Software-Controlled Per-Port Power Switching For USB Hubs

February 5, 2014 by Kristina Panos 34 Comments

[Befi] wanted to add a second stage backup disk to his ODROID embedded-board server, which typically draws ~1.5W at idle. After adding the disk, he saw power consumption increase by 2W when the new disk wasn’t spinning. He thought about using one of those USB hubs with the adorable little rocker switches for each port and replacing them with transistors, but that was going to be messy. After some poking around in the USB standard, he found that most support per-port power switching (PPPS), and set about to hack a USB hub to enable software-controlled per-port switching.

[Befi]’s NEC hub uses a uPD720112 chip which supports PPPS according to the datasheet. After tying the configuration pin labeled GANG_B to +3.3V, the hub declared itself PPPS-compatible. Of course, the manufacturer saved a penny or two by omitting the individual switches, so [Befi] added an open-drain NMOS to each port. He is using this program to switch the port on and off and made the switching transparent with autofs. [Befi]’s current script has the bus ID and device ID of the hub hard-coded, but he intends to update it to find them automatically. This hack saves him 10W on average, which is about €30 ($40) per year.

If your hub is under powered, you could try adding an external power supply.

Tic Tac PIC Pack: A Pocket Programmer

February 5, 2014 by Kristina Panos 10 Comments

Sure, mint tin housings are great. But you have to defend against shorts, and cutting out holes for ports and buttons is dangerous business. [Daniel] prefers plastic, and he tipped us off about a PICKit2 clone that he designed to fit inside of a tic tac box.

Almost all of the components were salvaged except for the microcontroller and the connectors. He wound his own inductor using the ferrite core from a CFL. [Daniel] had to make a few improvisations for this project. He didn’t have a 20MHz crystal, so he used a 12MHz crystal and tweaked the fuse bits after burning the firmware.

To save space on the board, he soldered wires to RESET, VCC, GND, PGD, and PGC to program the firmware and then removed the wires. The only trouble he had with it was more or less easily solved by replacing two transistors.

You may remember that we linked to his USBasp programmer in a mentos container a few months back. We figure [Daniel] must have some pretty fresh breath.

Hacking An Escape From East Germany

February 2, 2014 by Kristina Panos 40 Comments

Some hacks are just for fun. Some make your job or your life easier. Once in a great while, a hack will save your family from an oppressive government. This is the kind of hack that [Günter] pulled off when he and [Peter] built a homemade hot air balloon to escape East Germany and the oppression of the Stasi in 1979.

Like many East Germans who weren’t in line with the Party, [Günter] found life unsatisfactory on his side of the Berlin Wall. Travel, job options, and freedom of expression were all severely limited. Aside from joining the Communist Party, the only option seemed to be escape to West Germany.

[Günter] and his wife [Petra] were inspired when [Petra]’s sister, who had escaped in 1958, came to visit. She brought with her a newspaper that covered the International Balloon Fiesta in Albuquerque, New Mexico. [Günter] and [Peter], whom he worked with, decided that they would conspire to build a hot air balloon capable of transporting them, their wives, and their four children across the border.

Theirs is an incredible story fraught with adversity. They ended up constructing three different balloons, all the while traveling further and further from home to avoid suspicion when buying large quantities of fabric. They had a lot of trouble finding the right propulsion method and ended up using pure oxygen. During the narrow window they had before [Günter] was due to report for military duty, the weather was unfavorable except for a short period after a front had passed through. They had no time for testing and just went for it.

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Are We Not Indestructible? We Are Quiz Buttons!

January 31, 2014 by Kristina Panos 14 Comments

In what we hope is a new trend in interviewing, some of the people at [Anthony]’s place of work asked him to make some wireless quiz buttons. He took the task quite seriously, making them extremely robust and low-power.

