Homemade Test Jig Is Cheaper Than Outsourcing

In the past, [Sjaak] has had his testing and programming jigs made for him in Shenzhen, but realized they weren’t that great of a value. They weren’t terribly expensive in the grand scheme of things, but they didn’t include any wiring, so he was still spending his own time and money. His quest to develop his own in-house jigs not only netted him a considerable cost savings in the end, but also produced a nicely detailed post on his site for anyone else who may be heading down the same path. That’s a win-win in our book.

The idea behind a jig is pretty simple: essentially it’s just a mount that holds the PCB, and a set of pins which contact the appropriate points on the board. The jig can then provide power, programming, status LEDs for testing, etc. Basically anything that you can’t or don’t want to include on the final board, but will help in testing or programming them.

To start, [Sjaak] begins with a blank PCB in Eagle and imports his target board. With the two lined up, he can then mark where he wants the pins to go on the jig, and add labels to the silkscreen to make things a little easier during diagnostics. The target board is then removed, the file converted to Gerber, and it’s sent off for manufacturing. With a few more tweaks, the file is then exported to DXF and laser cut out of acrylic. When the PCBs come back, it’s just a matter of sandwiching it all together with some standoffs and adding the pins.

[Sjaak] mentions that he was inspired by an old post on how SparkFun was internally handling their test jigs, though we think with a dash of automation he could make things even easier for himself.

The Gerber Behind Gerber Files

When we create a printed circuit board, the chances are these days that we’ll export it through our CAD package’s CAM tool, and send the resulting files to an inexpensive PCB fabrication house. A marvel of the modern age, bringing together computerised manufacturing, the Internet, and globalised trade to do something that would have been impossible only a few years ago without significant expenditure.

Those files we send off to China or wherever our boards are produced are called Gerber files. It’s a word that has become part of the currency of our art, “I’ll send them the Gerbers” trips off the tongue without our considering the word’s origin.

This morning we’re indebted to [drudrudru] for sending us a link to an EDN article that lifts the lid on who Gerber files are named for. [H. Joseph Gerber] was a prolific inventor whose work laid the ground for the CNC machines that provide us as hackers and makers with so many of the tools we take for granted. Just think: without his work we might not have our CNC routers, 3D printers, vinyl cutters and much more, and as for PCBs, we’d still be fiddling about with crêpe paper tape and acetate.

An Austrian Holocaust survivor who escaped to the USA in 1940, [Gerber] began his business with an elastic variable scale for performing numerical conversions that he patented while still an engineering student. The story goes that he used the elastic cord from his pyjamas to create the prototype. This was followed by an ever-more-sophisticated range of drafting, plotting, and digitizing tools, which led naturally into the then-emerging CNC field. It is probably safe to say that in the succeeding decades there has not been an area of manufacturing that has not been touched by his work.

So take a look at the article, read [Gerber]’s company history page, his Wikipedia page, raise a toast to the memory of a great engineer, and never, ever, spell “Gerber file” with a lower-case G.

Solder Stencils with a 3D Printer

If you are soldering with paste, a stencil makes life a lot easier. Sure, you can apply paste by hand with a syringe, but a modern PCB might have hundreds or even thousands of pads. Like a lot of us, [Robert Kirberich] doesn’t like paying to have stencils made and he wondered if he could use his 3D printer to make stencils. He found the answer was yes.

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Circuit Plotting With An HP Plotter

Over the last few years we’ve seen a few commercial products that aim to put an entire PCB fab line on a desktop. As audacious as that sounds, there were a few booths showing off just that at CES last week, with one getting a $50k check from some blog. [Connor] and [Feiran] decided to do the hacker version of a PCB printer: an old HP plotter converted to modern hardware with a web interface with a conductive ink pen.

The plotter in question is a 1983 HP HIPLOT DMP-29 that was, like all old HP gear, a masterpiece of science and engineering. These electronics were discarded (preserved may be a better word) and replaced with modern hardware. The old servo motors ran at about 1.5A each, and a standard H-Bridge chip and beefy lab power supply these motors were the only part of the original plotter that were reused. For accurate positioning, a few 10-turn pots were duct taped to the motor shafts and fed into the ATMega1284p used for controlling the whole thing.

