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.

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

Voiding a warranty on an external hard drive

After a recent hard drive failure, I realized I need to start doing some proper backups (Duh, right?) Anyway, while shopping for hard drives to build a backup NAS (for which I need some internal drives, not external USB drives) I discovered a trend where a lot of external hard drives are cheaper than internal drives at the same capacity. How does this make sense?

I ended up purchasing these 3TB hard drives for about $140 each at Office Depot. It’s a crap shoot on which hard drive will be inside, but it will normally be made by the same manufacturer, and be of that capacity. (You would be surprised to find out this isn’t _always_ the case).

Being a 3TB Seagate, a quick search over at Newegg shows this drive which sells for $229. That’s a $90 dollar difference. WOW! So doing this instead of buying internal drives is a bargain so far.

Just playing around with the iPad app Animoog, which I believe is still available for $0.99 at the iTunes app store. This is a huge bargain on a really really cool app. I won’t get into the specifics of the app, but if you want to know more about what Animoog is or how to use it, I recommend this YouTube video.

So, while playing around with the Animoog app, if you go into the setup menu there is a selection under ‘Refresh MIDI input(s)’ where you can select ‘Off’ or ‘Network Session 1′. This intrigued me! Apparently you can use MIDI over the ‘Network’. After some Googling I was still unclear on how to get this setup, so I thought I’d just tell everyone how I did it so you can get to making some cool tunes yourself.