Automatic Emergency Light

Nowadays, an automatic emergency light is a very important tool in our daily lives. An automatic emergency light is a battery-backed lighting device that turns on automatically when we experience a power outage. Emergency lights are standard in new commercial and high occupancy residential buildings, such as college dormitories. Most building codes require that they be installed in older buildings as well.

The circuit I am going to share is a fully automated circuit which turns off charging automatically when the battery is fully charged so you can keep it connected to your wall socket all day long without worrying about over charging issues.

Components Required:

1. NE555 IC
2. LM317 IC
3. Ferrite Transformer with 22 primary and 34 secondary turns
4. Center Taped Step down transformer 500mA 9V-0-9V
5. Tubelight 20W
6. 6V 4Ah Battery
7. SL100 Transistor (with heat sink)
8. 2N3055/MJE3055 Transistor (with heat sink)
9. 2x BC547 Transistor
10. 3x 1N4007 Diode
11. Zener diode 6.8V (0.5W)
12. 2x 0.01 uF Capacitor
13. 0.1 uF Capacitor
14. 6.8 uF Capacitor (25V)
15. Pot 1 Kohm Variable Resistor
16. 2x 1 Kohm Resistor
17. 2x 4.7 Kohm Resistor
18. 10 Kohm Resistor
19. 100 ohm Resistor
20. 150 ohm Resistor

Components Required:

1. NE555 IC
2. LM317 IC
3. Ferrite Transformer with 22 primary and 34 secondary turns
4. Center Taped Step down transformer 500mA 9V-0-9V
5. Tubelight 20W
6. 6V 4Ah Battery
7. SL100 Transistor (with heat sink)
8. 2N3055/MJE3055 Transistor (with heat sink)
9. 2x BC547 Transistor
10. 3x 1N4007 Diode
11. Zener diode 6.8V (0.5W)
12. 2x 0.01 uF Capacitor
13. 0.1 uF Capacitor
14. 6.8 uF Capacitor (25V)
15. Pot 1 Kohm Variable Resistor
16. 2x 1 Kohm Resistor
17. 2x 4.7 Kohm Resistor
18. 10 Kohm Resistor
19. 100 ohm Resistor
20. 150 ohm Resistor

Circuit Diagram:

The circuit can be divided into inverter and charger sections. The inverter section is built around timer NE555, while the charger section is built around 3-terminal adjustable regulator LM317. In the inverter section, NE555 is wired as an astable multivibrator that produces a 15kHz squarewave. Output pin 3 of IC 555 is connected to the Darlington pair formed by transistors SL100 (T1) and 2N3055 (T2) via resistor R4.

The Darlington pair drives ferrite transformer X1 to light up the tubelight. For fabricating inverter transformer X1, use two EE ferrite cores (of 25×13×8mm size each) along with plastic former. Wind 10 turns of 22 SWG on primary and 500 turns of 34 SWG wire on secondary using some insulation between the primary and secondary. To connect the tube-light to ferrite transformer X1, first short both terminals of each side of the tube-light and then connect to the secondary of X1. (You can also use a Darlington pair of transistors BC547 and 2N6292 for a 6W tube-light with the same transformer.)

Working:

When mains power is available, reset pin 4 of IC 555 is grounded via transistor T4. Thus, IC1 (NE555) does not produce square-wave and emergency light turns off in the presence of mains supply. When mains fails, transistor T4 does not conduct and reset pin 4 gets positive supply though resistor R3. IC1 starts producing square wave and tube-light turns on via ferrite transformer X1. In the charger section, input AC mains is stepped down by transformer X2 to deliver 9V-0-9V AC at 500mA. Diodes D1 and D2 rectify the output of the transformer. Capacitors C3 and C4 act as filters to eliminate ripples.

The unregulated DC voltage is fed to IC LM317 (IC2). By adjusting preset VR1, the output voltage can be adjusted to deliver the charging voltage. When the battery gets charged above 6.8V, zener diode ZD1 conducts and regulator IC2 stops delivering the charging voltage. Assemble the circuit on a general-purpose PCB and enclose in a cabinet with enough space for the battery and switches. Connect a 230V AC power plug to feed charging voltage to the battery and make a 20W tube outlet in the cabinet to switch on the tube-light.

Electronic Dice

You can make yourself an Electronic Dice that works just like a dice in a game giving random number whenever you press the button. It can be used in games and for children who dont know how to roll the dice or also for handicapped persons.

It is a simple and classic project for those getting interested in electronics. A timer, counter and a few LEDs makes a circuit that can also add a new twist to some old boring board games.

It is a tested and 100% working circuit.

Components Required:

1. NE555 IC
2. 4017B IC
3. 6x 1N4148 Diode
4. 7x Red LEDs
5. 4x BC109 Transistor
6. 7x 1 Kohm Resistor
7. 5x 10 Kohm Resistor
8. 2x 2.2 Kohm Resistor
9. 100 Kohm Resistor
10. 22 uF Capacitor
11. 0.01 uF Capacitor
12. Push Switch Button

Circuit Diagram:

Connect all the arrows on the transistors to the positive supply rail.

The LEDs Should Be Alligned As Following Image

Working:

The 555 timer IC is connected for Astable Operation, the clock pulses are fed to the 4017 IC via the 10K resistor. The 4017 is a 10 stage counter, output 6 (pin 5) is connected to RESET (pin 15), thus giving us a 6 stage counter , outputs 0 to 5.

6 of the LEDs are connected as 3 pairs, thus requiring 4 different signals, these signals come from the 4 transistors, which in turn are connected to the nescessary outputs of the 4017. Where a transistor is operated from more than one output, diodes are used to avoid a short circuit situation between outputs.

Pin 13 of the 4017 (INHIBIT) is connected to +ve via a 100K resistor to stop the counter from advancing, however pressing the ROLL button will connect pin 13 to -ve and allow the counter to advance, hence, throwing the dice.

LED Flasher Circuit

Today we are here with a very simple and cheap project for new comers to electronics field and for all hobbyist out there. This circuit is a LED flasher circuit that drives 48 white LEDs at once with a 12V battery and a 555 timer IC.

Note: The circuit is tested and 100% in working condition. Credit goes to Wajeeh Uddin of Hamdard University for providing us with images and testing the circuit.

LED Flasher Circuit

Components Required:

1.  12V Battery
2. On/Off Switch
3. 555 Timer IC
4. 10 uF or upto 100uF Capacitor
5. 33 Kohm resistance
6. 48 x White LEDs
7. 16 x 82 ohm Resistance

Circuit Diagram:

Working:

The 555 is capable of sinking and sourcing up to 200mA, but it gets very hot when doing this on a 12v supply. The following circuit shows the maximum number of white LEDs that can be realistically driven from a 555 and we have limited the total current to about 130mA as each LED is designed to pass about 17mA to 22mA maximum. A white LED drops a characteristic 3.2v to 3.6v and this means only 3 LEDs can be placed in series.

So if you are new in the field of electronics and want to learn making circuits or learning about the operation of 555 timer IC then this project is the most ideal and simplest project for you. You can even place this circuit in a suitable enclosure and put it up somewhere as a piece of decoration for house or even connect it into your car battery and place the LEDs inline if you like.

Digital Code Lock – DIY Project

A Digital Code Lock project is introduced in this article which is a really simple and low cost DIY project. There are many other digital code lock circuits available some use a certain set of switches to be pressed in a certain time and some use microprocessor or different ICs.

This circuit is a really simple circuit that uses NE555 timer IC and contains 10 switches to control the lock. Only 6 out of 10 switches are used in a particular sequence to open the lock.

Note: The circuit is tested by myself and in 100% working condition.

Components Required:

1. Center taped step down transformer 6V-0-6V
2. 4x 1N4001 Diode
3. 10x Push Button
4. NE555 IC
5. 6V Relay (100 ohm)
6. 1 uF Capacitor (16V)
7. 0.01 uF Capacitor
8. 5 uF Capacitor (16V)
9. 1000 uF Capacitor (16V)
10. LED red
11. 1 Mohm Resistor
12. 2x 10 Kohm Resistor
13. 1 Kohm Resistor
14. 820 ohm Resistor
15. Solenoid

Circuit Diagram:

Working:

Here the keying-in code is rather unique. Six switches are to be pressed to open the lock, but only two switches at a time. Thus a total of three sets of switches have to be pressed in a particular sequence. (Of these three sets, one set is repeated.)

An essential property of this electronic code lock is that it works in monostable mode, i.e. once triggered, the output becomes high and remains so for a period of time, governed by the timing components, before returing to the quiescent low state. In this circuit, timer IC 555 with 8 pins is used. The IC is inexpensive and easily available. Its pin 2 is the triggering input pin which, when held below 1/3 of the sup-ply voltage, drives the output to high state. The threshold pin 6, when held higher than 2/3 of the supply voltage, drives the output to low state. By applying a low-going pulse to the reset pin 4, the output at pin 3 can be brought to the quiescent low level. Thus the reset pin 4 should be held high for normal operation of the IC.

Three sets of switches SA-SC, S1-S8 and S3-S4 are pressed, in that order, to open the lock. On pressing the switches SA and SC simultaneously, capacitor C3 charges through the potential divider comprising resistors R3 and R4, and on releasing these two switches, capacitor C3 starts discharging through resistor R4. Capacitor C3 and resistor R4 are so selected that it takes about five seconds to fully discharge C3.

