Description:
This circuit provides a delayed visual indication when a door bell switch is pressed. In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch. The lamp can illuminate the words "Please Wait" for anyone with walking difficulties.

Working:
The circuit uses standard 2 wire doorbell cable or loudspeaker wire. In parallel with the doorbell switch, S1, is a 1N4001 diode and a 12 volt 60mA bulb. The bulb is optional, it may be useful for anyone who is slow to answer the door, all you need to do is flick a switch inside the house, and the bulb will illuminate a label saying Please Wait inside the doorbell switch or close to it. The double pole double throw switch sends the doorbell supply to the lamp, the 22 ohm resistor is there to reduce current flow, should the doorbell switch, S1 be pressed while the lamp is on. The resistor needs to be rated 10 watts, the 0.5 Amp fuse protects against short circuits.
When S2 is in the up position (shown as brown contacts), this will illuminate the remote doorbell lamp. When down, (blue contacts) this is the normal position and will illuminate the lamp inside the house. Switch S1 will then charge the 47u capacitor and operate the transistor which lights the lamp. As a door bell switch is only pressed momentarily, then the charge on the capacitor decays slowly, resulting in the lamp being left on for several seconds. If a longer period is needed then the capacitor may be increased in value.

An infra-red or wireless remote control has the disadvantage that the small, handy, remote (transmitter) is often misplaced. The sound operated switch has the advantage that the transmitter is always with you. This project offers a way to control up to four latching switches with two claps of your hand. These switches may be used to control lights or fans—or anything else that does not produce too loud a sound.
To prevent an occasional loud sound from causing malfunction, the circuit is normally quiescent. The first clap takes it out of standby state and starts a scan of eight panel-mounted LEDs. Each of the four switches are accompanied with two LEDs—one for indicating the ‘on’ and the other for indicating the ‘off’ state. A second clap, while the appropriate LED is lit, activates that function.For example, if you clap while LED10 used in conjunction with Lamp 1 is lit then the lamp turns on. (If it is already on, nothing happens and it remains on.)
A condenser microphone, as used in tape recorders, is used here to pick up the sound of the claps. The signal is then amplified and shaped into a pulse by three inverters (N1 through N3) contained in CMOS hex inverter IC CD4069. A clock generator built from two of the inverter gates (N5 and N6) supplies clock pulses to a decade counter CD4017 (IC2). Eight outputs of this IC drive LEDs (1 through 8). These outputs also go to the J and K inputs of four flip-flops inside two CD4027 ICs (IC3 and IC4). The clock inputs of these flip-flops are connected to the pulse shaped sound signal (available at the output of gate N3).
Additional circuitry around the CD4017 counter ensures that it is in the reset state, after reaching count 9, and that the reset is removed when a sound signal is received.
Outputs of the four flip-flops are buffered by transistors and fed via LEDs to the gates of four triacs. These triacs switch the mains supply to four loads,usually lamps. If small lamps are to be controlled, these may be directly driven by the transistors.
If this circuit is to be active, i.e.scanning all the time, some components around CD4017 IC could be omitted and some connections changed. But then it would no longer be immune to an occasional,spurious loud sound.
The condenser microphone usually available in the market has two terminals.It has to be supplied with power for it to function. Any interference on this supply line will be passed on to the output. So the supply for the microphone is smoothed by resistor-capacitor combination of R2, C1 and fed to it via resistor R1.
CD4069, a hex unbuffered inverter,contains six similar inverters. When the output and input of such an inverter is bridged by a resistor, it functions as an inverting amplifier. Capacitor C2 couples the signal developed by the microphone to N1 inverter in this IC, which is configured as an amplifier. The output of gate N1 is directly connected to the input of next gate N2. Capacitor C3 couples the output of this inverter to N3 inverter,which is connected as an adjustable level comparator. Inverter N4 is connected as an LED (9) driver to help in setting the sensitivity.
Preset VR1 supplies a variable bias to N3. If the wiper of VR1 is set towards the negative supply end, the circuit becomes relatively insensitive (i.e. requires a thunderous clap to operate). As the wiper is turned towards resistor R4,the circuit becomes progressively more sensitive. The sound signal supplied by gate N2 is added to the voltage set by preset VR1 and applied to the input of gate N3. When this voltage crosses half the supply voltage, the output of gate N3 goes low. This output is normally high since the input is held low by adjustment of preset VR1.
