Building A Bipolar Supply From A Boost Converter

This DC-DC Bipolar PSU was developed for use with a guitar effects pedal. [Obsolete Technology] needed to source both positive and negative 15V. This is pretty easy to do if you’re converting from mains, but he wanted a solution that could work with a lower-voltage AC/DC wall wort or even from batteries.

The part that pulls it all together is the LT3467. It’s a switching power regulator which offers a range of features configured by the layout of a handful of external passive components. It can put out 80 mA on each line (positive and negative). Also extremely useful for this application is the chip’s high frequency operation. Depending on the version, it switches at 1.3 or 2.1 MHz. This is high enough that it will not introduce audible noise into the audio system.

We’ve got an exercise bike whose negative supply for the LCD is blown. We’re going to try build this circuit, trimming it for our voltage needs, and get the contrast working again.

[Thanks Olli]

PCA9517 I2c Translator A Perfect Companion For Raspberry Pi Hardware Add-ons

The rig pictured above works as an Internet connected temperature sensor which sends [Zaion] an email with a graph of the change over time. This in itself is interesting, but one part in particular caught our eye. He’s using an i2c temperature sensor , and we think the PCA9517 Level-Translating I2C Bus Repeater that makes it possible is a perfect match for the RPi.

This is a Texas Instruments part. You can find more about it from the company’s product page. The key words in the name of the chip are ‘Level-Translating’. This has two bus connections, each with variable voltage levels. On side A the bus can be 0.9V to 5.5V. On side B the bus range is 2.7V to 5.5V. Since the Raspberry Pi I/O pins operate at 3.3V this could connect to the B side, give you the ability to interface with i2c parts rated for lower or higher voltages. This is especially handy for folks who started with the Arduino and own mostly 5V compliant prototyping hardware.

The part comes in a SOIC package, which you can easily hand solder and will costs around $1 depending on the supplier.

Parts Storage For All Your Components

When [Steve] saw that we requested reader’s solutions to storing hundreds of different components, he had to send in his solution to storing bunches of ICs, resistors, transistors, and other components.

Like most of the suggestions we’ve seen, [Steve]’s solution relies on #10 envelopes stored in boxes specifically designed for holding envelopes. While there’s nothing new about storing handfuls of ICs in envelopes, we really like [Steve]’s method of organization.

On the top of each envelope, [Steve] printed a bunch of very useful information including the type and kind of part, the tolerance, speed, voltage, and package information. Also included are the manufacturer and vendor part numbers, making reordering a breeze.

Of course printing out hundreds or thousands of envelopes with this information would be a pain. [Steve] got around that by automating the process with iWork, typing in the values for each field in a spreadsheet app and using Mail Merge to print them all on envelopes.

It’s a very neat system that forced [Steve] to have all his parts on a spreadsheet, inching ever closer to a complete inventory management system. He’s thinking about adding QR codes to the envelopes to make reordering parts trivial, but after figuring out how to send hundreds of envelopes through a printer, we can understand if [Steve] wants to be a little lazy from here on out.

[ch00ftech] Visits A Shenzhen Market

On a business trip, [ch00ftech] visited a Shenzhen electronics market and documented the trip. Some of the attractions included multiple Apple stores of questionable authenticity, stores selling PC components with no manuals, drivers, or packaging, and a variety of LEDs and lasers.

[ch00ftech] showed off the loot from the trip, including breadboards, perf boards, LED matrices, and an RFID reader all for very low prices. There’s also the Class 4 laser pointer that cost about $120 and has a power output of “between 500 mW and 8000 mW.” Given the 500 mW power restriction on lasers sold in the US, it’s fair to say that this thing should be handled with care. Hopefully the included safety classes actually block the specific wavelength of the laser.

The staff in these stores were very knowledgeable and knew part numbers and inventories by memory. One of the biggest surprises was just how low the prices were.  While Radio Shack has started to carry some more parts for hackers, it seems that nothing stateside can compare these Chinese electronics markets.

Switch Mode Breadboard Supply From A PTH08080

[Ben] wanted a switch mode power supply for his breadboard. He ordered a PTH08080 module which is made by Texas Instruments. The spec sheet would make it a great choice for him, but he was not happy to learn that the pinout doesn’t conform to the 0.1″ spacing used by solderless breadboards. His solution was to make a breakout adapter from some protoboard.

The PTH08080 can source up to 2.25A. It accepts 4.5-18V input and can output 0.9-5.5V. The best part is the efficiency that a switch mode supply achieves compared to linear regulators. This design adds in two capacitors which are suggested in the application circuit from the datasheet (PDF). Notice that there are two headers on the breakout board. One supplies power and ground to the breadboard. The other gives him a place to connect the adjustment resistor used to select the output voltage. This connects between one pin on the PTH08080 and GND. [Ben] plans to upgrade the design by included a precision trimpot for easy output voltage adjustments.

Hackaday Southwest Tour

Earlier this summer, I took a trip through the southeast of the country. On this trip I was able to visit several hackerspaces and meet some really great people. We started at Squidfoo in Springfield Missouri. Then Moved on to Makers Local 256 in Huntsville Alabama. After that we saw 7hills hackerspace in Rome Georgia as well as Freeside hackerspace in Atlanta Georgia. The final leg of the trip took us to Chatt*Lab in Chattanooga Tennessee and the Hacker Consortium in Nashville.

For this trip, I am taking my family to the Grand Canyon. Well, that’s the part the kids are looking forward to. I’m looking forward to more hackerspaces and fantastic people. If you’re along the route from Springfield Missouri to Flagstaff Arizona, let me know (we’ll be hitting roswell NM on the way back too). We can go a little out of our way, but not hours.  I would really love to visit some hackerspaces on this trip and do a video tour. You can comment here or hit me directly at caleb@hackaday.com.

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Making Flex Sensors On The Cheap

When [Michelle] was making a sign language translation glove, she needed a bunch of flex sensors. These flex sensors cost about $10 a pop, meaning her budget for the project was eaten up by these bendy potentiometers. Since then, [Michelle] figured out a great way to make extremely inexpensive bend sensors using anti-static bags and masking tape, allowing her to start her project once again.

The build works by sandwiching Velostat plastic bags – the same electrically conductive bags all your components arrive in – between layers of masking tape. A jumper wires is attached to a strip of Velostat attached to a piece of masking tape. Between two of these anti-static/masking tape assemblies, another piece of Velostat is placed. After laminating all these pieces together, [Michelle] had a primitive yet very functional flexible potentiometer.

After attaching one of these flex sensors to an analog input of her dev board of choice, she had a wonderful and inexpensive flexible sensor. You can check out this sensor in action after the break.

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