Depressing switches S1 and S8 in unison, within five seconds of releasing the switches SA and SC, pulls pin 2 to ground and IC 555 is triggered. The capacitor C1 starts charging through resistor R1. As a result, the output (pin 3) goes high for five seconds (i.e. the charging time T of the capacitor C1 to the threshold voltage, which is calculated by the relation T=1.1 R1 x C1 seconds).

Within these five seconds, switches SA and SC are to be pressed momentarily once again, followed by the depression of last code-switch pair S3-S4.

These switches connect the relay to out-put pin 3 and the relay is energised. The contacts of the relay close and the solenoid pulls in the latch (forming part of a lock) and the lock opens. The remaining switches are connected between reset pin 4 and ground. If any one of these switches is pressed, the IC is re-set and the output goes to its quiescent low state. Possibilities of pressing these reset switches are more when a code breaker tries to open the lock.
LED D5 indicates the presence of power supply while resistor R5 is a cur-rent limiting resistor.

Summary: Press switches SA SC in unison at first ,then press switches S1 S8 in unison just after releasing SA SC within 5 seconds,after releasing S1 S8 again press SA SC in unison within 5 seconds and just after it press S3 S4 in unison and your relay will be energised.

– You can enlose this circuit in a suitable enclosure and put digit numbers on all the buttons from 0-9. And remember the combination so only you can open the lock through the code. You may also add a green LED at the end just before the relay in series with a suitable value resistor so you can check the status of the relay if its on or off just as i have added in the breadboard circuit.

2 easy DIY projects – make a orange candle & cassette tape wallet !

Lets start with how to make a candle with orange.

Thing needed :

• an orange
• any type of oil like vegetable or olive oil

Remove /eat the middle portion of the orange but be careful to leave the middle stem like portion intact. Easy way to remove the middle portion can be done by a sharp knife and digging out the middle starting with the closest edge outside the orange .Fill the empty/cavity with oil just below the center stem like wick. Light the center stem like wick . This orange can be burned for most of the day.

Now head towards the making of cassette tape wallet

Cassette tapes may be outdated and a bit obsolete, but you can still enjoy your favorites or some kitschy titles with this easy cassette tape wallet. Whip this baby out at the checkout and reap the conversational rewards.

Thing needed

• An old cassette tape
• A scrap of fabric (At least as wide as your cassette and twice as tall.)
• Scissors
• chalk
• Hot glue gun
• Sewing needle and thread .

First, you’ll need to take apart the cassette tape. Depending on how old it is, this can prove to be a difficult task. My tape is a little old, so I needed to fetch a screwdriver to remove five screws that held the tape together.

More recent tapes will require you to pop a few plastic prongs that hold the tape together. To do this, slip a dull butter knife or flathead screwdriver in the center crack of the cassette. Pry it up until you’ve popped apart the glue holding it together. Be careful that you don’t crack the tape in the process… lots of tapes die this way.

Pick a felt or fabric lining that will complement the color of your tape or zipper. You won’t need much fabric at all for this, so dive into that scrap pile for some old favorites.Lay the sides of the cassette top to bottom and use your chalk to trace around them on the fabric.Cut it out and put your fabric aside for now.

We are going to attach the top of the zipper first, where the head of the zipper is. Don’t worry about trimming the extra zipper length right now.

Use your hot glue gun to lay down a line of glue inside one edge of a cassette half.

Very carefully press the side of the zipper into the glue, as shown. You need to be careful because if that glue gets into your zipper teeth, you’ll be spending some time picking it out.

Gluing the top of the zipper means you’ll have to negotiate the corner. To do this, make a little fold in the edge of the zipper, as shown.

Lay a strip of glue all along the top of the cassette, then carefully press on the zipper. After this is dry, dab a dot of glue under that corner flap and hold it down until the glue cools.

For the last side, you’ll need to make that folded corner again and glue just as you did in the last step.

Lay down the glue right to the end, and press on the zipper even if it is too long and hangs over the edge of the tape.

Give the zipper a snip right at the bottom edge of the cassette. Now you’ll need to sew up the end of the zipper to keep the zipper head from slipping right off.

In this step, you need to be careful not to glue your cassette so that the halves of the tape are uneven. To do this, we’ll zip it up as we glue.

Unzip the zipper. Lay a strip of hot glue along the edge of the next cassette half that will be at the bottom of the zipper, as shown. Press the edge of the zipper into the glue, being very careful not to let the glue bubble over onto the teeth of the zipper.

When the glue is dry, zip up that part of the zipper. Glue along the top of the cassette, folding the corner over just as you learned to do in the last step. Again, watch that the glue doesn’t get on the zipper teeth! When the glue is dry, zip up the top zipper.