The output of gate N3 is used for two things: First, it releases the reset state of IC2 via diode D1. Second, it feeds the clock inputs to the four flip-flops contained in IC3 and IC4. In the quiescent state, IC2 is reset and its ‘Q0’ output is high. Capacitor C4 is charged positively and it holds this charge due to the connection from R5 to this output (Q0).
IC2 is a decade counter with fully decoded outputs. It has ten outputs labelled Q0 to Q9 which go successively high, one at a time, when the clock input is fed with pulses. IC3 and IC4 are dual JK flip-flops. In this circuit they store (latch) the state of the four switches and control the output through transistors and triacs. At the first clap, the output of gate N3 goes low and diode D1 conducts, discharging capacitor C4. The reset input of IC2 goes low, releasing its reset state.
All the J and K inputs of the four flipflops are low and so these do not change state, even though their clock inputs receive pulses.When the reset input of IC2 is low, each clock pulse causes IC2 to advance by one count and its outputs go high successively,lighting up the corresponding LEDs and pulling high the J and K inputs of the four flip-flops, one after the other. Resistor R8 limits the current through LEDs 1 through 8 to about 2 mA. Larger current might cause malfunction due to the outputs of IC2 being pulled down below the logic 1 state input voltage.
If a second clap is detected while the J input of a particular flip-flop is high, its Q output will go high, regardless of what state it was in previously.Similarly, if its K input was high, the output will go low. (If both J and K are high, the output will change state at each clock pulse.) Thus although all flip-flops receive the clap signal at their clock inputs, only the one selected by the active output of IC2 will change state. Resistor R9 and capacitor C6 ensure that the flip-flops start in the off state when power to the circuit is switched on, by providing a positive power-on-reset pulse to the reset input pins when power is applied. The preset input pins are not used and are therefore connected directly to ground.
When, after eight clock pulses, output Q8 of IC2 becomes high, diode D2 conducts, charging capacitor C4, thereby resetting IC2 and making its Q0 output high. And there it stays, awaiting the next clap.The four Q outputs of IC3 and IC4 are buffered by npn transistors, fed through current limiting resistors and LEDs (to indicate the on/off state of the loads) to the gates of four triacs. Four lamps operating on the mains may thus be controlled. For demonstrations, it might be better to drive small lamps (drawing less than 100 mA at 12V) directly from the emitters of the transistors. In this case the triacs, LEDs and their associated current limiting resistors may be omitted.
It has to be noted that one side of the mains has to be connected to the negative supply line of this circuit when mains loads are to be controlled. This necessitates safe construction of the circuit such that no part of it is liable to be touched.The advantage is that it may be mounted out of reach of curious hands since it does not need to be handled during normal operation. It is advisable to start with the low voltage version and then upgrade to mains operation, once you are sure everything else is working satisfactorily.CMOS ICs are used in this circuit for implementing the amplifyingand logic functions. Use of a dedicated supply is recommended because the integrated circuits will be damaged if the supply voltage is too high, or is of wrong polarity. An external power supply may get connected up the wrong way around, or be inadvertently set to too high a voltage.
Therefore it is a good idea to start by constructing the power supply section and then add the other components of the circuit. If the clock is working, you may turn your attention to the amplifier.LED9 should be off, and should flash when the terminals of capacitor C2 are touched with a wet finger (the classic wet finger test). Preset VR1 may need to be adjusted until LED9 just turns off.The output of gate N2 will be at about half the supply voltage. The output of gate N3 would normally be high. The voltage at the input of gate N3 should vary when preset VR1 is varied. High-efficiency LEDs should preferably be used in this circuit.
The microphone has two terminals,one of which is connected to its body. This terminal has to be connected to circuit ground, and the other to the junction of resistor R2 and capacitor C2. These wires are preferably kept short (one or two centimetres) to avoid noise pickup. With the microphone connected, a loud sound (a clap) should result in LED9 blinking.Adjust preset VR1 so that LED9 stays off on the loudest of background noises but starts glowing when you clap.If the clap-to-start feature is not required, it may be disabled by omitting components D1, D2, R5, C4 and connecting a wire link in place of diode D2.Then IC2 will be alive and kicking all the time.

