[Mike] picked up a cheap USB hub for four pounds (about $6) including delivery. He wanted to know how it’s possible to get quality electronics for that price, and as you may have guessed it’s not possible. He cracked open the power supply that shipped with the hub and hooked it up for some testing.

The wall wart has a sticker on it that claims a rating of 1 Amp at 5 volts. It’s pretty easy to see that this hardware cannot meet that spec just by looking at the circuit board. It’s a low-end single sided board that has some really disappointing isolation between the mains and regulated side of the circuit. As far as we can tell there’s really no reliable regulation circuit on the low side of the transformer, and the tests that [Mike] runs in the clip after the break show this. From left to right in the picture above you can see voltage at the hub-side of the power cord, current on the load, and voltage leaving the circuit board. At just 560 mA the voltage the USB hub is receiving has fallen below 3 volts!

The link to this project was sent in by [Paul] after reading about that fake Canon camera PSU. We love this kind of stuff so keep the tips coming as you find them!

[Scott's] been digging around the back issues of the Internet to find this project. He blew the dust off and sent us a link to an article that traverses the design and build process of a bench power supply.

[Guido Socher] does an excellent job of presenting his bench supply project. So many others show of the final product, but he has gone out of his way to make sure we understand the design principles that went into it. He starts off by talking about the simplest possible supply design: a transistor and Zener diode which generates a reference voltage. He goes on to discuss the problems with this simplified circuit and how to address them, covering the gotchas that pop up at each step in the process.

Once he designed the circuit and laid out some boards he began building an enclosure. We love his tip about using a stick pin and an unpopulated through-hole PCB to mark button locations on the front bezel of the case. The final design is shown above, and includes a laptop brick to translate mains power into a 24V 3A DC feed for his custom circuitry.

Concerned with your project’s power consumption but don’t want to constantly leave an ammeter wired in series with your power supply? [Rajendra] feels your pain and has recently documented his solution to the problem: a variable-output bench top power supply that clearly displays load current consumption among other things!

Everything is wired up in a nice roomy enclosure that has front-panel access to ±5V and variable outputs, an adjustment potentiometer, and even an input for an integrated frequency counter. A PIC16F689 MCU runs the show and displays the variable output voltage and current on a 16×2 character LCD. Although clearly useful as is, the PIC has plenty of I/Os and muscle left for future expansion and a capacitance meter has already been hinted at as and addition for version 2!

The power supply itself is pretty straight forward and uses 7805 and 7905 voltage regulator ICs to provide ±5V DC output. A LM350 IC also provides a variable output of between 1.25V and 9V – limited to 3V below the input voltage, in this case a rectified 12V from a standard transformer.

In order to measure current, a shunt of low but known resistance is wired in series with the output. In high-current applications these shunts are typically made of alloys that maintain a fairly consistent resistance across a wide temperature range. Since the currents in this project will be limited to a few Amperes there shouldn’t be too much resistive heating going on, and a 5 foot length of 22AWG wire wound into a coil provides a convenient and low-cost alternative. The voltage dropped across this resistance can then be measured and is directly proportional to the current flowing through it as related by Ohm’s law. This voltage drop reduces the voltage presented to the actual load as compared to the output of the regulator IC where the voltage is being measured in this case, but is accounted for in the code before the value is displayed on the lcd.

Full source code and schematics are provided and plenty of time was devoted  to explaining some of the trickier concepts such as amplifying or decreasing signal amplitudes to levels suitable for ADC input and how to use a prescaler to count high frequencies exceeding the PICs own 20MHz oscillator. Also, although this design limits the current sensing capabilities to 1.2A, alternatives to the op-amp stage are discussed that could increase this limit.

Overall this project should be very approachable to even novice hackers and is a great way to practice many basic electronic concepts. What makes it even better is that the end result is a useful tool for future prototyping.

[Will] had a cheap power supply sitting around, and decided to turn it into a full-featured benchtop PSU. Inspired by some of the other benchtop supplies we have featured in the past, he decided that he wanted his PSU to be more than just a simple-looking box sitting on his work bench. Taking some cues from PC case modding, he put together a unit that is not only very useful, but also quite sharp looking.

The frame of the case was crafted from aluminum angle, while all of the other flat surfaces were made using black polycarbonate. He installed the standard 12v, 3.3v, and 5v terminals you would expect from any benchtop PSU, complete with an LCD display showing the voltages provided by each rail as measured by an Arduino stationed inside the case. Additionally, he installed a variable terminal capable of providing 1.3v-30v, along with its own LCD display. The most unique feature is the multimeter embedded in the front of the case, which makes it virtually impossible to lose.

The case is finished off as you might expect, if you have seen any of his previous work. It features LED lighting on the inside, large fans on either side of the case for optimal air flow, and a pair of machined aluminum handles.

Be sure to check out the quick video below of the PSU being powered on.

Here’s a fancy way to convert an ATX powers supply into a bench supply. [TG] didn’t just cut off the motherboard connector and add banana plugs, but improved the functionality. Right off the bat you’ll notice that he’s added a control panel. There is an Ammeter and Ohmmeter to let you know what the unit is putting out. He added an MIC29152WT adjustable voltage regulator so that he’s not limited to the fixed voltages of the psu. As a final touch he added an external voltage probe which can be used with the flick of a switch. It’s no replacement for a proper bench supply, especially since it doesn’t have adjustable current limiting, but it’s a nice improvement upon previous psu hacks.

