Hackaday Links: August 12, 2012

License plate tablet rack

[Hunter Davis] used an old license plate as a tablet stand. It loops around the leg of his laptop table and has a cutout for the power cord of the tablet.

More power power wheels

It may look stock, but this power wheels is hiding a new frame, motors, and tires. You won’t see it in the Power Wheels Racing Series, but it is a ton of fun for this lucky kid.

Surveillance camera chess

Want to play a game? A yellow briefcase hijacks surveillance camera feeds and lets those monitoring them play chess via text message.

ATX bench supply looks like a bench supply

Here’s another rendition of an ATX bench supply. [Ast] rolled in a voltmeter for the variable voltage plug, and an ammeter to finish off the hack.

Lync auto-responder to fool the bossman

In a move reminiscent of [Ferris Bueller], [Sepehr] coded a Lync auto responder to answer the boss when he sends an IM.

Giving an ATX bench supply the case it deserves

Your bench supply doesn’t need to look sad just because you’re using an ATX power supply instead of a commercial product. Follow [Ian Lee’s] example and you could have beautiful wooden enclosures for the tools in your own shop.

The woodworking skills used here aren’t all that advanced, but you need to have a knack for it so we suggest running some test pieces before you start the actual build. [Ian] ran a dado for the front and back panel in each piece of the wood sides. At each corner the inside of the the pieces were mitered at 45 degrees. To put it all together he laid the pieces end to end on a the work bench, then applied painters tape to the outside of the joints. This holds the joints together so that he can flip the collection over, apply glue, and then start hinging the sides into place. It’s almost like rolling up a box.

As with other ATX supply projects we’ve seen [Ian] designed this so that the PSU can be swapped out later if necessary. Instead of wiring his own cable harness he used an ATX breakout board. To get the interface layout he wanted he mounted the banana jacks separately and just ran jumper cables back to that board.

Bench supply built in a power strip

Back in his college days [Print_Screen] grew tired of always building a power supply on his breadboard. To make prototyping quicker he came up with the bench supply that is build into a power strip. This one is using linear regulators for power, and create much less noise on the lines than a supply made from a switch-mode PSU.

First thing’s first, he needed to step down from mains voltage and rectify the AC into DC. He gutted the smallest adapter he could find and managed to fit it into the gutted power strip. It puts out 15V which will work perfectly for the regulators he’s chosen. Each one gets its own slot where an outlet is on the case. The ground hole has been plugged by a toggle switch which routes power to the free-formed regulator/capacitors/heat sink modules. There is a slot for 15V (coming directly off of the converter), 10V, 5V, 3.3V, and two variable regulators which are controlled by the knobs above the outlet. We’ve never seen anything like this and find it most excellent!

[Thanks OverFlow636 via Reddit]

Building a bench supply without altering the ATX psu

[FozzTexx] has been using a bench supply he made from an AT PSU for years. He put a lot of work into that one, removing unnecessary wires, mounting banana plug jacks on the metal case, and adding an on/off switch and labels. But if it ever dies on him it will be a major pain to do all that work again in order to replace it. When he set out to build another bench supply from an ATX PSU he decided to do so without altering the PSU. This way he can easily swap it out for a different one if he ever needs to.

The hardest part of the hack was sourcing connectors. But with the parts in hand he’s able to just plug the faceplate into the stock connector. This gives him access to all of the voltages, and provides an on/off switch and indicator light. He might also want to add the option of resetting the unit if the over-current protection kicks in.

Quieting an inexpensive bench power supply

[Mike] just purchased this Atten APS3005S bench power supply for around $80. It does the job, but boy is it noisy! We were pretty surprised to hear it fire up in the video after the break. To make matters worse, the noise is persistent since the fan never shuts off. Having worked with other bench supplies he knew that a common feature included in many models is temperature controlled case fans. He set out to quiet the fan and implement a temperature switch.

For this project [Mike] had the benefit of looking at a nearly identical model that does have temperature switching. He discovered that the board on this one has a through-hole zero ohm resistor populated in place of a thermostat switch. That switch closes the connection at or above 45 degree Celsius, thereby turning on the cooling fan. Bridging the traces with a zero ohm resistor to save on production costs is what caused the fan to run continuously. After replacing the resistor with a KSD-01F and swapping out the stock fan for a high-quality version [Mike] has takes a noise maker and turned it into a device that’s kind to the ears.

Continue reading “Quieting an inexpensive bench power supply”

Designing and building a bench supply

[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.

DIY digital bench power supply

[Guido Socher] built himself a great little bench power supply that’s able to put out 30 Volts at 2 Amps.

Instead of taking the easy way out by putting a few taps on an ATX power supply, this project was built around a generic 24 Volt laptop power brick. An ATmega8 generates a PWM signal that is sent though a low-pass filter, allowing everything to be very precisely controlled. This DC signal is then sent through a BD245 power transistor to bring everything up to the desired output. [Guido Socher] included a USB port for computer control of everything, and the final project is something we’d be happy to have on our bench.

We’ve seen a few computer power supplies converted into a bench power source, but we’re impressed with [Guido Socher]’s build log. It’s not often we see a hack that goes over the theory of operation, and the end product is very nice (and functional) too.