Agreeable, very close sound imitation
Suitable for sound effects, door-bells etc.

 Parts:

R1,R5 1K 1/4W Resistors
R2 50K 1/2W Trimmer Cermet
R3 8K2 1/4W Resistor
R4 82K 1/4W Resistor
R6 1M 1/4W Resistor
R7,R17,R20,R21 22K 1/4W Resistors
R8,R10,R11,R19 10K 1/4W Resistors
R9 150K 1/4W Resistor
R12 4K7 1/4W Resistor
R13 100K 1/4W Resistor
R14 220R 1/4W Resistor
R15,R22 20K 1/2W Trimmers Cermet
R16 10R 1/4W Resistor
R18 200K 1/2W Trimmer Cermet
C1,C11 47nF 63V Polyester or Ceramic Capacitors
C2,C10,C12 220µF 25V Electrolytic Capacitors
C3 220nF 63V Polyester or Ceramic Capacitor
C4 22nF 63V Polyester or Ceramic Capacitor
C5,C6,C8,C9 100nF 63V Polyester or Ceramic Capacitors
C7,C13,C14 10µF 63V Electrolytic Capacitors
D1,D2,D3,D6__1N4148 75V 150mA Diodes
D4,D5 BAT46 100V 150mA Schottky-barrier Diodes
Q1,Q2 BC547 45V 100mA NPN Transistors
IC1 7555 or TS555CN CMos Timer IC
IC2 4093 Quad 2 input Schmitt NAND Gate IC
IC3 4017 Decade counter with 10 decoded outputs IC
IC4 LM386 Audio power amplifier IC
P1 SPST Pushbutton
SW1 SPST Switch
SPKR 8 Ohm Loudspeaker

Comments:
This circuit generates a two-tone effect very much alike the cuckoo sound. It can be used for door-bells or other purposes thanks to a built-in audio amplifier and loudspeaker
Used as a sound effect generator it can be connected to external amplifiers, tape recorders etc. In this case, the built-in audio amplifier and loudspeaker may be omitted and the output taken from C8 and ground.
There are two options: free running, when SW1 is left open, and one-shot, when SW1 is closed. In this case a two-tone cuckoo sound will be generated each time P1 pushbutton is pressed.
Circuit operation:
IC1 is wired as a squarewave generator and produces both tones of the cuckoo sound. The frequency of the higher one (667Hz) is set by means of Trimmer R2. When IC2D output goes low, a further Trimmer (R22) is added to IC1 timing components via D6, and the lower tone (545Hz) is generated.
To imitate closely the cuckoo sound, the squarewave output of IC1 is converted to a quasi-sinusoidal waveform by R3, R4, C3 and C4, then mixed with the white noise generated by Q1, R6.
Q2 has two purposes: it mixes the two incoming signals and gates the resulting tone, shaping its attack and decay behavior by means of the parts wired around its Emitter.
IC4 is the audio power amplifier driving the speaker and R15 is the volume control.
The various sound and pause timings for the circuit are provided by the clock generator IC2A driving the decade counter IC3. Some output pins of this IC are gated by IC2C, IC2D and related components to drive appropriately the sound generator and the sound gate.
When SW1 is left open the circuit operates in the free-running mode and a cuckoo sound is generated continuously. When SW1 is closed, the circuit generates two tones then stops, because a high state appears at the last output pin (#11) of the decade counter IC: therefore the count is inhibited by means of D1 feeding pin #13.
The circuit is reset by a positive pulse at pin #15 of IC3 when P1 is pressed.
Setup:
Best results will be obtained if the two tones frequencies are set precisely, i.e. 667Hz for the first tone and 545Hz for the second: in musical terms this interval is called a Minor Third. Obviously a digital frequency counter, if available, would be the best tool to setup R2 and R22, but you can use a musical instrument, e.g. a piano or guitar, tuning-up the notes accurately by ear.
Disconnect temporarily R22 from D6 anode
Connect the digital frequency counter to pin 3 of IC1
Adjust R2 in order to read 667Hz on the display
Connect R22 to negative ground and adjust it to read 545Hz on the display
Restore R22 - D6 connection
Tuning by ear:
Disconnect temporarily R22 from D6 anode
Disconnect C8 from Q2 Collector and connect it to R4, C4 and C5 junction
Adjust R2 in order that the tone generated by the loudspeaker is at the same pitch of the reference note generated by your musical instrument. This reference note will be the E written on the stave in the fourth space when using the treble clef
Connect R22 to negative ground and adjust it in order that the tone generated by the loudspeaker is at the same pitch of the reference note generated by your musical instrument. This second reference note will be the C-sharp written on the stave in the third space when using the treble clef
Restore R22 - D6 and C8 to Q2 Collector connections
Notes:
The master clock can be adjusted by means of R18.
The percentage of hiss and sound in the mixing circuit, setting the tone character, can be varied changing R8 and R7 values respectively.
Any kind of dc voltage supply in the 12 - 15V range can be used, but please note that supply voltages below 12V will prevent operation of the white noise generator.
An amusing application of this circuit is to use a photo-resistor in place of P1, then placing the unit near the flashing lamps of your Christmas tree. A sweet cuckoo sound will be heard each time the lamp chosen will illuminate.

