Voltage Logger Does It The Right Way

December 6, 2012 by Brian Benchoff 6 Comments

testing

The folks over at Adafruit have been busy designing an LED matrix wristwatch for a while now. The circuit works great, but since this watch is powered by a coin cell battery, they’d really like to get the power consumption as low as possible. This means they needed a test rig to measure the consumption of each firmware revision, but how exactly do you build a voltage logger that works with voltages and currents this small? It turned out to be a very interesting project, with plenty of info on how to build an accurate voltage logger for really small projects.

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An Inexpensive Manual Pick-and-Place Machine

November 24, 2012 by Jeremy Cook 20 Comments

When dealing with surface mount components, a manual pick-and-place machine is certainly a helpful device to have. Unfortunately, they can be quite expensive, so [Vassilis] came up with his own solution.

While commercial setups can cost upwards of a thousand dollars, this setup was made for less than a tenth of this cost. This one uses a simple setup of sliders and bearings available from a local hardware store. A cheap vacuum pen is used to lift the components, using an aquarium pump in reverse to generate suction. Finally, a USB microscope is used to make sure everything is placed in the correct position.

Plans are available on the site in DXF format, so you can build your own. The setup is reminiscent of a DIY CNC router, like this one that we featured a while ago. We could even see something like this serving a dual role with interchangeable heads for whatever you happen to be making that day!

Update: [Vassilis] published an video demonstration. See it after the break.

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Automated Resistor Sorter Puts Them Into Small Plastic Tubes

November 21, 2012 by Brian Benchoff 15 Comments

This one might be an oldie, but it’s certainly a goodie.

Way back in 2005, [David] and [Charles] needed a project for one of their engineering courses. With so many loose resistors scattered over the lab, they decided to build an automated resistor sorter (PDF warning) to separate these resistors and put resistors of the same value together in the same bin.

The electrical and programming portion of this build is relatively simple – just a PIC microcontroller reading the value of a resistor. The mechanical portion of this build is where it really shines. Resistors are sorted when they pass through small plastic tubes mounted to a wooden frame.

There are several levels of these tubes in [David] and [Charles]’ sorter that move back and forth. The process of actually sorting these resistors is a lot like going down a binary tree; at each level, the tube can go right or left with the help of a solenoid moving that level of the frame back or forth.

[David] and [Charles]’ project wasn’t entirely complete by the end of the class; to do so would require 8 levels and 128 different tubes on the bottom layer. Still, it worked as a proof of concept. We just wish there was a video of this machine in action.

Tip ‘o the hat to [Alexander] for finding this one and sending it in.

Large Area X-ray Detector

November 16, 2012 by Mike Szczys 17 Comments

This is an x-ray detector built by [Ben Krasnow]. It’s an interesting combination of parts working with an oscilloscope. The result is an audible clicking much the same as you would hear from a Geiger counter

He’s measuring backscatter, which is the reflection of x-rays on other objects. Because the signal will be quite weak compared to waves emitted directly from an x-ray source he needed a large collector to measure them. He started by gutting an x-ray image intensifying cassette. This has a phosphor layer that glows when excited by x-rays. The idea is that the glowing phosphors do a better job of exposing film than direct x-rays can. But [Ben’s] not using film. He built that pyramid-shaped collector with the phosphor material as the base. At the apex of the pyramid he mounted a photomultiplier tube (repurposed from his scanning electron microscope) which can detect the excited points on its surface. His oscilloscope monitors the PMT, then issues a voltage spike on the calibration connector which is being fed to an audio amplifier. Don’t miss his presentation embedded after the break.

[Ben] mentions that this build is in preparation for a future project. We’d love to hear what you think he’s working on. Leave your guess in the comments section.

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$4 Volt Meter From A Dollar Store Pedometer

November 12, 2012 by Brian Benchoff 37 Comments

[Paulo]’s got a few solar panels on his shed, and while he does have a fairly nice setup with a battery charge controller, he found himself looking around for a panel voltmeter. Of course you can buy a panel voltmeter for under $20, but [Paulo] wanted something that fit his 4-4-4 plan; his voltmeter should cost under $4, draw less than 4mA, and last for 4 years. The jury is still out on the 4 year qualifier, but he did manage to meet his other goals by repurposing a dollar store pedometer as a voltmeter.

The pedometer in question is a very simple device. After inspecting the PCB, [Paulo] found it operates by looking at a trigger pin and incrementing the number on the display each time the circuit closed. [Paul] designed a very small PIC12F-powered circuit that reads the voltage of his batteries and triggers the pedometer’s LCD for every 10th of a volt. To display 12.6 Volts, [Paulo]’s code triggers the LCD 126 times, for example.

After wiring up the reset button so the display will go back down to zero for each new reading, [Paulo] encased his new volt meter in a plastic box. It’s not exactly a fast way of measuring voltage, but seeing as how that won’t change very fast, it’s the perfect solution for [Paulo]’s solar charger setup.

Hands Free Hot Air Station

November 7, 2012 by Mike Szczys 13 Comments

In an effort to ease the process of soldering Ball Grid Array (BGA) chips at home [Roger] rigged up a hands-free solution for his hot air equipment.

The main component in the build is an Aoyue hot air rework station that he already had in his workshop. He wanted an adjustable mount that would hold it steady when reflowing parts so he hit Amazon and bought a $14 articulated lamp. After ditching the funnel-shaped shade he bolted a cable clamp to the socket housing. This can be tightened on the hot air wand, with the spring tension of the lamp making it easy and quick to reposition the nozzle. [Roger] sent this project directly to our tips line and we’ve embedded the rest of the project images after the break.

If you’re looking for a more DIY rework solution you should checkout this hot air pencil hack. It uses a desoldering iron, a fish pump, and some metal mesh as a heat sink to put out a stream of very hot air.

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Measuring SMD Parts With A Home Brew Version Of Smart Tweezers

November 7, 2012 by Brian Benchoff 22 Comments

SMD parts are great; they allow you to pack more parts on a board, do away with drilling dozens of PCBs, and when done correctly can produce a factory-quality board made in a home lab. There’s one problem with SMD parts; troubleshooting and measuring them. The ideal solution would be something akin to the Smart Tweezers we’ve seen before, but this fabulous tool costs three hundred bones. [Kai] came up with a much cheaper solution: home brew smart tweezers that can be built for a tenth of the cost as the professional model.

What [Kai] built is an LCR meter, basically a tool that measures inductance, capacitance, and resistance in a very, very small form factor. The technique of measuring a part’s properties involves feeding a set frequency into the device and measuring the phase, voltage and current coming out. It’s all wonderfully explained by [Dave] over at EEVblog in one of his earlier videos.

The hardware [Kai] is using includes an LCD display from a Nokia phone, an MSP430-based microcontroller, a very tiny opamp near the tip of one of the points of the tweezer, and a programmable gain amplifier used to measure the components. In testing, [Kai] can measure very low-value components with a +/- 2% accuracy, and larger, more realistic components with +/- 0.25% accuracy. An awesome accomplishment, and much better than the common Chinese meters that can’t measure in the nH/pF/mΩ range.

[Kai] hasn’t gotten his pair of smart tweezers working yet – he still needs to get the circuit up and running and write some software. We’ll keep our readers apprised of [Kai]’s progress, though, and gently convince him to work with Seeed Studio or someone similar to get his version of Smart Tweezers onto maker’s workbenches the world over.