Bob Cochran's Tech Photo Gallery

September, 2008

I built a Sanguino board (which is among the clones of the Arduino physical computing devices) and have it blinking LEDs quite nicely. Click the photo to read about the build experience and see my projects as time goes on.

My DSL service started dropping intermittently beginning in late June. I learned how to work with telephone hardware. The full story of the phone wire replacement project is coming soon.

June, 2006

Know When The Mail Arrives – 433.92 MHz Transmitter Circuit

This is the beginning of a circuit featuring a 433.92 MHz transmitter which will detect when a mailbox door has been opened. The circuit design follows the one published in the June 2006 issue of Nuts and Volts magazine ("Mail Delivered Detector", by Charles Irwin, see p. 45 for the transmitter circuit diagram.) I'm using Radio Shack 276-158B perfboard and this view is the solder side. What I'm doing here is connecting pin 1 of the CD4013 to the base of the 2N4403 transistor with a 10K resistor. The collector of the 2N4403 is connected to pin 3 of the TWS 434A (the blue wire.) I have not yet connected the emitter pin to power. Pin 14 (V+) of the 4013 is connected to the positive pin of the 1000 microfarad electrolytic capacitor with the orange wire. The negative pin of that capacitor is connected to ground by the green wire.

I figure I can connect my SPL-606 photovoltaic cell clips directly to the + and - pins of the 1000 microfarad capacitor (or to headers which are then connected to the cap), and connect every other ground connection to the green wire you see (in effect making a home-made ground plane by gooping solder onto the pads adjoining that wire and bridging them.)

You can see where I had a problem with my hacksaw and messed up the lower right corner of the perfboard.

November, 2004

Get More Wireless Range With A Cantenna

I like to set up a table in my yard on pleasant days, bring my laptop and a stack of books outside, and program away. There are two problems with this. My Buffalo wireless card in the laptop often can't connect to the wireless access point in the house just where the yard dips below the house. I couldn't check my email. And from late spring to late fall, the mosquitoes drive me crazy. To fix the connectivity problem, I built this cantenna. A cantenna is a waveguide antenna built inside a tin can. It offers better reception than what the tiny antenna built into the the wireless card can hope to achieve. Inside the tin can is a carefully positioned antenna probe which I soldered to the connector. You can't see the probe too well in this photo. It is a short piece of #12 solid core copper wire. The wire runs from the connector on the can to wireless card, which has a tiny jack in it for external antenna connections. Not all wireless notebook adapter cards have such a jack. I ordered this card because it had one. The connector and wire I purchased as a "cantenna kit" from Fleeman, Anderson and Bird. They sell several cantenna kits featuring different connector types. The tin can is a Campbell's Family Size Chicken Noodle Soup can bought at my grocery store. (The Family Size can is larger than the "regular" size Campbell's cans.) I also bought a citronella candle to help shoo the pesky bugs away.

If you have comments my email address is given below, slightly modified to confuse spammers. You should be able to figure out how to reconstruct the address.

Robert L. Cochran ( cochranb a tt speakeasy.net )

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