1. Introduction 
The basic objective of this project is to include the common features of metro train such as:
LCD display,
Opening and closing of doors with a buzzer,
Driving of dc motors
with the help of interfacing all of them with AT89C51 microcontroller.
A toy car be used in this project which has two DC motors. One can be used for opening and closing the door and other can be used for moving the car forward.


2. The Need 
Delhi, the National Capital with a population of about 12 million is, perhaps, the only city of its size in the world, which depends almost entirely on buses on it sole mode of mass transport.bus services are inadequate and heavily over-crowded.. The result of extreme congestion on the road, ever slowing speeds, increasing accident rate, fuel wastage and environmental pollution. Delhi has now become the fourth most city in the world, with automobiles contributing more than two thirds of the total atmospheric pollution. Pollution related health problems are reaching disconcerting levels.
Immediate steps are, therefore, needed to improve both the quality and availability of mass transport service. This is possible only if a rail-based mass transit system, which is non-polluting, is introduced in the city without further delay.

3. Power Supply System

3.1 Power supply circuit is attached.

The power supply consists of ac voltage transformer, diode rectifier, ripple filter, and voltage regulator. The description of the components is shown below.

3.2 Circuit operation:
In circuit operation, when the voltage generated by the transformer is higher than the capacitor voltage, the current flows through the diode charging the capacitors. At the same time, the load resistor drains current from the capacitors. When the amount of draining matches with the charging current, the voltage is stabilized. A sudden increase in load current will decrease the voltage across the capacitor. It will also increase the time period during which the diodes conduct, hence, the ripple.




4. Project Methodology

4.1 Components:

Component Name Quantity
1. Power Supply Sectionplug with wire 1
Step down transformer (230v/12v a.c) 1
1N4007 diodes 4
LM7809 1
LM7805 1
100 µF 1
ON/OFF switch 1
Red LED 1
1K Resistor 1
2. Microcontroller SectionMicrocontroller IC (AT89C51) with base 1
Crystal Oscillator (11.0592 MHz) 1
Capacitor (30pF) 2
Capacitor (10µF) 1
Resistor (8.2K) 1 LCD Connector 1
3. Buzzer 1
4. LCD(16x2) 1
5. Load Driver (L293D) with base 1
6. A Car (toy-driven by a DC motor) 1 7. General Purpose Card 4
8. Single Core Connecting Wires
9. Reset Switch (Push-on) 1
10. Old and Rough CD drive for making Door System 1
(We are to use only motor and Pulley system for door)

