Category Archives: Nerdery

External power and non-Nikon batteries on the Nikon D3100

_DSC8718, originally uploaded by afiler.

The Nikon D3100 is a great camera for the price, the bottom end of Nikon’s DSLR range. Being a bottom-end camera, a few things are missing, like an external power connector. I’m using this camera in a fixed setup for slide scanning. The 1080p live view makes an excellent way to preview slides on an HDMI monitor, but this will drain the battery quickly. One option is to use the Nikon EP-5A, which is basically a battery-like plug for the camera, which then attaches to the Nikon EH-5A power supply. This will run you about about $108 at B&H. A spare battery will run you another $50. None of the third-party batteries available apparently work in the D3100, as Nikon puts some sort of inkjet cartridge-style money-sucking chip inside their batteries. (I’m sure the vast camera accessory factories in China are working to overcome this issue).

It turns out the answer to both these problems is a third-party D3100 battery grip, $20something from Amazon.


The left-hand battery slot in the D3100 will take the $8 third-party batteries, as the camera is happy as long as it can see a Nikon battery when it starts up. I decided to add a barrel type power jack so I can power the camera off a power supply. I suppose it’s possible that all these infidel non-Nikon parts could cause the camera to explode, so don’t try this at home, kids.


The battery grip contains a circuit board that runs the whole width.


I attached the barrel plug to the left-hand (“infidel”) battery slot. In this photo, Green is – and White is +. Most DC power supplies are center-positive, and so I used that scheme here. I picked a spot for the barrel plug that puts it right against the battery slot so it can’t easily pop out. I carefully drilled a hole in the case, squared it off, and hot glued it in.

It works perfectly. You can even remove the genuine battery once the camera is booted.

My clock. It ticks.

201_0291.MOV, originally uploaded by metrixcreate.

My clock. It ticks.

My new internet radio

My new internet radio, originally uploaded by afiler.

It has knobs like a real radio, but yet it plays modern radio stations. There’s no screen yet, but one is coming.

I use an Arduino to connect the switches and selector knob to the computer inside, and it uses mpd (the music player daemon) to tune through a playlist of internet radio stations. Code for that is at

Apple II Plus as a USB keyboard

Connecting an Apple II keyboard to a computer with USB is surprisingly easy with a Teensy board. The Apple II uses an ASCII keyboard, which means that rather than returning scan codes, it returns a 7-bit ASCII value. This also means you can’t read the state of modifier keys like shift or control independently. The Apple II keyboard in particular doesn’t even support lower-case letters (though I’ve made a bit of a hack for this). They even re-use a couple alpha keys for other characters, so shift-P makes @ and shift-N makes ^. Other late 70s/early 80s home computers like the TRS-80 had a really simple layout like the Apple II’s (though the TRS-80 had all four arrow keys but no Control key). I may have to try out adapting some other weird old home computers as USB keyboards — the C-64 seems like it would be a good shape/size for that.

Arduino (Teensyduino) code is available at

Extending a keyboard with LASERS

Photo by Duncan at Metrix [flickr stream].

Since Unicode “works” in most places on the internet these days (from webpages to Twitter to IRC in terminal sessions), I like to use all the characters that are available to me, when they make sense — like “99¢” or “-40°”. I decided go to Metrix and laser many of the characters accessible from Alt(Gr) into the keycaps on my MacBook Pro. The keyboard is backlit and lasering the key exposes the clear key underneath, so it turned out quite well. If I’m feeling like there still isn’t enough visual interference on my keyboard, I may decide to laser on the AltGr and Cyrillic characters too.

Hello, m’am, I’m from the Phone Company

_DSC2454.JPG, originally uploaded by metrixcreate.

Duncan and I made tshirts with the “phone company” logo on them (no actual phone company has this logo, but it looks a lot like the logo of some random independent phone company in the 1970s.

They were screen printed, but with a plastic stencil instead of a photo-process “stencil”. I bought a book of polypropylene sheets from Dick Blick (“suitable for water color”, the cover says), and got the stencil cut on the laser cutter at Metrix. They can’t cut vinyl or other chlorine-containing compounds, as deadly chlorine gas will be produced (though in quantities that would probably be more damaging to the laser than to humans), but polypropylene works great.

