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Meeting Recap: August 2011

Thanks to all who attended this month's club meeting... our annual Parts Swap! This is one of our favorite events of the year, bringing out old kits, half-built projects and scads of moldy, left-over parts from the bottom of the junk boxes. But one man's junk is another's treasure, and boy did we have some good stuff on the tables this time.

Here's just a smattering of the "transactions" made during the day:

Joe Jesson, KC2VGL, told us about a QST sidebar (June 2009, p31) where Skip Teller mentions using Fligi's DominoEX8 protocol and how it works over much greater DX than FM voice. This could give everyone in NJQRP who owns a garden-variety FM rig at, say, 145.00 MHz, some coding gain over voice and we could have a sched with the group.

New member Frank N3PUU was in attendance - welcome! Frank discussed the power and battery monitors he is building and sent us these additional details:

"First is the whole house power monitor. This is based entirely off of Trystan Lea's Open Energy Monitor project. I took his "non-invasive" design and adapted (basically doubled) the code to monitor the split phase found in the US. I also added a few lines to drive a 4x20 LCD. The current transformers came from Seeedstudio (I've now also seen them in other places as well), Model SCT-013-000, 100A rated . For this project, I simply embedded a Arduino compatible board with serial interface . Voltage monitoring comes from a small radio shack transformer I had in the junk box. A separate (same model) transformer acts as the power supply. Instead of fly-wiring everything, I made up a carrier board to hold the Arduino board and the needed external components. I don't have this mounted up in an enclosure yet (trying to get access to a mill to make a clean LCD cutout), but here are a few pictures of it running on the bench: powered up and monitoring a desk lamp , the display, the bare carrier board, and the carrier + Arduino. In addition to the LCD display, the current information is piped out the serial port. I run this data into a Linux box with a simple shell script that aggregates the data and then generates usage graphs with RRDTool. Here's a sample graph.

Next is the battery monitor that I am attempting to design and build. This is another Atmel project (again using the Arduino language), however on this one I want to eliminate the seperate board and run the Atmega directly. The goal with this project is to be able to accurately monitor the battery bank found in an RV. For the measurements, Texas Instruments makes the INA219 chip, which is a bidirectional current/power monitor that speaks I2C. This is a pretty slick little chip that monitors a shunt and will report Bus Voltage, Charge/Discharge Current, and Power over I2C. It is a tiny little thing in an SOT23-8 package, for reference here's a picture of some breakout boards I made to breadboard this thing. Four of these fit very comfortably in a square inch! I'm currently testing the design on the breadboard , and slowly working through the code. So far I have it reporting voltage and current and am about ready to move onto the monitoring calculations. Here's the test rig and one more a little closer ."

Nancy NJ8B came all the way from her WV home for this event. And a special thanks to Nancy for bringing so many nice items for the club members ... at no cost!

Per usual, a number of us had a good breakfast before the meeting at the Metro Diner just down the road. And afterward too, as it is becoming a tradition to have lunch at the same diner after the meeting. Overall, a great day.

73, George N2APB
& Joe N2CX

Last updated: November 27, 2011