4.2 Softwares used:

1. Keil µVision3.
2. Top-View Simulator

4.3 Equipments used:

1. Soldering iron, solder, flux.
2. Hex Blade



4.4 Procedure of building the Prototype of Metro Train

Step 1: Circuit diagram of the proposed system is designed and finalized.
Step 2: All the components and software platform to be used are selected which
are also mentioned above.
Step 3: All the hardware components are soldered on their respective printed
circuit boards with the help of soldering ion, solder and flux according to
the hardware schematic shown in the Figure
Step 5: Code/program of the proposed system can be developed using assembly
Language or C language with the help of software platform (Keil µvision3).
Step 6: The hex code of the program being created by the software platform is
burnt into the flash code memory of our microcontroller IC 89C51.
Step 7: Testing is done at various levels to finalize the appropriate program for
the most proper working of the system.



4.5 General Working 


When the power is turned on a message (“welcome to metro”) is displayed on LCD. Then a message “Current station is xx” is displayed and door is opened also. A buzzer is also turned on when door opens. After some delay the door is closed and car is started to move forward. A message “current station xx” is displayed also on LCD. After some delay a message “next station is yy” is displayed. After some time the train stops and a message “ current station is yy” is displayed. This process is continued for a number of stations. In the end a message “End of line” is displayed on LCD. This whole process is repeated until we turned off the power supply.

5. Advantages of metro train

Economic Benefits
Metro train benefits to the economy by the way of:
• Time saving for commuters
• Reliable and safe journey
• Reduction in atmospheric pollution
• Reduction in accident
• Reduced fuel consumption
• Reduced vehicle operating costs
• Increase in the average speed of road vehicles
• Improvement in the quality of life
• More attractive city for economic investment and growth

C Code For Project:

Click Here For seeing a Code

Here is a simple temperature controller that turns your personnel computer (PC) off when the temperature of the PC increases beyond the optimal temperature value. Some of the larger integrated circuits become quite hot and if the temperature inside the PC becomes too high, these devices may not be able to dissipate heat fast enough. This, in turn, could lead to failure of devices and eventually of the PC.


Let us assume that the maximum working temperature of your PC is 55°C. So for safe working of your PC, this temperature controller uses a temperature sensor (LM35) and a comparator (CA3140) which disconnect the PC from the power supply whenever the temperature of your PC rises above 55°C. This threshold value is user-adjustable and can be set anywhere between 0°C and 100°C.


The circuit works off 9V DC, which is derived from main power as follows: Mains power supply is rectified by a bridge rectifier comprising diodes D1 through D4,divided by a resistor network comprising R1 and R2, and stabilised by zener diode ZD1. Capacitor C1 filters the ripples.

Using preset VR1 you can set the reference voltage. The reference voltage at non-inverting pin 3 of the comparator is set such that the temperature of the PC is 55°C. When the temperature of the PC is below 55°C, the voltage at the inverting input (pin2) of IC2 is lower than the voltage at the non-inverting input (pin 3). At this stage, the comparator output at pin 6 of IC2 is high. This high output triggers triac 1 (BT136), providing mains power to operate the PC.

When the temperature of the PC increases above 55°C, the inverting input (pin 2) of IC2 also goes above the non-inverting input (reference voltage) at pin 3 and hence the comparator output goes low. This stops triggering of triac 1 (BT136) preventing mains power supply from reaching the PC.Thus this arrangement provides mains voltage to the PC at temperature of up to 55°C and stops when the temperature goes above 55°C.Assemble the circuit on any general-
purpose PCB in the form of a PC expansion card, so you can use it as an add-on card to any PC. Plug it in,switch-on the supply and use your computer with safety temperature device.

you do need a great amount of patience in making this but when you consider the countless hours of pure light -low consumption you'll get, it's all worth it. This tutorial is about converting regular GU4(MR11) halogen bulbs to LED bulbs while maintaining full usability as 12V light bulbs that can be used in indoor task or accent lighting.

