Battery Capacity Tester Lifts The Veil On Manufacturer Capacity Claims

March 14, 2011 by Mike Nathan 24 Comments

battery_cap_tester

[Nick] was tasked with building a battery capacity tester by one of his teachers in order to test some aftermarket batteries that were purchased for their Vex robotics lab. The batteries were cheaper than the official version, but boasted more than twice the capacity. Fairly skeptical of the rating, he got to work designing his circuit.

He originally planned on discharging the battery through a resistor and measuring the voltage with a PIC microcontroller. After prototyping the circuit, he found that the PIC did not have enough storage space for the data he was collecting, and that there were issues with fluctuating current as the voltage decreased.

Undeterred, he built a new tester using a Teensy microcontroller and a different discharging circuit using a LM317T. This second version not only included an LCD screen to track the discharging process in real-time, but it also dumps all of the data and calculations to a spreadsheet on the computer connected to the Teensy.

The capacity tester works pretty well, according to [Nick]. He says that most batteries overestimate their capacity, and that his meter is getting readings within an acceptable variance when testing known good batteries. What about those knock-off batteries from China? He discovered that they can hold about half the charge that they claim – it’s a good thing he decided to test them out!

While he provides the software he used for the tester, there are no schematics to be found. Check out some of the other battery capacity testers we have featured in the past for tips on building one yourself.

DIY Hot Air Reflow Station

March 10, 2011 by Mike Szczys 10 Comments

Add to you bench tools by building this hot air reflow station. [Tobi] had a difficult time and was getting frustrated with the reflow oven he was building. He ditched that and set out on this project after drawing inspiration from a hot-air pencil project.

Pictured above is the business end of the device. On the right you can see the tubing that delivers air from an aquarium pump. At the center of the probe is a glass tube containing the heating element. A thermocouple is monitored by an ATmega644 to maintain the desired air temperature which can be dialed in on the base unit. This thing can put out air that’s around 500 degrees Celsius which has cause some problems with melted tubing and singed spacers. The final design includes a cover that fits over everything and hopefully provides adequate thermal isolation for the user’s hand.

[Tobi’s] base unit include faceplates for the front and back milled out of copper clad board. This really makes the tool look a bit more trustworthy. He assures us that there is a demonstration video on the way.

PC Casemod-inspired Benchtop PSU

March 9, 2011 by Mike Nathan 28 Comments

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[Will] had a cheap power supply sitting around, and decided to turn it into a full-featured benchtop PSU. Inspired by some of the other benchtop supplies we have featured in the past, he decided that he wanted his PSU to be more than just a simple-looking box sitting on his work bench. Taking some cues from PC case modding, he put together a unit that is not only very useful, but also quite sharp looking.

The frame of the case was crafted from aluminum angle, while all of the other flat surfaces were made using black polycarbonate. He installed the standard 12v, 3.3v, and 5v terminals you would expect from any benchtop PSU, complete with an LCD display showing the voltages provided by each rail as measured by an Arduino stationed inside the case. Additionally, he installed a variable terminal capable of providing 1.3v-30v, along with its own LCD display. The most unique feature is the multimeter embedded in the front of the case, which makes it virtually impossible to lose.

The case is finished off as you might expect, if you have seen any of his previous work. It features LED lighting on the inside, large fans on either side of the case for optimal air flow, and a pair of machined aluminum handles.

Be sure to check out the quick video below of the PSU being powered on.

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Arduino Thermo-cam

March 9, 2011 by Kevin Dady 31 Comments

[Maxbot] wanted a inferared themo-cam that he could use to scan an area and display the results on his computer, the result is this Cheap-Thermocam. This little device is a inexpensive thermal sensor mounted on a pair of servo’s for XY scanning, custom java software and an Arudino to mate the two.

The sanner does a limited but still useful resolution of 42×32 pixels. To help out with smoothness of the colors, every other line of the finished product is interpolated against its neighbors. It takes the device about two minutes to measure each of the 1344 points, but what it lacks in speed it more than makes up for in cost, boasting around 100$ build cost, and ease of construction.

While exact details of what parts you need and how to hook everything up is lacking at this moment, there is a page in the works that will let you know all the good details “soon”, though if you are inspired to replicate one of these nifty devices it seems the most difficult part would be tapping into the sensor’s electronics and the custom software.

Cheap, hacky, and even comes with its own roll of duct tape. We have a short video for you after the break.

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Hacking Strippers To Do Your Bidding

March 3, 2011 by Mike Nathan 38 Comments

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[Alex] knows his strippers.

By his estimation, he has stripped millions of wires over the years, and he has seen his fair share of wire strippers come and go. That cheap set of wire strippers you have with the graduated holes, or that adjustable stripper you squeeze as you pull the wire through? They just stress the insulation as well as the wires you are trying to strip – he says you might as well just use them in your tackle box.

His favorite style of wire stripper is the automatic kind that grip the wire, then cut and remove the insulation just by squeezing the handles. His issue with this particular tool is that it’s difficult to get a uniform length of stripped wire when working in volume.

Since [Alex] needs uniformity in his line of work, he modified a set of automatic wire strippers to include an adjustable wire stop. He determines the length of wire he needs, adds or removes some washers from his wire stop, and off he goes. It’s a very simple yet very useful hack, depending on your application. We bet it is probably one of the most accurate ways to get uniform length, this side of a fully automatic wire stripper.

Simple PCB Etchant Made From Chemicals You Can Put In Your Mouth

March 3, 2011 by Mike Nathan 68 Comments

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[Stephen] often finds the need to make his own PCBs at home, and when he got the urge to do some etching recently, he realized that he was fresh out of “Ferret Chloride and Bureaucratic Acid*.” Undeterred by his empty chemical cabinet, he poked around in his kitchen mixing together anything and everything that might have the ability to strip copper from a PCB.

Now, we don’t necessarily recommend this course of action, but it seems that he finally hit upon a winner. He discovered a formula that can be made at home from simple and safe household ingredients which does the job quite nicely. A fair warning however, standard ferric chloride disposal procedures need to be followed when using this solution.

If you want to know what he concocted in his kitchen as well as the chemistry behind it, you will have to visit his site, we won’t ruin it for you. You can however, see the solution at work in the video we have posted below.

*His joke, not ours

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Open Source Laser Cutter (v2)

March 2, 2011 by Kevin Dady 23 Comments

The Buildlog.net 2.x Laser is a second generation open source laser cutter that definitely improves the design of the first model. The 2 axis machine (optional vertical axis is manual or an upgrade is available) boasts a large 12” x 20” x 4” workspace while being smaller than its predecessor, fitting a table top design.

The older model had a goal of being self replicating, which limited the types of materials used, the new 2.x model drops that goal and uses stronger metal parts. Electronics are now modularized that allow easier and cleaner wiring, though you will still need a controller board.

There is an XMOS based controller provided on the main page of BuildLog.net, along with mechanical drawings, schematics, gerbers, instructions for both machines, and kit parts (for the first model) along with resources for the heavy items like laser tubes and power supplies.