Archive for August, 2012
Of course I’m talking about gerbv! For those of you who don’t know, gerbv is a free Gerber or RS-274X viewer that comes from the gEDA Project. It’s free, it’s open source, it’s cross platform… (quick link to windows version download here) and that’s awesome.
So, why do you care? Well, if you are building your own circuits and want to get a PCB made then usually the format you’ll need to export your design into is a gerber. The reason you should grab gerbv is to double check for errors. When you design a PCB in your favorite circuit layout tool, whether it be Eagle, Altium, or my favorite DipTrace, you should double check for errors.
We’ve been having some fun decorating, painting and building new workbenches for the hackerspace. We also realized we have a lot of junk to sort through! Whew!
Anyway, if you haven’t stopped by yet, we wanted to show the progress of how things are coming a long. Here are some updated pictures:
Ideas like this would be a great way to fund a hackerspace. What other small exhibits could you build that would provide entertainment in exchange for a quarter?
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.
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.
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
|1/2 Oz.||.7 mils|
|1 Oz.||1.4 mils|
|2 Oz.||2.8 mils|
Copper Weight / Thickness Chart