Finally, the USB port on the back of your television can be tapped for something useful. [Don] is using this add-on device to automatically cut the power to his Ambilight clone. Initially, he got tired of unplugging the power adapter each time he shut off the television, so he added a switch. But laziness overcame him and he decided he needed an automatic method. After probing around on the connections available, he established that the serial interface (normally used for servicing the device) was not of any use, but the USB port is. He measured the voltage of the power bus to be 5V when the TV is on, and 0.15V when it is off. He whipped up the circuit you see above which uses the USB connection to trigger a relay, connecting power to his Ambilight clone when the television comes on, and disconnecting it when the set is switched off.

Our dream has always been an XBMC capable device that can Velcro to the back of a TV, and be powered from that USB port. Unfortunately the Beagle Board hasn’t yet made it to a stable level when running XBMC. Our next hope is the AppleTV 2, which can run XBMC but would require some hacking to get it working off of the USB port, raising concerns about how much current it would draw at 5V.

Hackaday reader [Paul] recently shared a simple hack he put together via our Flickr photostream.

It seems that his Magellan GPS unit is pretty finicky when it comes to power supplies. When connected to the Magellan adapter, the GPS unit charged as you would expect. When connected to a PC, it sensed the connection and allowed its file system to be mounted, just as it was intended to do.

However, a problem arose when he tried hooking the Magellan up to a different power supply. The unit still thought it was connected to a PC, and refused to perform any GPS-related functions since its file system was tied up. Not wanting to lug around multiple chargers, he decided to see what the heck was going on with his GPS unit.

He pulled the plug apart and found that the 4th and 5th pins of the USB cable were shorted together. While most devices ignore the 4th pin, the Magellan checks to see if that pin is grounded. If so, it assumes it is connected to its power supply. If not, it assumes that it should act as if it is connected to a PC.

With this information in hand, [Paul] did the same thing as any of us would and hacked together a USB cable with shorted pins. The cable can be attached to any standard USB port or charger, saving him from having to lug around an extra adapter.

If you work with electronics at any skill level you need juice. [Jon] has a great, and clearly worded tutorial about Wall Wart Power Supplies with pretty much everything you need to know about those little black boxes hanging off of your outlets.

The whole thing starts off with the basics like transformers, rectification smoothing and regulation, then moves on to the different basic types, dedicating a page to linear, regulated and switching types, giving output performance charts under different situations.

Also included is a run-down of DC barrel jack structure so you get the right plug every time, wall wart type identification, a random sample comparison test, and a good selection of formulas to even keep the old hats reading along. Although you might want to set aside a little time at 9 pages and some Q/A in the comments, it might take a moment to read.

[Marc] is pretty unsatisfied with hard drive docking stations as a whole. He says they are typically slow and unreliable, causing him all sorts of grief while he is troubleshooting a questionable hard drive. He decided to take some of the mystery out of the troubleshooting equation and built a standalone SATA power module.

Aware that SATA drives require 5v and 12v for operation, he disassembled one of his docking stations to see how it provided both voltages. He discovered that it used a simple PWM buck converter and decided to replicate it in the smallest space possible. His plan was to use a standard 12v wall wart to power the circuit, passing that 12v straight to the drive. A simple voltage step-down circuit would be built to provide the required 5v.

[Marc] reports that the power adapter is performing nicely, and he is quite happy with the size as well. He says that one major benefit of this sort of adapter is that it can be used to power any SATA drive, not just hard drives. He does mention that if he built another one, he might consider regulating the 12v output as well, so that he can power the adapter with a laptop power supply instead of a separate dedicated wall wart.

What can you do to make sure your system is running as efficiently as possible? Take a page out of [Mux's] book, who went to great lengths to measure and adjust his system for ultimate efficiency (translated). What he ended up with is 8.5 Watts of consumption at idle and about 50 Watts under load. Luckily he posted a six-part series with all of the details.

Some of the changes he made were in software, like reducing voltage to certain hardware by adjusting BIOS settings, and installing display drivers that put the screen into the proper sleep mode. Others were hardware changes like swapping out the power supply with a hacked PicoPSU and removing unnecessary parts from the motherboard like the MAX232 com-port chip. Looks like we need to audit our always-on MythTV box and see if we can apply any of these power-saving techniques.

