Power over ethernet, sorta

So we’re still busy decking out the new facility and one of the things we wanted to get up and running is some cheap surplus ethernet cameras to … keep an eye on things and check out whats going on remotely. So I thought I’d go ahead and set these guys up.

First thing up was to make some cat5 cables. I got a cheapo crimper, cable tester, and connectors off eBay. While trying to figure out how much cable I need to run I was thinking about how I’m going to plug the cameras in to supply power. They have wall warts with barrel jacks running 12 volts. I started thinking about how power over ethernet works and thought I’d try to see how I can do the same thing to run the power to the camera. These aren’t POE cameras so the idea was to only half crimp the connectors, and use the unused pairs to run the 12 volts.

Here is the layout of how cat 5 cables should be done. Credits to wikipedia.

So there are 2 color coded standards for crimping cables, but oddly enough, the ones we care about are blue, blue/white, white/brown, and brown. Pins 4, 5, 7, 8. These pins aren’t used in 10/100 connections, however if it was gigabit then they would be used. So the unused pins are the same on both standards, so I just chose the first one.

Roly Kit – Amazing Retro Storage for Makers

The Roly Kit storage box. I vaguely remember seeing these things from my childhood, sometime in the 80’s, but that was a long time ago. I think I had totally abolished these things from memory…until a year or two ago, when one of our members brought one to hack night filled with lots and lots of electronic components. We’ve all used the tiny drawers for parts storage, like the ones on our workbenches. I even have a more modular one that has a handle to carry it around, but nothing compares to the storage capacity of the Roly Kit.

After admiring the sleek rolling storage for so long, I finally decided that I had to have one. Doing a little research, it appears these things were invented sometime in the 70s, and made by a company in the Netherlands. Sadly, the only reliable place I’ve seen them for sale is eBay, and occasionally a thrift shop. They appear to come in a few colors and 2 different sizes (‘big’ and ‘medium’). If you’re a maker and need a nice travel friendly holder for all your resistors / caps / knobs / switches / 555 timers, I recommend you snag one up too.

PCB Copper Weight / Thickness Chart

The copper layer thickness in a printed circuit board (PCB) is rated in ounces (also called the copper weight) or in mils (also called the copper thickness.) Both units of measurement are relaying the same information just in a slightly different format. For example, 1 oz. of copper is equivalent to 1 square foot of 1.4 mils (.0014″) thick copper.

Copper weight/thickness is important in several areas of PCB design. The thickness and width of a trace determines the amount of current (amps) the trace can carry. The thickness is also used in the calculation of trace impedance (ohms) in RF and high speed digital circuits.

The following is the formula for cpw (in oz) to thickness (in mils) conversion:

Thickness(in oz) = thickness (in mils) /1.37

The following is the formula for thickness (in mils) to cpw (in oz) conversion:

t ( in mils) = t ( in oz) * 1.37

Weight	Thickness
1/2 Oz.	.7 mils
1 Oz.	1.4 mils
2 Oz.	2.8 mils

Copper Weight / Thickness Chart

New Hackerspace facility in Baltimore, MD

We recently moved into a 1250 square foot facility and are in the process of renovating it to suit our needs. The space is located at:

6410 Landay Ave
Baltimore, MD 21237

The floors were looking pretty bad when we moved in, so we gave them a vigorous cleansing using a floor buffer and a power washer. The floors still were not up to par, so we painted the floors using acrylic floor paint and then added paint flakes to really kick it up a notch.

Painting Floors at Baltimore Hackerspace

We need a place to work, so we built a few work benches. 40 2×4’s, 2 sheets of plywood and 2 sheets of laminate was just the right amount of wood to build 6 benches which are 32″ high x 30″ deep x 48″ long.

As you can see in the background, we have also moved much of our stuff into the space. That’s not all…We have really been hard at work in making this space feel like a warm and welcoming place to hang out and learn new skills. Paul King gave the place a slightly more social feel by adding a little graffiti to the newly renovated office wall.

Maybe that should be E=I*R but does it really matter? Google ‘Ohms Law Chart’ and you mostly find V=I*R as examples. Besides, it’s only paint so we can fix that! We plan to add a lot more electronics-related graffiti to the wall. I bet that Ohms law triangle will get used more often that people think…

RedBull Creation 2012 – Telepresence Zen Garden

For this year’s RedBull Creation competition, we had to incorporate a ‘Bullduino’ into the project of our choice. What is a Bullduino? It’s essentially an Arduino Uno shaped like the RedBull logo. So, we came up with the idea of creating a Telepresence Zen Garden. Sounds simple right? Well, it was actually more difficult than it sounds.

The diagram below shows you from a high level what we did. We created a user interface in Flash which allows the user to draw lines on a canvas. That data is uploaded to a web server and stored into a MySQL database. There is a queuing system written in PHP on the web server. The queuing system keeps track of the order in which the drawings are submitted and it is responsible for keeping the buffer full on the Bullduino. The connection between the web server and the Bullduino is a TCP socket which is forwarded to the USB-to-Serial connection on the Bullduino.

The linux laptop is running 2 things. It’s running socat which does the TCP to Serial forwarding and the Flash media encoder which streams a video feed back to justin.tv.

The Bullduino is connected to a rail of power mosfets to control turning on and off 8 banks of Red and Blue LEDs. It is also connected to 2 stepper motor drivers, 2 servos, and 4 limit switches. The limit switches are used to zero out the XY table and prevent damage to the machine should something go wrong.

One of the servos is responsible for raising and lowering the drawing pen. The other is responsible for raising and lowering the eraser bar. Here is a little video showing how the eraser bar works.

The entire system is powered by a modified ATX power supply which provides 12V for the stepper motors and 5V for everything else. The construction of the Zen Garden was a combination of hand cut MDF, laser cut wood and 3D printed brackets and pulleys.

Finding the right sand was critical. A very fine grain sand provided the best detail. We settled on using 20lbs of Nature’s Ocean Premium White Sand from Petco. We experimented with different grain sizes and even mixed the smallest grain size with the larger grain sizes but this did not provide the detailed land and peaks that the Nature’s Ocean sand provided.