Year: 2008

120Vac Interface for Current Measurement

WARNING: The following project deals with mains voltage, which can cause serious injury or death. Should you choose to replicate any part of this project I am not responsible for any damage, injury or death that may result.

I wanted a way to easily and safely (or semi-safely) use my multimeter’s current measuring function (ammeter) on 120Vac devices.

To measure current with an ammeter you need to break the circuit and insert the ammeter so that the electricity flows through the ammeter on its way to the device being powered.

To do this easily and safely with devices powered via mains voltage (120Vac) I made this “interface.” One side of the circuit goes directly to the outlet, and the other is broken and goes to a terminal strip. An ammeter is connected to the terminal strip, completing the circuit and allowing the ammeter to measure the current being drawn from the device plugged into the outlet.

This was easy, took only about an hour to make, and all the parts can be picked up from any decent hardware store:

I started with a standard plastic surface mount switch/outlet box:

I used small angle brackets to attach the terminal strip to the box:

Drilled holes in the box to mount the terminal strip:

Cut some machine screws down to size:

The terminal strip attached to the box:

Drilled a hole for the wires to pass through to the terminal strip:

Wired up the outlet – this is wired the same way you’d normally wire an outlet except that one side (positive in this case) of the circuit is being broken by the terminal strip:

All together:

Only the last two terminals are used, the rest are just extra:

Measuring the current draw of a desk lamp (CLF bulb). Notice that I used longer screws on the terminal strip to allow alligator clips to be clipped on:

Now I can measure the current draw of a 120Vac device (or devices) easily and relatively safely using my multimeter. I say “relatively safely” because the terminals are exposed so caution should be taken when in use. Also, it should only be used for quick measurements, noting long term.

By measuring the current draw (amps) of a device you can easily figure out how many watts it’s pulling by multiplying the source voltage by the amps.

volts x amps = watts

My CFL bulb is drawing 0.12 amps, times that by 120 and we get 14.4 watts.

Dear Curves: respect your client and employee data

The subject of this post is a US based Curves Health Club and has nothing to do with the plus size clothing company Dearcurves (

After (finally) speaking with the owner I believe that the Curves in question now takes this matter of data security very seriously and that a similar situation will likely not take place. I believe that this was an isolated oversight and that the owners have learned a valuable lesson (i.e. they were scared shitless and will probably be more careful from now on).

I should clear some things up:

  • Before publishing this I did attempt to contact the Curves in question. My phone call went un-returned.
  • Beyond the phone numbers and addresses contained in the letters (WordPerfect docs) there was no other data found on the system.
  • The Curves database was encrypted and NO EFFORT was made to circumvent this encryption; no billing information (if any existed) was exposed.
  • I was slightly misquoted on The Consumeristno credit card information was found. My original post pointed out the potential for billing information to be found based off information I read about the iGo software.
  • The hard drive was wiped (by me) using DBAN and no copies of the original data exist.
  • Upon request demand of the owner the computer (and hard drive) were returned to them.


Tandy 102 Web Server

When I decided to start one of the first things I started to work on was hosting for the domain, since I was on a limited budget for the project I decided to host the domain myself rather then pay for hosting. The only thing I needed was a computer that I could use as a web server. Normally, getting my hands on a computer wouldn’t be a problem as I generally have at least one old system lying around. However, at the time my surplus of spare computers was limited; I had a couple of computers that I could have used but they were all dedicated to other tasks and I needed a dedicated system for the web server.

When cleaning out my garage I came across an old Tandy 102 Portable Computer. It didn’t occur to me at first, but later I wondered if somehow I could use the Tandy 102 as my web server. I started to take a look at the system and realized that being manufactured in 1987 it was never conceived that someone might want to use the Tandy 102 as a web server for their blog.

There were some definite problems that had to be overcome:

  • Very limited memory – 32K
  • Very limited storage – but it has an interface for a tape drive
  • No Ethernet port – but it has a modem

Through some trial and error I was able to interface a standard 80GB IDE hard drive with the tape drive port on the Tandy 102, I thought about using a flash drive which may have been easier to interface but I wouldn’t have gotten the storage I need. Getting the phone port (modem) interfaced with an Ethernet port was a bit more complicated but I was able to do it eventually. To get passed the memory constraints of the Tandy 102 I interfaced a 1GB USB flash drive to supplement its 32K. I decided early on in the project to use Ubuntu as the Linux distro, this made setting up the LAMP server easy as Ubuntu has a server distribution that has an automatic LAMP install. It took some doing but eventually I was able to get Ubuntu installed on the hard drive and get the Tandy 102 to boot form the hard drive.

After some configuration of the LAMP server I installed WordPress, configured the DNS settings for the domain to point to my home’s public IP address and the server was live. Overall I’m quite pleased with its performance at only 2Mhz it serves the site pretty well. It also has low power consumption and can run off 4 AA batteries for hours – built in UPS!

photo goodness: (click on image for full size)

Industrial Picture Frame

Industrial Picture Frame

This is an easy and cheap industrialish picture/poster frame I came up with a while back – it uses 1/8″ thick 3/4″ wide flat aluminum stock and some little alligator spring clamps; all of which you can pick up at Home Depot and the like. I’ve used this on larger (20″x30″) pictures but here I’m showing some smaller prints, whatever the size the method is the same.


Zero Point Shelf

Zero Point Shelf - SketchUp

If putting holes in the wall was a game this shelf wouldn’t net you any points. The image above is a very rough SketchUp drawing of a shelf I am going to start building over the next couple of weeks. The concept of “clamping” shelving between the ceiling and floor isn’t original to me, in fact I’ve see several variations of the idea; this is just my variation. The point of this method of mounting shelves is – you get the shelf without the holes in your wall, the concept also lends itself to being placed where there is no wall (stud) support.


Steal This Wi-Fi (the safe way)

In his Wired article “Steal This Wi-Fi” Bruce Schneier gives some good reasons to leave your wireless network open, being neighborly for starters. While being neighborly is nice, advising people to open their wireless network without providing some advice on how to do it securely is irresponsible and one would have expected more from a renowned security expert…

My blanket advice – close your wireless network. If you don’t know how, find someone who can help you.

On the other hand – if you know how to run an open wireless network securely then do it! It may be a geek thing, but I find it cool (and neighborly) to be able to run an open wireless network and provide passersby with free internet access.

Here is how I do it: