Power supply from your CPU

How'd you like a high-quality regulated 5V and 12V bench supply for less than Rs 30?
It’s pretty easy, and you won't even need a soldering iron.

Inside every PC is good quality switching power supply. The exact details depends on the PC, but you can expect to find regulated 5V and 12V often at 200W or more of power. Modern PCs rarely consume that much power, so there is plenty of spare juice for your projects. The problem is how to get to it.

In this article I'll show you a quick and easy way to gain access to your PCs power supply. Of course, you need to be careful not to exceed the maximum current capacity of the supply--don't run your 100W stereo amp from the PC supply! For many projects, however, you can use the +5 and +12 supplies with no ill effects. This is pretty good for any digital device that needs highly regulated +5v and +12v. Logic uP microcontrollers (using parallel port to send RF signals and CMOS cams work great on this rigged up power supply.

Construction is very simple. Just remove an unused drive plate. These plastic plates cover the holes where you would install a floppy disk or a disk drive. I used a 5.25 inch cover, but if you only have a 3.5 inch cover open, that should work just as well. Be sure there isn't a disk drive behind the plate -- sometimes there is a hard drive hiding behind one of these plates.

Using a center punch/compass/long nail, mark 4 holes in the plate equally spaced Then drill out the holes to fit 4 binding posts; if u don’t have drilling equipment, use a cheap 20-30 w soldering iron to melt the hole thru and file the rough edges. . Mount the binding posts on the drive plate. You should use two black posts in the center 2 holes. It is nice if you can find a red post for the 5V supply and another color post (I used yellow) for the 12V supply.

The next piece of hardware you need is a Y splitter .This is a wiring harness that plugs in to the connectors that the power supply provides and ends in two similar connectors. You usually use these when you have run out of connectors and you want to add something else to your PC.

Locate one of the female connectors on the Y splitter and cut it off close to the connector body. Strip the wires back about a half inch. If you are meticulous, you could crimp on some spade lugs or ring terminals to the wires. However, you can also just work with the bare wire. The splitter has two black wires (ground), a red wire (5V) and a yellow wire (12V). Connect these to the appropriate binding posts.

Feed the wiring harness back into the PCs body and reinstall the drive plate. If you can locate a free connector from the power supply, just plug the mating connector on the harness into it and you are set. If you don't have a free connector, don't worry. Find the closest disk drive and gently remove the power connector from it. Replace it with the connector from the wiring harness. Then plug the newly freed connector into the harness. Now the drive has power, and so do the binding posts.

Here's what it looks like ready to install:





Before your button up the PC, take a look at the power supply's label and see if you can get idea of how many amps the supply can handle. Of course, the PC is taking some of this power, but the trend has been towards lower-powered cards and drives, making most PC supplies quite large for their typical load. Turn on your PC and measure the voltage at the binding posts.

There are many things you could do spruce this project up. For example, you could mount a cheap digital panel meter in another drive plate to monitor the voltage or current. You could also mount an inline fuse holder in the wires leading to the binding posts. In particular, if you short something accidentally, you run the risk of damaging your PC. Every time I've done this, the power supply just shut down until I cycled the input power (with the short removed) and there was no other harm done.

Whatever you do, you'll get a useful addition to your bench and one other benefit. Everyone who sees those posts sticking out of your PC will want to know what they are for!

By the way, another good way to get a 5V supply is to cut the end off of a USB cable, find the red and black wires (make sure with a voltmeter) and connect them to some sort of connector or binding posts. This has the advantage of being highly portable. Powered USB hubs can provide 500mA at 5V and many are current limited!

Imp; Keep these in mind- Take care that u do not short the supply, especially if you haven rigged in a fuse. & do NOT load it more than 3-4 Amps. That’s about it. I rigged them in a hurry cause I had to power 4 CMOS X10 cams, and the power adapters were rated 110v/60htz(for USA)Hence, I am using these to power them.. They work like a charm :)

The next project I am doing is a full version of power supply (+5v, +3.3v, +12 v,-5v,-12v) using a scrapped CPU SMPS power supply which works independently and after finishing that I am converting a regular surveillance cam infrared spy cam.
Have fun :)
My upcoming projects (already in progress) pic below-




Any problems, contact me at csingh@gmail.com.

Solar Charged LED Utility Light

This is almost the same as the one posted earlier,but with a simpler circuitry.

Introduction
Tired of always spending money on flashlight batteries only to have them fail just when you need them? Try this simple circuit out. It would make an excellent science fair project. The white LEDs are quite bright, they provide enough light to illuminate a small room at night. The LEDs produce a nicely focused beam. You can read by the light of this device. The red, orange, yellow and green LEDs broaden the lamp's color spectrum to produce a slighly warmer color temperature.
The box also doubles as a 12V power source and can run other small loads such as a transistor radio. This project was built with the Simpler is Better approach, the materials are common and many substitutions are possible.

Specifications
Operating Voltage: 11-12.8V DC
Solar Charging Current: 60ma approx.
LED Lamp Operating Current: 60ma approx.

Theory
The solar panel puts out about 60ma of current, this is enough to float-charge the 12V gell cell without overcharging. With this limited amount of current, a charge controller is not required. Other batteries may be used such as smaller lead acid batteries or NiCd cells (use 10 in series), but overcharging and leaking battery goo may result if you exceed the battery charge ratings. A smaller and lighter 3.5 Amp Hour 12V lead acid battery has been successfully used in a different version of this circuit, the price is about the same as the more common 7 Amp Hour battery.
There are 3 series strings of LEDs in this circuit, the resistors limit the current through the LEDs and prevent them from burning up. The white LEDs have a higher voltage drop and only 3 can be used in series with a 12V (11-13V) source. The red/orange/yellow LEDs have a lower voltage drop per diode, so 4 can be wired in series. The colored LEDs are optional, they are used to increase the red side of the color spectrum. White LEDs can be expensive. If you are on a budget, try building the light with just one string of three white LEDs and a single resistor.

It is possible to adapt this basic circuit to work with a lower battery voltage, such as 6V. At 6V, the lamp circuit would need to be changed to one white LED and one resistor per string, and a set of red/yellow LEDs and one resistor per string. The resistor values would need to be changed to maintain a 20-25ma current through each LED. A lower voltage solar panel could be used to charge the 6V battery, a 7.2V (open circuit voltage) panel would be a good fit.



Construction
Most of the effort went into building the box, any shape will do, but this unit was built so that the battery just fit inside and the solar panel is mounted at approximately 45 degrees from horizontal. I used particle board and wood screws to hold the box together, other materials will be more rain proof. White gloss paint was applied to give the particle board some protection from rain and keep the box cool in the sun.
The LED mounting system is somewhat fragile but allows the light to be rotated up and down. The cylinder is made from an unthreaded spacer with a 4-40 screw hole tapped in the middle for connecting the LED circuit board. The C mount is just a piece of flat aluminum that I bent in a vise, hammered into shape, trimmed with a pair of tin snips, and filed smooth. The LED circuit board is mounted behind a white plastic water bottle cap, the cap shields the light that escapes from the sides of the white LEDs.

The LED circuit board was custom built with press-n-peel film but can easily be built with a piece of perforated board or prototype PCB material. The resistors are mounted on the circuit board, along with the LEDs. Don't overheat the LED wires when soldering, white LEDs are expensive and LEDs in general can be destroyed by over heating. When soldering, clip a heat sink to the LED leads.

All wiring was done with stranded #22 gauge wire and wire nuts. Note that the specified solar panel comes with its own built in diode, that will work fine, but a 1N5818 schottky diode in parallel with the existing diode will give slightly more charging current due to a lower voltage drop.

Use
Turn off the LED switch and point the solar panel at the sun in the morning, adjust the panel towards the sun a few times a day, or simply point the panel in the direction of the sun at noon. The battery will charge. Turn the light on at night, it should run for many hours. The box will maintain a charge if it is left in a sunny spot indoors. One full day of charging should be enough for several nights of light.
The pin jacks can be used to occasionally check the battery voltage, under sunlight the voltage rises up to about 12.8V and at night, it should not be allowed to go below 11V or the battery life will be shortened. A new, fully charged battery will run the light for around 100 hours, so if you put the box in the sun during the day, total discharge should not be a big problem.

Experimenters will want to measure the current in and out of the battery, this can be done by inserting an ammeter in series with the fuse and the battery. Other 12V loads can be powered by this system, just plug them into the pin jacks or better, add a polarized output connector.

I have been using this device for four years. It sits in a sunny window and continues to provide a reliable source of light at night.

Parts
1x 12V 7AH sealed lead acid battery, Panasonic LC-R127R2P or Yuasa NP7-12, from DigiKey
1x GM-684 12V 60ma solar panel, p/n 08SLC09 from Elecronix Express
1x red LED, T1-3/4 size
1x orange LED, T1-3/4 size
1x yellow LED, T1-3/4 size
1x green LED, T1-3/4 size
6x white LEDs, T1-3/4 size from Jameco
2x 120 ohm 1/4 W resistors
1x 220 ohm 1/4 W resistor
1x 1/2 Amp 28VDC fuse
1x fuse holder
2x crimp on battery clips
3x wire nuts
1x 1N5818 diode
1x spst toggle switch
2x pin jacks
1x box large enough to fit the battery and solar panel.
misc hardware

Solar Powered Reading Lamp

The goal of this project was to produce a self contained reading lamp that could be used by students in developing countries for reading at night. The circuit can be used for a wide variety of lighting applications.
The reading lamp consists of a small solar panel, a standard UPS style lead acid battery, and an LED circuit board. The circuit board contains a low power solar charge controller (regulator), a set of 8 white LEDs, a switch, an LED current regulator, and a low voltage disconnect circuit. The circuitry will insure a long battery life by preventing over charging and excessive discharging. The circuit was designed to work with lead acid batteries, it should also work with a string of 10 NiCd cells. Both the charge controller and LED regulator circuits can be used independently for other applications.

An inexpensive 12V 7AH lead acid gell-cell battery that is typically found in a computer UPS is also a good fit for this circuit. Be sure to use a new battery.

Specifications
Solar charging current: 150 ma - 1 Amp
Voltage drop through charge controller: 0.5V typical
Nominal battery voltage: 12 Volts
Battery rating: 3-7 amp hours
LED lamp current: 100ma regulated, 25ma per LED pair (1.2W nominal)
LED regulation range: constant light level from 11V to >15V
Low voltage disconnect: gradual current drop from 10.8V to 9.8V
Night time battery current drain with LED off: almost zero
Light duration: approximately 70 hours with a 7AH battery
Charge time: approximately 40 hours max, several hours typical



Theory
Charge Controller: The charge controller section consists of an LM2941CT low dropout voltage regulator and a 1N5817 schottky diode. The regulator determines the battery full voltage, this set-point is adjusted by the 5K 20 turn trimmer potentiometer. The 1N5817 schottky diode prevents the battery from discharging through the voltage regulator during the night. It also protects the circuitry against reverse battery connection. The V727 part is a transzorb, it absorbs lightning induced voltage spikes above 27V. The fuse prevents short circuits from burning up the battery wiring.
LED Circuitry: The 8 white LEDs are connected in series with an LM317L IC that is wired as a constant current regulator. The 13 ohm resistor sets the regulated current to 100ma. This current is split evenly through the four pairs of LEDs. The 33 ohm resistors help to keep the current through the four LED pairs balanced evenly. The 2N3904 transistor, 1N5239 zener diode, and 470 ohm resistor form the Low Voltage Disconnect (LVD) circuit. Current through the LED starts to drop when the battery voltage drops below 10.8V, the circuit shuts off almost all of the current when the battery drops below 10V. The 1N5817 schottky diode blocks current flow in the event of a reverse battery connection.

Construction
The lamp consists of a small wood battery box and a vertical board for holding the LED assembly and solar panel. A small carrying handle protrudes from the top of the vertical board. The LED assembly consists of a small printed circuit board and the various parts. It is sandwiched between a piece of hard-board and a piece of clear plexiglass to protect the circuitry from physical damage and short-circuiting. The battery used for this device is a standard 12V-7 Amp-hour gell cell UPS battery. The solar panel is home-made, two or three parallel-wired 12V 60ma solar panels would be a good substitute.
Alignment
[]Connect the board's BAT - terminal to the battery - terminal.
[]Connect the board's BAT + terminal to the battery + terminal.
[]Connect the board's PV - terminal to the solar panel - terminal.
[]Connect the board's PV + terminal to the solar panel + terminal.

[]Point the solar panel toward the sun.
[]Measure the connected solar panel's voltage with the meter.
[]Measure the battery voltage with the meter.
The solar panel must be at a higher voltage than the battery for the
circuit to charge the battery.

[]Turn the potentiometer, VR1 25 turns clockwise.
[]Monitor the battery voltage, as the battery charges, the voltage should
rise above 13V.
[]When the battery voltage has reached 13.8V or the desired full point,
turn VR1 counter-clockwise until the battery voltage stabilizes.
[]Let the battery charge for several minutes at the full setting, then
re-adjust VR1 for the final desired full voltage setting.

Use
Daytime: Place the solar panel in a location that gets at least a
few hours of direct sunlight each day. Turn the LED switch off.
If the battery is extremely discharged, it may take several days in
the sun to fully recharge.

Night: Use the lamp as you would use any other reading lamp.
If the lamp starts to dim, the battery is almost completely empty,
shut the light off. If you forget to shut off the lamp, the LVD circuit
will shut the lamp off when the battery is nearly empty.
If the lamp is recharged daily, the battery should
rarely reach the Low Voltage Disconnect (LVD) point.

Introduction

I have always succumbed to the desire to break things just to find out how they work. I know..I know..its a sick way to enlighten yourself...but I cant help it.

Been doing this for aslong as I can remember... and along the way learned that most things that seem as immensely complicated are actually a cakewalk once you know how it works.

I am trying to compile some projects which I have already made..and hope that one of you might just want to give it a rip.

Warning: Its highly addictive. If u have any problems assembling these project..I am just a few key-strokes away.

Essential Equipment: Soldering iron, preferebly 25 watts, anti static ( Rs.150), Wire stripper(Rs.25), soldering wax and flus(60/40) Rs 50, basic multimeter (Rs 200), some wires, tweezers and other stuff mentioned in the project.

Enjoy.