230V AC is not available, it is advisable to use an external 12V battery. For activating the lasers used in conjunction with LDR1 and LDR2, separate batteries may be used.

Construction and working
Assemble the circuit on a PCB. An actual-size, single-side PCB layout for the speed checker is shown in Fig. 4 and its component layout in Fig. 5. Before operation, using a multimeter check whether the power supply output is correct. If yes, apply power supply to the circuit by flipping switch S3 to ‘on.’ In the circuit, use long wires for connecting the two LDRs, so that you can take them out of the PCB and install on one side of the highway,
100 metres apart. Install the two laser transmitters (such as laser torches) on the other side of the highway exactly opposite to the LDRs such that laser  light falls directly on the LDRs. Reset  the circuit by pressing switch S2, so the  display shows ‘0000.’ Using switch S1,  select the speed limit (say, 60 kmph) for  the highway. When any vehicle crosses
the first laser light, LDR1 will trigger  IC1. The output of IC1 goes high for  the time set to cross 100 metres with  the selected speed (60 kmph) and LED1  glows during for period. When the vehicle crosses the second laser light, the output of IC2 goes high and LED2
glows for this period. Piezobuzzer PZ1 sounds an alarm if the vehicle crosses the distance between the laser set-ups at more than the selected speed (lesser period than preset
period). The counter starts counting when the first laser beam is intercepted and stops when the second laser beam is intercepted. The time taken by the  vehicle to cross both the laser beams is displayed on the 7-segment display. For 60kmph speed setting, with timer frequency set at 100 Hz, if the display count is less than ‘600,’ it means that the
vehicle has crossed the speed limit (and simultaneously the buzzer sounds). Reset the circuit for monitoring the speed of the next vehicle. 

Note. This speed checker can check the speed of only one vehicle at a time.