This is a bench power supply with adjustable voltage and current limiting. [Sylvain's] creation can regulate 0-25 volts while sourcing 0-5 amps. Current limiting is a nice feature as it will allow you to test your prototypes to ensure the power regulator you choose will not be over or underpowered.

This supply is really a two-in-one. The case has two separate circuits so that you can have different power rails going at the same time. There is a microcontroller involved, but the ATmega32 doesn’t do anything more than measure the voltage and amperage and drive the graphic LCD screen. Two potentiometers are responsible for setting the voltage and limiting the current.

[Thanks Sargonout]

[Jeri's] back with a series of videos that outlines the step-by-step electroluminescent wire manufacturing, making EL panels from PCBs, and assembling power supplies for EL hardware. These concepts are actually quite approachable, something we don’t expect from someone who makes their own integrated circuits at home.

The concept here is that an alternating current traveling through phosphors will excite them and produce light. You need two conductors separated by a dielectric to get the job done. For wire, [Jeri] uses one strand of enameled magnet wire and one strand of bare wire. The enamel insulates them, protecting against a short circuit.

But that’s not all, she also tests using a circuit board as an EL panel. By repurposing the ground plane as one of the conductors, and using the solder mask as the dielectric she is able to paint on a phosphor product resulting in the glowing panel.

Finally, you’ve got to get juice to the circuit and that’s where her power supply video comes into the picture. We’ve embedded all three after the break. It’s possible that this is cooler than blinking LEDs and it’s fairly inexpensive to get started. The circuitry is forgiving, as long as you don’t zap yourself with that alternating current.

EL wire manufacturing

Making EL panels from PCBs

EL power supplies

[Nikita] made a great find while cleaning out his garage: a set of audio amplifiers from a 1986 Volvo. After a bit of testing, he dislodged a stuck relay and set out to use these amps for a home audio system. He grabbed some left over brackets from his TV mount and used them as rail mounts. On the back he wired standard speaker connectors and RCA connectors to the wiring harness for the amplifiers. The final aspect is powering up the device, for which he used his ATX psu previously modified as a bench supply. 130-Watts of power for the cost of a few connectors.

We surprise to find we haven’t covered this common ATX bench-supply conversion before. What we have seen is an adapter to use one as a bench supply.

[Manekinen] built a power supply monitor based around an AVR ATtiny13. Voltage and amperage are displayed on a 16×2 LCD character display (we’re not sure what the third number is… samples per second?). This is no small feat considering that the tiny13 is an 8-pin chip. He makes it happen by using the pins for both LCD control and ADC input. To make this happen the HD44780 compliant display is used in 4-bit mode. Check out the video after the break and hit up the non-translated page if you want to download the source code and PCB artwork. A note of warning, he’s using the RESET pin for I/O which means once you burn the fuses you’ll need a programmer that has High Voltage Serial Programming capabilities if you want to reprogram the chip.

[Thanks RicoElectrico]

This device is lovingly called the SPINmaster. [Linux-works] built it to spin up multiple hard drives before the motherboard starts up. It detects the power-up from the PSU and uses a relay to hold the motherboard in reset, indicated by the red LED. Each of four relays then spins up a hard drive and illuminates the green LED when ready. Once all green lights come on the reset relay shuts off and the bios starts up. This type of staggered startup takes a lot of the load off of an under-powered PSU. He’s posted firmware and there’s a schematic available too. We took a look at his video but there’s not much to see as it’s just the inside of the machine while it boots up.

[Melanie] had some time this weekend so she whipped up a dual voltage power supply from parts on hand. This design plugs right into a breadboard and, unlike the last breadboard power supply we saw, provides two voltages at one time. 5v is delivered to one power bus while 3.3v goes to the other. Her design uses two linear low voltage drop regulators from the LF00 family (PDF datasheet) to accomplish this. Nice work!

[Niclas] sent us his home made tube amplifier. For the case he used a computer power supply unit, took out the guts and replaced them with the amplifier board. He based this build off of an existing design but took a more minimalist approach. The wooden face plate has an on/off switch, an audio jack, and volume control. Apparently, the tubes are floating loose inside of the case. We’d recommend a more secure mounting method for these delicate parts.

SparkFun has released a breadboard power suppy that can provide regulated 3.3v or 5v. Unlike the supply we saw from adafruit industries earlier this summer, this one is based on an lm317. This small device features on/off switch, voltage selection swith, and appropriately spaced pin headers to plug into both the top and bottom rails of a standard breadboard.  Rather build it yourself? Take a look at the schematic provided (PDF).

Every electronics workbench could benefit from having a bench power supply. Converting a PC power supply works, but often, it involves splicing wires and limits the supply to only bench use, and building one from scratch is definitely an undertaking. To counter this, [silic0re] and his father came up with a detachable adapter that simply plugs into the existing connectors. The adapter provides posts for four different voltages and can be built in no time. It’s nice to see a solution that will let you use any power supply laying around without having to worry about the dangers of opening it or cutting it up.

[Thanks silic0re]

Some companies insist on using proprietary pieces. It can be really frustrating when there is no apparent reason other than consumer lock in. It irritates us to feel like we’re being forced to buy their pieces. This is one of the more popular reasons listed when you ask a hacker or modder what got them started.  This project takes us through making a normal power supply work with the compaq proprietary 14 pin plug found in some smaller desktop PCs.

Aside from the plug itself being different, the motherboards require a 3.3v standby voltage. A normal power supply usually only has a 5v. Though there are even simpler ways of bypassing the issue, he chose to put an inline voltage regulator. Schematics are available on the site.

[via Hacked Gadgets]