Endurance Test Machine Is Not Quite Useless

It seems [Pete Prodoehl] was working on a project that involved counting baseballs as they fell out of a chute, with the counting part being sensed by a long lever microswitch. Now we all know there are a number of different ways in which one can do this using all kinds of fancy sensors. But for [Pete], we guess the microswitch was what floated his boat — likely because it was cheap, easily available and replaceable, and reliable. Well, the reliable part he wasn’t very sure about, so he built a (not quite) Useless Machine that would conduct an endurance test on the specific switch brand and type he was using. But mostly, it seemed like an excuse to do some CAD design, 3D printing, wood work and other hacker stuff.

The switches he’s testing appear to be cheap knock-off’s of a well known brand. Running them through the torture test on his Useless Machine, he found that the lever got deformed after a while, and would stop missing the actuator arms of his endurance tester completely. In some other samples, he found that the switches would die, electrically, after just a few thousand operations. The test results appear to have justified building the Useless Machine. In any case, even when using original switches, quite often it does help to perform tests to verify their suitability to your specific application.

Ideally, these microswitches ought to have been compliant to the IEC 61058 series of standards. When switches encounter real world loads running off utility supply, their electrical endurance is de-rated depending on many factors. The standard defines many different kinds electro-mechanical test parameters such as the speed of actuation, the number of operations per minute and on-off timing. Actual operating conditions are simulated using various types of electrical loads such as purely resistive, filament lamp loads (non-linear resistance), capacitive loads or inductive loads. There’s also a test involving a locked rotor condition. Under some of the most severe kinds of electrical loads, a switch may be expected to last just a few hundred operations. But if the switch is used for low power applications (contact current below 20 mA), then it is expected to last up to its mechanical endurance limit. For most microswitches, this is usually in the range to 100,000 to 300,000 operations.

Coming back to his project, his first version was cobbled together as a quick hack. A 3D-printed lever was attached to a motor fixed on a 3D-printed mount. The switch was wired to an Arduino input, and a four-digit display showed the number of counts. On his next attempt, he replaced the single lever with a set of three, and in yet another version, he changed the lever design by adding small ball bearings at the end of the actuator arms so they rolled smoothly over the microswitch lever. The final version isn’t anywhere close to a machine that would be used to test these kind of switches in a Compliance Test Laboratory, but for his purpose, we guess it meets the bar.

For those interested, here is a great resource on everything you need to know about Switch Basics. And check out the Useless Machine in action in the video below.

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Another Electric Longboard Goes the Distance

Looks like electric longboards are becoming a thing, with increasingly complex electronics going into them to squeeze as much performance as possible out of them. When an electric longboard lasts for 35 miles, can longboard hypermiling be far behind?

If endurance longboarding sounds familiar, it’s because we just covered a 25-mile electric that outlasted its rider. To get the extra 10 miles, [Andrew] cheated a little, with a backpack full of extra batteries powering his modified Boosted Board, a commercially available electric longboard. But the backpack battery was only a prototype, and now [Andrew] is well on his way to moving those batteries to a custom underslung enclosure on his new “Voyager” board. Eschewing balancing and monitoring circuitry in favor of getting as many batteries on board as possible, [Andrew] managed sixty 18650s in a 10S6P configuration for 37 volts at 21 Ah. He didn’t scrimp on tools, though – a commercial terminal welder connects all the battery contacts. We really like the overall fit and finish and the attention to detail; an O-ring seal on the 3D-printed enclosure is a smart choice.

Voyager isn’t quite roadworthy yet, so we hope we’ll get an update and perhaps a video when [Andrew] goes for another record.

Flash Memory Endurance Testing

[Gene] has a project that writes a lot of settings to a PIC microcontroller’s Flash memory. Flash has limited read/erase cycles, and although the obvious problem can be mitigated with error correction codes, it’s a good idea to figure out how Flash fails before picking a certain ECC. This now became a problem of banging on PICs until they puked, and mapping out the failure pattern of the Flash memory in these chips.

The chip on the chopping block for this experiment was a PIC32MX150, with 128K of NOR Flash and 3K of extra Flash for a bootloader. There’s hardware support for erasing all the Flash, erasing one page, programming one row, and programming one word. Because [Gene] expected one bit to work after it had failed and vice versa, the testing protocol used RAM buffers to compare the last state and new state for each bit tested in the Flash. 2K of RAM was tested at a time, with a total of 16K of Flash testable. The code basically cycles through a loop that erases all the pages (should set all bits to ‘1’), read the pages to check if all bits were ‘1’, writes ‘0’ to all pages, and reads pages to check if all bits were ‘0’. The output of the test was a 4.6 GB text file that looked something like this:
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Cell Phone Endurance Tests


Gone are the days when a phone would last you a lifetime and enter the days of glass covered mobile phones built to be sexy and sophisticated. With these new phones come new testing methods. Companies like Nokia are still dedicated to making the best phones possible and making them durable through vigorous testing. The example shown in the article, is simulating a phone dropping from a shirt pocket onto the floor. Nokia claims to use 200 endurance tests encompassing temperature, extreme usage (use this button pusher for you own test), physical drops, and exposure to humidity on each new model in their product line. Makes one wonder what other companies are using for their endurance tests. There’s video of the Nokia N8 Drop Test is after the break, and don’t forget to leave a comment if you know about other interesting test methods.

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