You'll need the following stuff to start working:

• one halogen bulb (burnt or new since they are really cheap) with no glass cover on front.
• LED's - as many as you want. You may want to keep this number reasonable since more than 22 LED's will make you work painful.
• online acces to http://led.linear1.org/led.wiz , a great LED array calculator you can use to figure out the resistors you'll need depending on your number of LED's and the supply voltage.
• Super Glue & compound glue. You can use other glue as well but super glue sticks fast and I recomend it.
• solder wire, moderate soldering skills, solder gun
• one small piece of 0.2mm aluminium sheet (this is used in printing industry, I work in this field and there are a lot of aluminium plates around here). Any offset printing shop will be kind enough to give you a used one since they use hundreds each month.
• a paper perforator (office type, 2-hole punch)
• resistors (depending on your needs)
  

a few other common household items along with a good amount of patience.
 Step one - empty the bulb.

Start by taking a small screwdriver and twisting its tip on the white cement you'll see around the bulb's pins. This cement is very fine and will start crumbe as a fine powder as you keep twisting the screwdriver's tip.

Proceed with this until you get enough cement out for the next phase.
Patience is a virtue so take you time and be gentle since the bulbs can easily break if you force you way in with the screwdriver.
Action time. Take a hammer and after you got out out as much white cement you could, put the bulb face-down on a flat surface. Hit the two pins with the hammer, in a easy but ferm manner. The bulb inside should fall on the table leaving the reflector empty.
Some white cement will remain but that's OK, it's not so important and might even be useful later.
 Step two - make your holding disc.

Put the empty reflector aside since it's time to get to another task. It's now time to make the LED support.

You'll need a template so make yourself one. I used graphic software to evenly distribute the 5mm holes on the disc. The disk size is up to you. More led's will require larger disks.

Print your template on paper and cut it out with paper scissors. Place it on the aluminium sheet and light glue it on its surface. This will be useful to cut the disc properly.
 Take the aluminium sheet and cut out the holes using a office perforator. I found out mine cuts exactly 5mm holes in paper so for 5mm LED's it's perfect. Keeping it upside down, place the template along with the aluminium disc glued on it inside it. Cut out the holes after aligning the circles in the cutting hole. This should be easy and fairly quick. For this tutorial, I'll use 22 LEDs and a disk diameter of 4 cm. In this picture you can see another disk I made for 15 LEDs. It's easy and if you practice a little you can make this in minutes.
 The aluminium sheet will serve as a light reflector and a holder for LEDs in the same time so take care not to bend it. After cutting out the holes it''s time to see how the led's should be connected.

Go to  http://led.linear1.org/led.wiz and fill in the fields with your parameters. Here's a screenshot of what the wizard reccomended for my 22 LEDs 12V array. So now I know how to connect them.
 Place the aluminium disc in some holding device (I have one like the one in the photo and it's great). Be creative with this, basically you have to hold the disc by its outer rims. For example, a pipe section with proper diameter will do.
 Insert the Leds into the holes with the legs up and arranged in such a manner that one cathode is next to another anode. This will make soldering easy. Don't forget this or you will have great difficulties soldering them according to the scheme.
Put one tiny drop of Super Glue on each led margin and continue arranging the other ones. WARNING! Take care not to accidentally apply super glue on the LED legs. When you'll have to solder the legs, these will be heated and the glue will give off a little colourless smoke with major effects on your eyes! I know, i've done that and couldn't stopped crying for one hour. I think that's how they make that tear gas after all ...
After all LED's are placed and glued, put compound glue around each LED for a solid result. It is necessary to glue them firmly since the legs will have to be bended and you'll risk some leds to come off otherwise. (that's experience speaking) Now let the glue to harden before proceeding. In my case this meant 24 hours but the result was worth it.
Step three - making connections

Take one nailclipper and cut out the LED legs, keeping in mind that one anode will have to be bent over to the next cathode and so on. Also take care not to confuse the two of them. You can check that with one multimeter set to diodes. As the scheme advises, I'll have to make 5 strings of 4 LEDs each and one string of two. Since I arranged the leds in such a fashion that one cathode is next to another anode, this operation is much easier. After soldering one string, keep the end legs at different lenghts to easily identify the + and the - end.

Take the nailclipper and cut the LED legs and bend them to the next leg. The + goes to a - and so on until you complete a string of four. Then start a new string.

