Hackaday Links: July 13, 2012

Testing LEDs

Over at the Albuquerque, NM hackerspace Quelab, [Alfred] needed to test a bunch of surface mount LEDs. He ended up building a pair of 3D printed tweezers with a pair of needles attached to the end and a space for a coin cell battery. It works and Quelab got a new tool.

Woo Raspberry Pi

[tech2077] added an FTDI chip to his Raspberry Pi to do a little single cable development. We’ve seen a few similar builds, but surprisingly nothing related to the on board display serial interface. This wiki page suggests it’s possible to connect an iPhone 3G or iPhone 4 display directly to the Raspi. Does anyone want to try that out?  Nevermind, but it would be cool to get a picture from a display plugged into that display port on the Raspi.

I like to ride my bicycle, I like to ride my bike

Over at the 23b hackerspace a few people were having trouble finding a good bike cargo rack that wasn’t overpriced. They built their own with $30 in materials and a salvaged milk crate. It looks great and is most likely a lot more durable than the Walmart model.

If that cargo rack fell off, it would look like this

Apparently you can get ‘spark cartridges’ to attach to the underside of a skateboard. [Jim] saw these would look really cool attached to his bike so he did the next best thing. He attached them to his sandals. It does look cool…

Less heat, less noise

[YO2LDK] picked up a TV tuner dongle for software radio and found it overheated and stopped working after about 15 minutes (Romanian, Google Translate). He hacked up a heat sink from an old video card to solve this problem. Bonus: the noise was reduced by a few tenths of a dB.

LiPo battery tester for solar vehicle battery array

If you’re building solar vehicles at a competitive level you’ve got to know exactly how the storage batteries will perform. To that end [Matthew] built a Lithium Polymer battery tester for use by the McMaster University Solar Car Project. It worked well, but could only test one battery at a time. He just finished up a second version, which can test battery specifications on up to eight units at once. It saves a lot of time, but still takes fifteen hours to test just one set of the units used by the vehicle.

The most important aspect being measured is the discharge curve. Sure, there’s a datasheet that includes this information, but how can be sure that what you received will perform at spec? Each of the eight channels can be disconnected from the system using a relay. This is just one of the safety features which watch for things like over-voltage and over-current conditions. Remember, Lithium batteries can heat up fast if there’s a problem. Data is sampled on a 12-bit ADC and can be pushed to a computer via USB for graphing.

Full-featured battery tester puts them through their paces

When working on battery-dependent projects you want accurate performance information where a datasheet may not be available. [E. Lelic] set out to build a device that would meter internal battery resistance but ended up with a bench tool that can do much more than that.

A PIC 16F88 microcontroller takes center stage on the meter, taking voltage level readings, monitoring a DS1820 temperature sensor, and controlling an LM2575 step-down regulator. The components provide functionality for measuring Lithium Ion, Lithium Polymer, Nickel Cadmium, Nickel Metal Hydride, and Alkaline batteries. It is capable of fully discharging and fully charging the batteries, measuring time and power consumption during this cycle, and monitoring temperature changes for the NiMH and NiCad versions.

Look for the little red ‘Download’ icon at the bottom of the post linked above. That archive includes a schematic (which we’ve also embedded after the break), board layout in .LAY format, and a HEX firmware file.

If you enjoyed this build you might want to look at this other battery capacity tester.

[Read more...]

Unique Li-Ion battery tester


[moris_zen] found himself with a hand full of Li-Ion batteries and no good way to see what their capacities were. He built a this unique tester really quick to get the job done. He’s using off the shelf components and a cheap pocket watch which he bought in Taiwan for $1. You hook the circuit up to your battery, click the button and the watch starts working. When it stops, you multiply that number by .38 to get your amp/hour results. Sure, he could have just used a counter, but this is an interesting approach. All he needs to do now is make a nice container to hide all of the circuitry. How could he change the circuit to make the end multiplication unnecessary?