Modifying A Knock-off Battery Charger To Be Safer

September 16, 2013 by Phillip Ryals 30 Comments

Sometimes buying a low-cost clone off of eBay is a great option, but [Martin] wisely decided to test his counterfeit IMAX B6AC, and found it grossly lacking. His detailed breakdown shows an alarming array of problems, including poor design and construction, and a lack of warning if the balance circuit fails. In addition, the charger wasn’t properly calibrated. By using a precision multimeter, Martin found that the charger actually brought cells above critical voltage. So really, using a charger like this out of the box can both destroy your battery pack and/or start a fire. One other interesting detail – this model can only be calibrated once. Sweet features.

[Martin] detailed his fixes in a well-illustrated blog post. He first had to re-enable the calibration menu using this method which requires bricking the device first! Once un-bricked, however, he could do the recalibration using a voltage divider and a reliable power source.

This project really underscores the need for a precisely calibrated multimeter. Not only would [Martin] not have been able to test his charger properly, but the re-calibration wouldn’t have been as accurate as needed. As hobbyists, this is a reminder that we can only trust our tools if they are accurate.

Organizing Transistors

September 14, 2013 by Brian Benchoff 10 Comments

SAMSUNG

Late last year, [matseng] set up an interesting challenge for himself: design a new PCB every week, send it off to a fab house, and build a new project. It’s a grueling endeavor, but some of these projects are actually very useful and cool. One of the best so far is the TraId – a board that identifies a transistor type and pinout with a nice LED interface.

This build was partly inspired by Dangerous Prototypes’ Part Ninja, a board that determines the pinouts and values of transistors, resistors, caps, and diodes. The TraId is a much more cut down version usable only for transistors, displaying the orientation of the pins and type of transistor on a set of 8 LEDs.

Although the design is very sparse, we could imagine something like this being very useful in a hackerspace, lab, or anywhere else the gremlins of chaos come to reorganize parts drawers. If you’d like to build your own, all the required files are up on the gits.

PCB Agitator From A Broken CD-ROM Drive

September 10, 2013 by Mike Szczys 49 Comments

pcb-agitator

Etching PCBs goes a lot better if you agitate the solution in order to carry away the dissolved copper and get fresh etchant to the area. With that in mind [Rohit Gupta] designed a mechanism in Sketch Up before realizing he was going about it the hard way. He ended up basing his agitator on a broken CD-ROM drive instead of starting from scratch.

He uses the CD sled from the drive, ditching the lens and its support structure. To get direct access to the motor that drives the tray he uses an L293D H-bridge chip. This is controlled by an MSP430G2231 microcontroller. The driver board seen in the upper right includes a voltage regulator, three status LEDs, and one user input switch. Once triggered, the sled will move back and forth, contacting an old mouse microswitch which acts as the limiting switch. We find it entertaining that [Rohit] prototyped the circuit on a breadboard, then used that success to etch the final circuit board (shown in the video below).

If you’ve been following the hacker creed and never getting rid of any junk you’ll have no problem finding a donor drive to make one of your own. But just in case you can’t get a hold of this hardware a similar agitator can be built using a hobby servo.

Continue reading “PCB Agitator From A Broken CD-ROM Drive” →

Git With Eagle: Add Meaning to Diff

September 4, 2013 by Mike Szczys 11 Comments

a-glimpse-of-git-with-eagle We love Git. We know everyone has their favorite version tracking tools. But even those that don’t care for Git should see the value of getting meaningful Diff data from tracking Eagle layout files.

Was that last sentence just gibberish to you? Let’s take a step back. A few years ago it was impossible to use version control with Eagle at all because the schematic and PCB layout software used to save its files as binaries. But then Cadsoft transitioned to saving Eagle files as XML. This opened the door for things like scripting to rename parts en masse and to track the files under version control. One problem with the latter has been that performing a Diff on two different versions of a file results in XML changes that are probably not human readable. [Patrick Franken] wrote this script to add at least a glimmer of meaning.

We’d love to see some kind of side-by-side highlighting on the schematic or board renderings themselves. But that’s quite a ways off if we ever actually see it. For now his script will take the Diff and print out the tables seen above denoting which types of changes were made from one version to the next. It’s a start, and we hope it inspires even more work in this area.

A Pick And Place Tool From Medical Equipment

September 3, 2013 by Brian Benchoff 41 Comments

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A vacuum tool is an invaluable tool if you’re working with tiny SMD parts, and even with tweezers you might have a hard time placing these nearly invisible components on their pads for soldering. One tool that’s really great for these parts is a vacuum pen, usually made from an old aquarium air pump. [Jon] may have found a much more suitable piece of equipment to scavenge for a vacuum pen build – a nebulizer.

Nebulizers provide asthmatics with low pressure, low volume air to atomize medication for inhalation. Inside the nebulizer is a small diaphragm pump, just like the small aquarium pump teardowns we’ve seen. In just five minutes, [Jon] tore his thrift store nebulizer apart and reversed the flow of air, turning something that blows into something that sucks.

After the suction part of the build was finished, [Jon] needed a way to pick up small components. He did this by blunting a large hypodermic needle and fastening it to the end of a Bic pen with heat shrink tubing. After drilling a small hole in the pen body, he had a very nice looking SMD vacuum pump.

Making A HP Frequency Counter More Accurate

August 26, 2013 by Eric Evenchick 38 Comments

[Gerry] built his own high stability timebase add-on for his HP 53131 frequency counter. This project started out after [Gerry] built a rubidium 10 MHz standard for his lab. Upon connecting the standard to the frequency counter for calibration, he found that the HP 53131 had an awful internal oscillator. The official high stability timebase add-on from HP cost about $1000, and he was determined to do better.

Using a second hand OCXO as the oscillator, he designed his own add-on module. OCXO modules pack a crystal oscillator in a thermal chamber. Since temperature fluctuation causes drift in crystal oscillators, an OCXO controls the temperature to keep the frequency constant. They can be bought second hand on eBay for under $30.

The PCB design for the module can accommodate a variety of OCXO modules. It uses a high speed comparator and a high stability 5 volt reference to provide the clock signal to the counter. A DAC is used to calibrate the oscillator. By keeping the same DAC as the original counter, the add-on board can be calibrated using the front panel of the device.

The project is a drop in replacement for HP’s $1000 module for a fraction of the cost. [Gerry]’s write up has all the details you’ll need to build your own.

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Logging Two Multimeters At (nearly) The Same Time

August 26, 2013 by Mike Szczys 13 Comments

log-two-multimeters-at-one-time

It’s pretty common to have at least a couple of meters around to measure different values of a circuit at the same time. Where [Emilio P.G. Ficara] ran into a problem was logging the data from both at once. These ~~Fluke~~ meters have a serial-out, but his computer only has a single serial-in port. He cracked open one of the meters and figured out how to log data from both at the same time.

A lot of folks would look to a microcontroller to solve this problem. You use the chip to pull from each meter simultaneously and report back to a computer (or just dump the values onto an SD card). But this solution is a simple mechanical connector and a bit of creative programming. The way the serial output is set up on these meters they won’t interfere with each other as long as they’re read one at a time. [Emilio] wired them up as seen above, using his own software to manage the pins of the serial port. The example output he posted shows readings from the meters taken within about a tenth of second from each other. That should be good enough for most applications.