When you're done making all the strings according to the scheme, you should have six + legs longer than the six - ones. It's time to solder the resistors. But first bend the longer legs toward each other and solder them to have all the + legs connected together. This should be done over the other connections keeping some distance to prevent short-circuits. The resistors should be soldered vertically to the - legs.

 When soldering, try to be as quick as possible sice you'll be heating the LED legs close to their base and too much heat will damage them.
 Now solder the resistors legs to each other in order to get a single - that goes to all the strings. Try to keep a low profile so that the whole thing will fit the bulb.
 Now solder the final legs. Use copper wire (thicker) and keep in mind that one (-) has to be shorter.
 The whole thing should now be pretty rigid since so many solderings were made.

But for your peace of mind, use a hot glue gun to fill the gaps so that no wire accidentally touches another. This is optional.
Now take the empty bulb and put the LED disc inside. The space should be enough if you maintained a low profile when soldering.
It fits perfectly. Push the LEDs until the disc touches the inner reflector.
 Hold it still and get the compound glue now.
 Just make sure it's strong enough since it will be the only thing that holds the bulb in one piece. Fill the space around the legs coming out of the bulb with as much glue it will take.
 use a permanent marker to write on the base the + and - legs as well as the voltage it will use.
 Now cut the legs so that it matches the original bulb legs, equal in lenght.
 Job done! It's time for a test. Connect the bulb to a 12V battery (car or anything else providing that voltage). Hold your breath and...
 It's working! The photo actually does not display the amount of light generated as it's blinding if you stare into it directly.

The type of LED's you use is important since a more dispersed light will be better than a concentrated one. You could also file the LEDs prior to making the bulb so as to have a more uniform light. These LED bulbs can also be used in 12V AC spot lamps if you don't mind the 50Hz flicker. But the best results will come out from 12V DC.............

How to make your own led bulbs

View more documents from Masood Alam Shaikh

Spot welders are used in the fabrication of automobiles, PC cases, power supplies, microwave ovens, electrical junction boxes, Faraday cages, and various electronics. A spot welder is used because it produces a highly defined point of contact weld. The materials are welded without excessive heating, so working pieces are handled easily. The weld is also highly controlled and repeatable. In this how-to we cover the basics of a spot welder, and then show you how to build one from a microwave oven transformer.
A spot welder’s electrodes serve at least three functions. They transfer electrical energy to the material while also holding it together; this also controls resistance. The greater the pinch force the less the resistance, which results in decreased resistive heating. A lesser pinch force results in increased resistive heating. The electrodes also conduct heat away from the material, while in the off cycles, helping to cool and temper the weld. A resistive spot weld is commonly referred to as a ‘nugget’. Spot welders are generally confined to ferrous materials which somewhat limits their application range. Most produce a weld with low voltage and high current. The welder in this How-to operates from a secondary of 3vac. The primary is 120vac line voltage that should be treated with respect. The low voltage secondary makes the welder very safe, so the electrical shock hazard from the electrode is virtually non-existent. There is however the risk of burn due to the high temperatures as with any welder.
We also needed some heavy gauge copper wire. We used about four feet of 4AWG wire to build the spot welder in the photo. Other materials included scrap 2×6, 2×2, two copper screw type lugs, two copper welding cable lugs, two MIG welder tips, two 4″ x 3/4″ zinc plated corner braces, drywall screws, and three washers.
Pictured above is a working MOT. The first thing we had to do was remove the secondary coils. Namely the high voltage winding, and the low voltage winding. We used an angle grinder with cut off wheel while being careful not to cut the primary winding.
We cut the secondary flush with the MOT laminate core. Both sides of the MOT should be cut. Inspect the MOT for signs that the laminate has been welded. We have found that welded MOTs can handle a little more abuse than their sealed only counter parts. If possible try to keep the core insulation intact, where the secondary will be wound. Though it is not a show stopper if the insulation becomes damaged. The insulation makes it a little easier to wrap the heavy gauge secondary.