Instant document conversions

Want to squeeze a text file out of a Word document you found online, or need a CSV from an Excel file? Use! For example,

This will give you an HTML version. If you’d like a different output type, insert that type’s extension in front of the URL. For a plain-text version instead, for example,

PDF, HTML, text, CSV, XLS, and DOC output formats are supported on the relevant data types. I’ll soon be adding ImageMagick support to convert from zillions of image formats, and conversions to/from .SHP shapefiles, KML files and other geodata should also be supported soon.

Want to know what input document types are supported? Just try the link. If it works, then that document type is supported. If it doesn’t work, then that document type isn’t supported.

More finger features

My finger gateway now supports much more of the Internet. It supports some sites specifically, like Facebook (try finger, but it also supports sites that have per-user RSS feeds linked to from the page at (e.g. finger It also supports queries on sites that have RSS feeds linked from their main page (e.g. finger

More finger feature suggestions are welcome!

I made a monitor stand

I made a monitor stand out of black gas pipe and fittings, compression tees, and an adapter bracket.

The compression tees (as in pipe fittings, not clothing) were an awesome find. They have rubber gaskets inside that made a surprisingly tight connection once the end caps are screwed down.

The galvanized metal fitting is a bracket made for using metal pipes for things like mounting rails and chin-up bars. The holes are 38mm apart, as opposed to 100mm on the standard VESA mount, so I made an adapter bracket. I made the adapter out of 6mm birch on the laser cutter at Metrix Create:Space though it would be easy enough to make at home — but lasering’s just so easy! I even countersunk screw holes using the laser.

I’m really impressed with the stability of the stand. I had been worried I’d need to add clamps under the compression tees to make sure they wouldn’t slip, but it turns out they’re far more solid than expected.

If I ever go completely insane and decide I need more monitors, I’m thinking I could make an X-Y setup, with two vertical bars, on which horizontal bars could be mounted. Each row could still have its height adjusted, plus this would allow an up/down tilt on each monitor.

Total cost for this was about $70, $8 of which was for the (very optional) laser cutting.

Top Telephone Switches

With AT&T saying that “with each passing day, more and more communications services migrate to broadband and IP-based services, leaving the public switched telephone network (“PSTN”) and plain-old telephone service (“POTS”) as relics of a by-gone era,” I thought it would be a good time to get a snapshot of the North American telephone network as it exists now. In the early 1970s, phone phreaks like Evan Doorbell and Mark Bernay started recording what they saw as the demise of the electromechanical telephone network. The switches then were crossbars and panels and steps and the like, with early computerized switches like the 1ESS just starting to appear. Now, the 1ESS is nearly gone from the network, and the North American network consists mostly of the Western Electric/AT&T/Lucent/Alcatel 5ESS (the 1ESS’s successor), the Nortel DMS-10 and DMS-100, the GTE Automatic Electric GTD-5 EAX, and the Stromberg-Carlson/Siemens DCO. A few other switches in the network, like the Siemens EWSD and the Ericsson AXE 10 have found more popularity in North America as cellular switches (and as wireline switches in other countries).

The oddball switches are the ones that really interest me, and they’ll be the first ones to disappear from the network. I’ve been told that the TRW Vidar ITS-5 and the Mitel GX5000 switches may be gone from the North American network. To see what might be left, I decided to do some digging, and I’ve come up with a list of the telephone switches (minus remotes) still in use in the North American network. There’s undoubtedly some stale data in this database, and so for rare switches, I think the numbers listed are the upper boundary — the lower boundary may be as low as 0. The list also contains the mystery “Digital Switching System”. There seems to be an awfully large number of them for it to be the North Electric DSS-1, which became the ITT 1210 — maybe it just means “unknown digital switch”?

The picture above of the GTD-5 EAX was shamelessly stolen from the site of a GTD-5 consultant, the only place I could find a picture.

Top 10 Switches

Manufacturer Switch Count
NORTEL DMS 100 2513
NORTEL DMS 10 1968
REDCOM MDX 384 155

Continue reading