[Thanks Gijs]

New Years celebrations tend to get bigger and bigger every year for most people, and [Brian] takes no exception. In order to top his lighted tree of a few years ago, he has concocted a 40′x40′ set of Seven-Segment displays made out of Christmas lights, hung from nearby trees. These displays would start counting down the minutes an hour before the ball drop, and be synchronized with music. Also in the spirit of a New Years party, the music he has chosen is in the form of a Power hour. The control board [Brian] is using also comes with two extra outputs, which he plans to use for the most exciting possible additions: Fireworks and Flamethrowers.

Be sure to check back after New Years to see a video of the device in action. Be sure to Hack, Drink, and Party Responsibly out there.

[Riley Porter] posted a picture of his EvalBot USB power hack. In the photo above we’ve put a box around D6 and D7. The development board ships with a 0 Ohm resistor in the D7 location, patching in power from the USB-B connector labeled USB DEVICE. He found that by moving that resistor to D6 he can power the board from the USB-B connector labeled ICDI.

That connector is the In-Circuit Debug Interface. TI sent us an EvalBot bundle so we pulled it out and tried it ourselves. If you plug in the ICDI it doesn’t power the board, and no USB devices register. Shorting the D6 pads changes this and the following USB device registers:

Bus 002 Device 062: ID 0403:bcd9 Future Technology Devices International, Ltd Stellaris Evaluation Board

So it looks like you need to have two USB connections or be using batteries in order to program the board via USB. The uC/OS-III hardcover book that ships with the EvalBot bundle includes board schematics. We took a look and were surprised to see that they show diodes installed on both pads. Rev A of the online schematics have been corrected, showing an omitted diode on D6 and the 0 Ohm resistor on D7. Images of both schematics are included after the break.

It would have been nice to see a selector switch installed here to give you a little more flexibility when prototyping.

Schematic from uC/OS-III page 700:

Stellaris Robotic Evaluation Board Schematics Rev A (available here):

[Warrior_Rocker] pulled off his own Apple Studio Display hack by removing the cable and adding ports. As we saw in Wednesday’s post, these displays use a cable with a proprietary connector that combines DVI, USB and Power. Instead of altering the cable, [Warrior_Rocker] removed it completely. By wiring up a standard barrel jack for power, a USB type-B socket, and a DVI port, he can now use standard video, power, and USB cables to connect to the monitor.

This project was actually submitted to us on May 25th and we missed it. It’s sad that sometimes tips fall through the cracks, and we’re sorry that we missed this particularly well-executed hack. [Warrior_Rocker] wrote in asking why his project didn’t qualify after seeing the similar post on Wednesday. So please don’t take it personally if your project doesn’t get posted. If you think it fits right in here at Hackaday and haven’t heard anything after two weeks or so, consider sending to us again.

This programmable power supply is the perfect addition to your bench tools. [Debraj Deb], who previously built a whole house power monitor, designed this build around a PIC 18F4520 microcontroller. The desired voltage is set with an attached keypad, resulting in a digital output on the 8-bits of port D. The port connects to another protoboard with an R-2R digital-to-analog converter resulting in the target voltage. A set of transistors amplifies the current and a power transistor then takes care of the final output. After the break you’ll find two videos, the first walks us through the hardware and the second demonstrates the device in action, along with measurements of its performance. This certainly provides a lot more functionality than an ATX power-supply conversion.

Update: A big thanks to [Debraj] who sent us a code package as well as the schematic (PDF) used during testing. We’re having trouble getting the code package up for download right now. Check back later, hopefully we’ll have it up soon.

Part 1

Part 2

[Debraj Deb] put together a current monitoring device that interfaces with the circuit box at his house. The system is controlled by a PIC 18F4520 and uses an LM358 Op-Amp to rectify the AC signal, as well as an MCP6S21 for range adjustments for detecting both high or low current loads. The data displayed on a character LCD includes average, RMS, and peak current. For now the data is saved to an EEPROM and can be dumped using a serial connection but [Debraj] plans to add a GSM modem so he can send energy use data to his cell phone.