 After removal of the secondary we had something that resembles the above photo. If the magnetic shunt material falls out be sure to replace it as it was before. The shunt keeps the core from transferring too much power to the secondary. A magnetic ballast if you will. The shunt acts to control the saturation of the core. A brute force project like this relies on such a shunt for proper operation.
Rewinding a MOT with 4AWG is no walk in the park. If you’ve damaged the core insulators, we suggest wrapping a layer of electrical tape in their place. This will help to avoid damaging the insulation on the wire as it is pulled through the core.  Our experience is that 3-4 windings is plenty. After all, this spot welder relies on high current and marginal resistance. Not high voltage.

We were careful to ensure that the secondary coil was wrapped in a helical manner to complete the secondary.
We mounted the MOT and 2×2 to the 2×6 base. This particular build used 12″ 2×6 with two 7″ 2×2. These dimensions may or may not work depending on the physical size of your MOT. The only critical part here is keeping the wire length as short as possible.
After the lower jaw was mounted, we also attached the corner braces. It was found that a spare piece of 2×2 as a shim worked well to align the upper and lower jaw. After the upper jaw was aligned we attached it to the corner braces with screws. This formed the hinged portion of the jaw.
The picture above shows the MIG welder tip and the screw type copper lug. This is an improvement from an earlier model we had built. Initially, we used copper tubing with a hole and a piece of 6AWG grounding wire serving as the welding electrode. The grounding wire was held in place by a screw that threaded inside the copper tube perpendicular to the electrode. It was very crude, but it worked. This new method is much more practical.
Here are the two electrodes ready to be fixed to the lower and upper jaws. We double checked the MIG electrodes to make sure they were tight. A loose connection will take heat away from the weld nugget.
Evenly aligning the welding electrodes, we were careful to keep the upper jaw in the natural position where it was mounted. This maintained a flat contact area for the welding electrodes. After we were sure that the electrodes had been properly aligned, the jaws were marked. We then drilled a small hole. Since we mounted with the grain of the 2×2 the holes helped to protect from splitting the 2×2.
With the electrodes mounted, we cut the wire to proper length. We never cut the exact amount we need. We always cut more than we need. This rule of thumb should apply to all electrical wiring. After all it is much easier to cut off excess than wrap a new secondary.
 We bent the wires in to the approximate positions in which they were to be assembled and stripped the wire in preparation for the crimp type welding lugs. It is a good idea to strip more than is needed here as well. Simply cut off excess after sizing up the lugs depth. Never crimp insulation with the lug. This will create a potential problem area due to the loss of conduction.

 Using a good non insulation crimp tool to secure the wire. We inspected the crimp and gave it the tug test. Simply tug on the wire if it is loose it will pull out. It if doesn’t pull out then an adequate crimp suitable for high current has been made.
The crimped wires were attached to the welding electrodes with screws. We were careful not to over tighten the screws. If a drywall screw had stripped out of the wood, we would have had to use a larger wood screw in its place. After both welding electrodes were fixed to the jaws, we aligned the electrodes. Using pliers we bent the electrodes so that they contacted each other evenly. The electrodes should be fairly close already since they were aligned before drilling.
We opened the jaws and wired the primary to an electrical cord and then tested the secondary. If the breaker trips, check for the following:

1. The secondary is  shorted (the jaws are closed)
2. The magnetic shunts are missing or not properly reinstalled
3. Faulty line wiring to primary or shorted primary
4. Too much load on the circuit of test or undersized breaker

We observed proper electrical wiring practices. It is also stressed that this is a welder and it should have a dedicated circuit as any other welder would have.
With the power physically disconnected we verified the welding electrode alignment with the material we intended to work on. Before connecting the power and performing an initial weld, we observed a few safety guidelines. This is a welder and will produce very high temperatures. Keep fingers away from the welding electrodes. Allow the material to cool prior to handling. Always wear eye protection. You may be interested in reading about spot welder parameters. There’s also the problem of combustible materials…

 This Compaq used very thin aluminum to support the screen and connect the hinges. The metal broke and destroyed most of the lower plastic. We were able to make new supports from 22AWG stainless steel sheet metal. All the welds were made using the spot welder with a special power controller.