Test PCBs on a Bed of Nails

While it might be tempting to start soldering a circuit together once the design looks good on paper, experience tells us that it’s still good to test it out on a breadboard first to make sure everything works properly. That might be where the process ends for one-off projects, but for large production runs you’re going to need to test all the PCBs after they’re built, too. While you would use a breadboard for prototyping, the platform you’re going to need for quality control is called a “bed of nails“.

This project comes to us by way of [Thom] who has been doing a large production run of circuits meant to drive nixie tubes. After the each board is completed, they are laid on top of a number of pins arranged to mate to various points on the PCB. Without needing to use alligator clamps or anything else labor-intensive to test, this simple jig with all the test points built-in means that each board can be laid on the bed and tested to ensure it works properly. The test bed looks like a bed of nails as well, hence the name.

There are other ways of testing PCBs after production, too, but if your board doesn’t involve any type of processing they might be hard to implement. Nixie tubes are mostly in the “analog” realm so this test setup works well for [Thom]’s needs.

Hackaday Links: May 22, 2016

Lulzbot’s TAZ 6 has been released. Lulzbot’s printers consistently place in the top three of any 3D printing list, and the TAZ 6 will likely be no exception. [James Bruton] was one of the lucky ones who got a review unit, and first looks are promising. The TAZ 6 has the auto bed leveling found in the Lulzbot Mini, and a ‘power tower’ for all the electronics. There are completely unconfirmed rumors (or someone told me and I forgot who) that the power tower will be available separately at some point.

The most impressive circuit we’ve seen this week month year is the dis-integrated 6502. It’s a discrete 6502 CPU, about a square foot in size. It’s slow, but it works. RAM and ROM is easy to make embiggened, which means someone needs to build a dis-integrated 6522 VIA. Who’s game?

[Jeremy Cook] wanted to learn another CAD package, in this case Onshape. Onshape is the ‘first cloud-only CAD package’, which has one huge bonus – you can run it anywhere, on anything – and one huge minus – it’s in the cloud. He designed a bicycle cupholder.

Last week, several thousand Raspberry Pi Zeros shipped out to retailers in the US and UK. For a time, Pi Zeros were in stock in some online stores. Now? Not so much. Where did they all go? eBay, apparently. It’s called arbitrage, and it’s the only risk-free form of investment.

Remember those ‘bed of nails’ toys, that were basically two sheets of plastic, with hundreds of small pins able to make 3D impressions of your face and hands. No, there is no official name for these devices, but here’s a Kickstarter for a very clever application of these toys. You can use them to hold through hole parts while soldering. Brilliant.

You should not pay attention to 3D printers on Kickstarter. Repeat after me: you should not give money to 3D printers on Kickstarter. Here’s a 3D printer on Kickstarter, promising a 3D printer for $74. I own several hats, and will eat one if this ships by next year.

Remember bash.org? It’s being reimplemented on hackaday.io.

Bed of nails and accuracy in PCB manufacturing

A few days ago, we mentioned the new ARM-powered Teensy 3.0 project on Kickstarter. The creator, [Paul Stoffregen], decided to share the trials of building a test fixture along with a shocking comparison of the accuracy of different PCB manufacturers in an update to his Kickstarter.

Because [Paul]’s Teensy 3.0 has more IO pins than should be possible on such a small board, the test fixture to verify if a board is defective or not is fairly complex. To test each board, a Teensy is placed on dozens of spring-loaded contacts arranged like a bed of nails. From there, another Teensy (this time a Teensy 2.0) performs a few tests by cycling through all the pins with several patterns.

Because the spring-loaded contacts require rather precise drill holes in the PCB of his test fixture, [Paul] thought it would be neat to compare the accuracy of several board houses. In the title pic for this post (click to embiggen), [Paul] demonstrates the capabilities of OSH Park, Seeed Studio, and iTead Studio. The lesson here is probably going with a US company if quality drill work is a necessary requirement of your next project.