Month: August 2012

Bluetooth Control In A Power Strip

August 28, 2012 by 16 Comments

[Mansour] had a ceramic space heater mounted near the ceiling of his room. Since heat rises this is not the best design. He upgraded to an infrared heater which works a lot better, but lacks the timer function he used on the old unit. His solution wasn’t just to add a timer. He ended up building a Bluetooth module into a power strip in order to control the device wirelessly. He ends up losing all but two outlets on the strip, but everything fits inside the original case so we think it’s a reasonable trade-off.

He uses relays on both the live and neutral wires to switch the two outlets. These are driven via MOSFETs to protect the ATmega168 which controls the board. The microcontroller and Bluetooth module both need a regulated DC power source, so he included a transformer and regulator in the mix. After the break you can see him demonstrating the system using two lamps. There’s even a terminal interface which lets you select different control commands by sending the appropriate character. This interface makes script a breeze.

At least this power strip doesn’t spy on you.

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Turning On PC Speakers Whenever There Is Music Playing

August 28, 2012 by 44 Comments

If you’re like a lot of people, most of the time your computer speakers are on without actually playing any music. This wastes a bit of power, and [Bogdan] thought he could create a circuit to cut down on that wasted electricity. The result is a very tiny auto-on circuit able fit inside a pair of speakers.

The circuit is built around the ATtiny13, very nearly the smallest microcontroller available with an on-board ADC. When music is played on the computer, the ATtiny senses a bit of voltage in the audio line and switches a relay to power the speaker.

Of course, there is always the problem of music with a high dynamic range; if the sound played from the computer has too low of a volume, the ATtiny might turn the speakers off even if music is playing. [Bogdan] solved this problem by adding a timer to his code; if nothing is detected by the ADC for three minutes, the speakers turn off.

Robo Doc Reads Children’s Pulses Without Scaring Them

August 28, 2012 by 25 Comments

[Markus] recently took his 14-month-old daughter to the pediatrician for a routine checkup. During the examination, the doctor needed to measure her pulse and quickly clamped an infrared heart rate monitor onto her finger. Between the strange device clamped to her finger and incessant beeping of machines, [Markus]’ daughter got scared and started to cry. [Markus] thought these medical devices were far too scary for an infant, so he designed a funny robot to read an infant’s heart rate.

[Markus] liked the idea the Tengu, a robot with a LED matrix for facial expressions, and used it as inspiration for the interface and personality of his RoboDoc. To read a child’s pulse rate, [Markus] used a photoplethysmography sensor; basically an IR LED and receiver that reflects light off a finger bone and records the number of heartbeats per minute.

The build is tied together with a speaker allowing the RoboDoc to give the patient instructions, and a servo to turn the head towards the real, human doctor and display the recorded heart rate.

We think the RoboDoc would be far less disconcerting for an infant that a huge assortment of beeping medical devices, and we can’t wait to see [Markus]’ next version of non-scary doctor’s tools.

Soft Robots Given Veins The Let Them Change Their Stripes

August 28, 2012 by 21 Comments

If it were alive this robot would be classified as an invertebrate. It lacks a backbone and interestingly enough, all other bones are missing as well. The Harvard researchers that developed it call it a soft robot. It’s made out of silicone and uses pathways built into the substance to move. By adding pressurized air to these pathways the appendages flex relative to each other. In fact, after the break you can see a video of a starfish-shaped soft robot picking up an egg.

Now they’ve gone one step further. By adding another layer to the top, or even embedding it in the body, the robot gains the ability to change color. Above you can see a soft robot that started without any color (other than the translucent white of the silicone) and is now being changed to red. As the dye is injected it is propagating from the right side to the left. The team believes this could be useful in a swarm robotics situation. If you have a slew of these things searching for something in the dark they could pump glowing dye through their skin when they’ve found it. The demo can be seen after the jump.

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Learning The Ins And Outs Of USB With A Simple Dev Board

August 28, 2012 by 17 Comments

We can’t count the number of projects we’ve seen on Hackaday with a USB port.  Unfortunately, most of these builds – from RepRap controllers to wireless data loggers – don’t use the full capabilities offered to them with USB. [Ben] came up with a very cool USB breakout board that allows you to explore the USB protocol with just a single inexpensive ATtiny.

Instead of relying on an FTDI chip or otherwise sending serial data down a USB pipe, [Ben]’s project is meant to be the hardware compliment to his book on programming USB devices. His hardware board is exceedingly simple, just an ATtiny 2313, a USB port, and a handful of other components, but allows [Ben] to receive data on eight pins on a breadboard and send them over USB to a computer.

[Ben] had sent in his USB figure eight controller, a board that displays the numbers 0 through 9 according to what data is received via USB, a while ago. It’s a truly useless build aside from learning how USB works, but an excellent tool if you’d like to program your own USB device.

Turn Your Old Bluetooth Headphones Into A DIY Car Audio Receiver

August 28, 2012 by 11 Comments

wireless-car-audio

[Tim] drives a 1995 Mitsubishi TS Magna, which is equipped with a less than stellar accessory package he lovingly calls a “poverty pack”. He outfitted his ride with an aftermarket head unit that can support the Bluetooth A2DP profile, provided he buys the ridiculously overpriced kit sold by Pioneer. Reluctant to shell out more money on an audio kit than his car is worth, he whipped up his own Bluetooth kit for far less than Pioneer’s asking price.

He had a set of Nokia Bluetooth headphones that he was willing to part with, so he disassembled them to see how he might interface with his car stereo. Connecting the headset to his head unit was a relatively easy task, but he had to work a bit harder to get his Bluetooth receiver powered properly.

After both undervolting and then nearly cooking his wireless audio rig, [Tim] managed to get things operating to his liking. He says that the audio is a touch quieter than he would like at the moment, so he will likely be revising his design in the near future. For now however, he can stream tunes from his phone while he cruises around town.

BGA Soldering With A Paint Stripper And Stopwatch

August 27, 2012 by 22 Comments

Having just received a shiny set of PCBs from the fab-house [Devbisme] needed a way to solder the main chip in place. It has a Ball-Grid Array footprint which is notoriously difficult to populate in a home lab. But he makes it look pretty easy and decided to share a video tutorial of the process.

The main tool he used is the paint stripper (heat gun) seen above. Since he didn’t have his own fancy reflow oven he made things work with the gun as his heat source. First he applies a generous layer of liquid solder flux to the BGA footprint on the board. Next he melts some solder onto the tip of his iron and uses it to tin all of the board’s BGA pads. Then it’s time for the critical step of positioning the chip. He uses vacuum tweezers to set it in place, and traditional tweezers to fine-tune its position. From here he heats with the paint stripper for two minutes, starting far above the board and slowly moving closer, with the reverse at the end of the soldering process. Once cool the board is cleaned with distilled water and blown dry with compressed air. After a visual inspection he finishes the application with a 30 minute stay in a 300 degree oven. We’ve included the video after the break for your convenience.

We’ve seen a similar technique used for replacing a chip on an already populated board.

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