Monthly Archives: May 2016

ViaConnect circuit board test tool

via Dangerous Prototypes


David Spinden writes, “Wanted to pass along an open source hardware circuit board tool that allows a person that has a circuit board that has vias for .1 inch headers, but has no headers to prototype for their idea. Using a spring contact, the ViaConnect attaches directly to the via. It is great for students who can’t solder, hobbiest who don’t want to solder the headers,or professionals who want to try something in the lab, factory or field. The instructions include parts that can be bought at Digikey and Amazon.”

Project info at

Via the contact form.

Check out the video after the break.

La Skala Arduino controlled ladder attenuator

via Dangerous Prototypes


Dimdim has designed and built his own stepped ladder attenuator, controlled by an Arduino:

A few years ago I had an encounter with a ladder volume attenuator. I loved hearing the relays clicking away as they dialed-in the desired attenuation.
Ever since then I wanted to design and build one for myself. The years passed, with other more urgent projects taking priority, but I always had this thing stuck in the back of my mind. I was doing my research at a very slow rate. Slow, but steady. I came across a number of ready-made ladder attenuators, such as the RelaiXed2, the one from AMB, Vicol, and others. I also came across some uC source code, but nothing ready-made for an Arduino.

Project info at Dimdim’s blog.

Maker installs an Android tablet in his car’s dashboard

via Arduino Blog

Unlike many cars today, Aykut Celik’s 2014 Volkswagen Polo didn’t have Bluetooth connectivity or an elaborate touchscreen navigation system. So, the Maker decided to take matters into his own hands and swapped out his “useless” radio for a Samsung tablet, putting Google Maps, Spotify and other apps right in his vehicle’s dashboard.

In order to accomplish this, Celik needed an amplifier (to replace the one attached to the prior radio), a CAN bus shield from Seeed (so he could use the steering wheel’s volume buttons), a Bluetooth module, and an Arduino Mega 2560 (for parsing data and sending it over to the Android device).

A CAN-BUS shield is necessary to be able to read CAN-BUS commands from the CAN bus line… I used this shield for detecting wheel button commands like volume up, mute and volume down. Behind the car radio there are two CAN bus cables. One of them is CAN bus – HIGH and the other is CAN bus – LOW. These cables must be connected to green sockets on the shield.

Using the SeeedCAN bus shield, you can sniff you car’s CAN bus data.

The info which is gathered from CAN bus is transferred to the Android tablet via Bluetooth. There is a little app which is responsible, for example, reducing volume whenever the wheel volume button is clicked. And a menu activity to open other apps.

You can watch the elaborate project below, and read more about it on Celik’s blog. The Maker has also made the software and other information available on GitHub.

Building a Wireless Kill Switch

via SparkFun Electronics Blog Posts

I highly recommend building something that scares you every once and a while. In this case, I’m planning to enter an autonomous vehicle into the AVC in 2016, and it’s pushing my limits of comfort. A 1,000W motor with a large battery pack behind it means that if things go wrong, they go really wrong!

alt text

The innards of the remote kill switch

For that reason, one of the new safety requirements of the AVC rules is a remote kill switch that allows the user to safely and remotely power down the vehicle. So here’s a tutorial going into how I built the wireless kill switch based on the RFM69. And to demonstrate this… well… let’s start with a margarita.

Vehicle Control Unit Electronics

Checkout the kill switch tutorial for the complete rundown!


How to Build a Remote Kill Switch

May 31, 2016

Learn how to build a wireless controller to kill power when things go... sentient.

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How to measure laser cut length or time?

via Dangerous Prototypes


To price laser cutting online we need to extract two pieces of info from uploaded design files. The area of a box surrounding the design, called the bounding box, is the amount of material needed. The length of all the cuts in the design can be used as a rough estimate of the cutting time consumed. Here’s where we’re at…

A dirty cheap laser cut service has been “coming very soon” for far too long. We planned to take SVG files and use a friend’s script to measure the bounding box and cut lengths. Unfortunately we never found a laser cut supplier willing to take low volume/high-mix orders and provide all the pricing info to give instant quotes.

Last week a comment at Hack a Day mentioned that dirty laser cutting is taking forever. Surprised by the interest, we asked around and found some willing suppliers. However, these suppliers only accept dxf, dwg, pdf, eps, and ps formats. SVG won’t do. Now we have a supplier but no way to give instant online quotes.


Converting to and from SVG is plagued with wrecked arcs and curves. Potential customer dissatisfaction factor is super high. Absolutely not reliable enough for a commercial service or even for pricing.

Extracting info from CAD programs

Inkscape loads all the above formats, but we were not able to extract total path length from the command line or the shell interface. is an online version of AutoCAD that might be able to provide the design stats and a nice rendering, but if the API is slow or busy are customers supposed to wait minutes for their quotes?

A couple CAD programs seemed promising, but eventually we couldn’t find anything that runs on Linux and can extract the stats we need via the command line.

Measuring scripts

The script that measures PCBs in our store and at DirtyPCBs combines a bit of gerber code knowledge with some math to crank out basic stats without ever loading a CAD program. A small script to extract path length and bounding box size from dxf is very doable after a quick thumb through the spec, however nothing seems to exist online.

The learning curve to implement the dxf format and the debug time to perfect it puts this in the labor of love category. It would be a blast if we really wanted to do it, but since it’s standing in the way of a dirt cheap service that will likely never turn a profit (laser cutting is cheap and common…) there’s no resources to dedicate to writing our own.

Create g-code and simulate the cut

G-code is a popular way to control CNC mills and 3D printers. A CAM processor (yes, like the one in Cadsoft Eagle) combines information about the machine, such as cut speed, with the path in the design file to create a series of cutting steps or instructions. G-code is accepted universally, much like gerber files.

Lots of existing scripts convert dxf/pdf/eps/ps files to g-code. Once the design is in g-code there are several programs that simulate the cut and estimate the cut time (or filament used, etc). This seems like the proper way to do it. As a bonus, it lays the framework to calculate cut time and difficulty for a future DirtyCNC and DirtyInjectionMolding service.

This is as far as we’ve gotten. A dozen Python scripts on github look promising, but nothing directly outputs the info we need without a bit of hacking. We’ll continue to knock together a solution in the next few days.

Please shout out in the comments if you have thoughts on any of these methods or experience with any tool chains that might work. Help us get laser cutting online and we’ll reward you with – what else – free laser cutting service!

Image source: Adam Dingley CC BY SA

Home automation with Make: and OpenHAB

via Raspberry Pi

The good folks at Make: have been working with open-source home automation software OpenHAB to make a touch-screen device to interact with your house.

home automation led control

OpenHAB allows you to control objects in your house with voice commands; to monitor sensor networks; to set up rules for your devices via email or IFTTT, and a whole lot more. The device this video shows you how to build can interact with up to 150 different smart home products, and provide an interface for control and task scheduling.

For this project, you’ll be building your own array of neopixels (which are great for kitchen counter lighting and for adding some mood colour to lighting schemes, if you’re looking for an excuse to get started) rather than interfacing with a pre-built device, so you can get right into the guts of what’s going on here. Other devices are easy to add once you’ve got the base model built. Here’s Jordan Bunker to get you started.

Weekend Project: Home Automation with Raspberry Pi and OpenHab

Using the open source software OpenHAB, we’ll be building a Raspberry Pi touchscreen command center that can interface with over 150 different “smart home” products, and provide an interface for control and task scheduling. Read more about this project: Arrow Electronics: Music:…

You can read more about this project over at Make:, where there’s a step-by-step guide with photos to accompany the video.



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