One of the more interesting aspects of the build is the web interface. This is a small JavaScript app that is capable of drawing lines on the X and Y axes and sends the resulting coordinates from a server to the printer. It’s very cool, but not as cool as the [Connor] and [Feiran]’s end goal: using existing Gerber files to draw some traces. They’re successfully parsing Gerber files, throwing out all the superfluous commands (drills, etc), and plotting them in conductive ink.

The final iteration of hardware wasn’t exactly what [Connor] and [Feiran] had in mind, but that’s mostly an issue with the terrible conductivity of the conductive ink. They’ve tried to fix this by running the pen over each line five times, but that introduces some backlash. This is the final project for an electrical engineering class, so we’re going to say that’s alright.

Video below.

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Recreate a PCB with a Scanner and Inkscape

turnsig

[John] has managed to replace a broken turn signal PCB by scanning it and converting to Gerber format. [John] purchased a Triumph Spitfire with toggle switch wired up for turn signal control. The “official” replacement part worked better than the toggle switch, but it didn’t cancel after turning. He was able to get the original switch, only to find it had a hole completely burned through the phenolic board. This isn’t completely surprising, as Triumph used a Lucas Industries electrical system. As anyone who has owned a car with a Lucas “prince of darkness” electrical system will tell you, Lucas systems were not known for quality. A quick Google search brings up plenty of pages attesting to this.

Phenolic resin/paper was a common early PCB material.  The FR-4 fiberglass boards most commonly used today could be considered descendants of FR-1 and FR-2 phenolic. (The FR in this case stands for Fiber Reinforced). The standardization worked in [John’s] favor, as his burned board was 31 mils thick, which is still a standard PCB thickness. Re-creating an odd sized board such as this isn’t a hard job. It would however mean spending quite a bit of time with a ruler and a caliper. Rather than spend all that time measuring and re-drawing, [John] scanned his PCB on a flatbed scanner. He used graph paper as a background to verify the image wasn’t being stretched or skewed.

[John] brought his scan into inkscape, and traced both the outline and copper areas. The outline and copper had to be exported as two separate files, so he added corner marks outside the board outline as fiducials.  He then used pstoedit to convert inkscape’s eps output files to gEDA pcb format. The two files were rejoined in gEDA. From there [John] exported a Gerber, and ran it on his home PCB milling machine.  The results look good. [John] plans to make another revision of the board from a professional PCB house with vias to hold the copper to the substrate.

DIY Pick and Place just getting under way

diy-pick-and-place

It’s not totally fair to say that this project is just getting under way. But the truth is it neither picks nor places so there’s a long road still to travel. But we’re impressed with the demonstrations of what [Daniel Amesberger] has achieved thus far. Using the simplest of CNC mills he’s finished the frame and gantry for the device. You can see some of the parts on the left after going though an anodizing process that leaves them with that slick black finish.

The demo video shows off the device by driving it with a joystick. It’s fast, which gives us hope that this will rival some of the low-end commercial pick and place machines. He’s already been working on the software, which runs on a mini ITX form factor computer. This includes a gerber file interpreter and some computer vision for a visual check on part placement. He hasn’t gotten around to building the parts feeders but we’ll keep you updated as we hear back from him.

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Visualizing PCB revisions using a Gerber viewer

gerber_schematic_highlighting

We all know that Eagle has its share of shortcomings. Instructables user [westfw] was particularly annoyed by the fact that while Eagle keeps copies of up to 10 revisions of your board, it cannot open those files without resorting to manually renaming each one. Even more frustrating to him is the fact that you can’t use Eagle to view two files simultaneously in order to compare layouts. This made hunting down changes quite tedious, so he started looking for a better way to do things.

While using his favorite open-source gerber viewer gerbv, he noticed that the application let him load multiple copies of the same layer, XORing the PCBs’ colors together. Realizing that with some clever color selection, he could use gerbv to automatically highlight layout differences, he set off to automate the process.

The resulting script works on any flavor of *nix, and should play nice in Windows under cygwin as well. The script reads through Eagle backup files, renaming them and tweaking the colors so that when XORed, they show up as bright red areas in gerbv. It’s a simple yet handy tool to have on hand if you happen to do a lot of PCB design.