Finally, put a strip of glue on the last side and press on the remaining length of zipper, folding the corner as before. Add dabs of glue on those folded corners and press until the glue has cooled.

Trace a line of hot glue along the inside of the zipper. Lay your cut fabric to match the hot glue.

If you have extra fabric around the glue, clip it after the glue dries. You need to clip the extra fabric to prevent it from getting stuck in the zipper.

Repeat with the other side, carefully folding up the fabric to stick on the other side. Clip extra fabric as needed.

The side of the wallet with the tail of the zipper will have a wide opening when it’s unzipped. When it’s closed, it will be a hole that your change can slip out of. Nobody wants that.

Use a simple overcast stitch to close up this edge. Now your cassette tape wallet should becomplete.

No matter what, be sure you keep the hot glue off of the zipper teeth. Even residual glue will give you trouble when you’re zipping. Try finding cassettes of your friend’s favorite bands. This is a great gift for someone on your list.

Mini UPS System For Router/Mobile Charger – DIY Project

If you are tired of load shedding problems and want to have a mini UPS system which can power up your home router for internet purposes and also charge your mobile phone then here is a circuit for you to do it yourself and get along with the load shedding problems.

The circuit provides an un-interrupted power supply (UPS) to operate 12V,9V and 5V DC-powered instruments at up to 1A current. Its not a pretty difficult circuit to make and the only expensive component in the whole circuit is the 12V battery.

Components Required:

1. 12V (4.5 Ah) Battery
2. 12-0-12 V , 1A Center Taped Transformer
3. 4x 1N4007 Diode
4. Zener Diode 10.5V (0.5W)
5. Zener Diode 12V (1W)
6. 3x LEDs (Red,White,White)
7. 68 ohm Resistance (0.5W)
8. 2x 1 Kohm Resistance
9. 47 ohm Resistance (1W)
10. 2x 390 ohm Resistance
11. Pot 10 Kohm Variable Resistance
12. Pot 22 Kohm Variable Resistance
13. 470 uF Capacitor (25V)
14. Transistor BC548
15. Transistor TIP 127
16. IC 7809
17. IC 7805
18. On/Off Switch

Circuit Diagram:

Working:

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.

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 falls 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 voltages 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.

Precautions:

The circuit should be assembled on a general-purpose PCB or Vero Board.There must be adequate space between the components to avoid overlapping. Heat sinks for transistor T2 and regulator ICs (7809 and 7805) to dissipate heat must be 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 supply and connect a fully-charged battery to the terminals and see that LED1 is on. After making all the adjustments connect the circuit to the battery and transformer.

You can now connect your internet router to the 12v supply and use the 5v output for charging your mobile phone.

Mobile Car Stereo Player – DIY Project

Using a mobile phone while driving is dangerous. It is also against the law. However, you can use your mobile phone as a powerful music player with the help of a stereo power amplifier. So here we would like to share a (do it yourself) “Mobile Car Stereo Player” circuit that you can make by yourself if you have enough knowledge about electronics and building circuits.

Most mobile phones have a music player that offers a number of features including preset/manual sound equalisers. They have standard 3.5mm stereo sockets that allow music to be played through standard stereo headphones/sound amplifiers. Nokia 2700 classic is an example.

A car audio amplifier with 3.5mm socket can be designed and simply connected to the mobile phone output via a shielded cable with suitable connectors/jacks (readymade 3.5mm male-to-male connector cable is a good alternative).

Circuit Design:

Working:

IC TDA1554Q contains four 11W identical amplifiers with differential input stages (two inverting and two non-inverting) and can be used for single-ended or bridge applications. The gain of each amplifier is fixed at 20 dB. Here it is configured as two 22W stereo bridge amplifiers.

The amplifier is powered from the 12V car battery through RCA socket J2. Diode D1 protects against wrong-polarity connection. LED1 indicates the power status.

Connect stereo sound signal from the 3.5mm headset socket of the mobile phone to audio input socket J1. When you play the music from your mobile, IC1 amplifies the input. The output of IC1 is fed to speakers LS1 and LS2 fitted at a suitable place in your car. Electrolytic capacitor C5 connected between pin 4 of IC1 and GND improves the supply-voltage ripple rejection. Components R2 and C4 connected at mute/standby pin (pin 14) of IC1 eliminate the switch on/off plop.

The circuit is quite compact. A good-quality heat-sink assembly is crucial for IC1. Fig. 2 shows the stereo socket and stereo jack.

Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Small dimensions of the power amplifier make it suitable for being enclosed in a plastic (ABS) case with vent holes. Signal input socket, speaker output terminals, on/off switch, indicator, fuse holder and power supply socket are best located on the front panel of the enclosure as shown in Fig. 3.