[Thanks Ganesh]

Reader [Tim Upthegrove] sent in a novel take on powering and monitoring AC outlets and devices called SPRIME, or Simple Powerline Remote Interactive Monitor and Enforcer. Compared to previous hacks, such as 120v switching or Quick cheap remote outlets, that only turned an outlet on or off; SPRIME allows not only control over outlets via the internet, but also power usage of devices currently plugged in.

We really liked their idea of giving power companies access to SPRIME outlets to reduce power consumption during peak hours, but sadly we don’t see it being implemented in homes any time soon. Catch a video of SPRIME after the rift.

[Thanks Chris McClanahan and Jeff Starker for the project, and deyjavont for pointing out our silly mistakes]

Update: This How-To was written for April Fools’ Day. It is not advised  you attempt to make or even use this cable. The comments have made it very clear how dangerous to you and others using this cable can be. The image above is not of a full male-to-male cable, only the ground is connected, and the generator is not running.

We all know Ethernet has the crossover cable, cars have jumper cables, and RS232 has the null modem. Well, it is about time our wall sockets get their own crossover cable. This crossover cable is great for running power to a circuit disconnected from power. Maybe you are out of fuses, the breaker is broken or you just don’t want to go check the fuse box when there is a murderer about. This cable makes a great gift for even the most loathsome of acquaintances.

This an April Fools’ Day post. You should not do this!!!

Warning: These are Mains voltages and currents we are working with. If you do not know why you should not attempt this, you should not attempt this.

You will need:

• 1 Extension cord.
• 1 Male extension cord repair connector.
• Tools to strip the extension cord, and attach the connector: Knife, wire strippers, and screwdriver.
• Respect for mains voltages and currents.

If your extension cord has warning labels, read them.

Cut the extension cord to the desired length.

Strip about one inch (2.5cm) of the outer insulation from the part of the cord that has the male plug.

Strip about 3/8 inch (1cm) of each of the conductors. If there is a strip gauge, use it for a guide instead. Twist each of the stranded conductors to prevent fraying and possible shorts later.

Slide the shroud over the cord.

Screw the conductors into each of their respective terminals on the connector.

• The Green or bare conductor goes to the ground conductor terminal. It often has a green screw.
• The White conductor goes to the grounded conductor terminal. It often has a silver-colored screw.
• The Black conductor goes to the ungrounded conductor terminal. It often has a gold-colored screw.

Use a multimeter to check continuity and make sure there are no shorts.

Slide the shroud up to the connector and fasten the two parts together.

Secure the cable clamp.

There you have it, a finished Mains crossover cable.

There you have it, a Mains crossover cable. How might you use this crossover cable?

[Freeload] sent us his custom MagSafe adapter build for laptops. MagSafe for those unaware is Apples (patented) power adapters that prevent damage to laptops when the cord is accidentally yanked from the socket. While we’ve seen some custom versions before of MagSafes they were usually bulky, ugly, and used a ton of unremovable glue. We really like [Freeload's] because its quick, good looking, and the best part – completely removable without marks or damage. In short, an easy weekend project that could one day save your laptop.

[Kenneth] built a 5v controlled power outlet inside of a junction box. We’ve seen plenty of projects that can switch 120v outlets using 5v logic for refrigerator controllers, lighting controllers, or grow systems, but they almost always use solid state relays to facilitate the switching. This iteration uses mechanical relays along with the necessary protection circuitry. The project is housed in an extra deep single-gang box and allows for individual switching of the two outlets. You can see this connected to an Arduino switching two lamps after the break.

[Thanks Mightysinetheta]

[Rosenberger31] did a nice job of adding a USB port to his 2010 Toyota Prius. He removed the access door on the console where the traditional “cigarette lighter” 12 volt port is located. A Dynex 12-volt to USB adapter was piggy-backed onto the power lines and the USB connector was then fit into the blank accessory plate next to it.

There is no data connection here, the port only provides 5v regulated power to devices plugged into it. None the less, it is still a pretty nice looking alternative to having a power adapter hanging out of the dash all the times. If you try this, heed one of the warnings from the comments and make sure you add a switch if you vehicle powers the 12 volt port even when the car is not running.

This makes us wonder: will this void your warranty?