[Anthony] is experienced in the button arts, having made this party push button for a wedding reception. His design for the quiz buttons is a little different. Each button has an Arduino Pro mini and an nRF24L01 wireless RF module. On the receiver side is an Arduino Pro micro and an another RF module. A connected PC captures the serial data and displays the pressed button’s ID. It also shows the order in which subsequent buttons were pressed and the time elapsed between them.

The really notable part of this build aside from the awesome laser-cut MDF Devo energy dome button housings is the extremely low power consumption of the transmitting Arduinos. [Anthony] has designed them to go into sleep mode which disables all on-board circuitry and only wakes on interrupt. He removed the power LED and the voltage regulator since they run on 2-AA batteries. The voltage regulator was drawing more than 25mA in sleep mode. Because of these mods, each button consumes < 1μA, which is less power than the batteries can self discharge over their lifetime.

[Thanks Jef]

Heatsink Tester Shows Thermal Resistance Isn’t Futile

January 29, 2014 by Kristina Panos 13 Comments

[Bogdan] knows that it’s hard to model the cooling needs of any given project. It’s important to know how much heat a system can dissipate given the housing material, airflow opportunity, and the proximity of neighboring components. Inspired by an aluminium-walled enclosure that allows for mounted transistors, he devised and built a heatsink tester.

He’s using an ATXMEGA32A4U, a temperature sensor, and a IRF540 MOSFET. A specific power is dissipated across the transistor, and the temperature sensor measures the heatsink as close as possible to the transistor. Through the serial connection, he gets back the supply voltage, current, calculated power, DAC set, temperature, and calculated thermal resistance in the terminal.

[Bogdan]’s tester assumes that it is reading the ambient temperature, so the circuit needs to warm up first. He found that an hour is generally long enough to reach this point. He also found that the system exhibits high thermal inertia, so it regulates the DAC output based on the dissipated power.

Stop Traffic In This 7-Mode LED Running Jacket

January 27, 2014 by Kristina Panos 35 Comments

[Miria] was tired of tangling with bicyclists on her nighttime runs. It was obvious to her to illuminate herself, but she thought it would be really cool if the lights responded to her heart rate. The short summary that tipped us off is over at NYC Resistor, and [Miria] gives the gory details on her blog. The LEDs operate in seven different light modes that increase in speed proportionate to her heart rate.

She started the build around an Arduino but found that the compatible heart rate sensors were mostly optical and gave inaccurate readings. Since she was already using a Garmin GPS watch and heart rate monitor band, she decided to hack into the conversation between the two. Garmin uses the ANT protocol for this. While [Miria] found the documentation to be an effective sleeping pill, she also found that SparkFun has an ANT transceiver breakout board. Unfortunately, it’s been discontinued.

[Miria] continued undeterred, using the SparkFun board for prototyping. Her final version uses a Teensy 2.0 and this ANT transceiver in place of the ill-fated SparkFun board. She found an Energizer power pack that plugs directly into the Teensy and can power both Adafruit weatherproof LED strips for about an hour. Look both ways, and check out her demo after the break.

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How To Stop Grandma’s Wheelchair If She Goes Out Of RC Range

January 26, 2014 by Kristina Panos 26 Comments

Okay, so he doesn’t have Grandma riding in it that we know of, but [zim] recently decided to turn a Jazzy mobility chair into “a radio-controlled platform for mischief”. RC offers more range than wifi or bluetooth, and he was able to find a reasonably priced secondhand radio on Craigslist. However, he found out that in the event of signal loss, the receiver keeps sending the last commands to the speed controller. [zim] didn’t want his 150 lb (68kg) mischief platform getting loose, so he devised a fail-safe that cuts power to the motor when the signal is lost.

[zim] discovered that the receiver returns channel 3 (the throttle) to a preset condition whenever the signal is lost. He used a 24V HVAC relay controlled by an Arduino Nano to sample the PW on channel 3 and shut it off when either the throttle or the signal are cut.

If Grandma is feisty, you could build this caged-in version with a shopping cart.

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