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Open-source tools for energy monitoring and visualisation
Updated: 8 hours 28 sec ago

emonTx V3 Antenna Testing

Wed, 12/03/2014 - 13:57
Today we did some quick testing regarding using different antennas with the emonTx V3. 
Four antenna options were tested (Farnell part numbers listed for SMA antennas) :

Note: the graph sub-title has a typo, it should read 'RFM69CW', 'CRW' module does not exist.. At least to my knowledge! 
It was found that the wire-whip antenna as shipped by default with the emonTx V3 performed best. 
However using an SMA could be preferable in some environments; it's more robust and can  be extended easier. 
Now we have a way to measure RSSI (received signel strength indicator) using  an rfm69cw module we plan  to  do some more antenna and range testing. I'm interested to test to see how many db we're loosing in the antenna pcb trace from the module to the RFu328 then the emonTx V3 pcb trace then finally into the 90 degree sma connector. In future version will probably but the rf module and MCU directly on the PCB keeping the antenna trace as short as possible and use an edge mounted sma connector (these are also cheaper and easier to solder in manufacture). 
For more info on the test see the emonTx V3 wiki page:
Categories: Blog

Direct connection emonTx V3 > Raspberry Pi GPIO

Fri, 07/03/2014 - 16:58
Sometimes it's more convenient to connect the emonTx V3 directly to a Raspberry Pi base station rather than use RF. Both the Raspberry Pi and emonTx V3 run at 3.3V so the serial Rx and Tx serial lines can be directly connected. The raspberrypi's 5V supply can be used to power the emontx which is then stepped down to to 3.3V through the emonTx V3's voltage regulator. 5V is provided by the red wire. The ground connection is the black wire and the data going from the emontx to the raspberrypi is the green wire. I haven't connected a wire for serial data going the other way but this is a possible option if two-way serial is required.
emonTx V3 > Raspberry Pi Connection 

Here's a simple direct serial output sketch for the emontx v3 on GitHub hereOn the raspberrypi if you just want to forward the emontx data to a remote emoncms this can be done with the oem_gateway developed by Jerome which is on the standard rock solid forwarder imageSee our blog post about how to configure the oem_gateway for work over a serial link rather than RFM12B 
This info was taken from the emonTx wiki and written up after a forum thread
For the future we are working on developing an energy monitoring shield for the Pi to create an all-in-on Pi-energy-monitoring unit, see dev forum thread:
Categories: Blog

Emoncms developments and calculating wh totals on the emontx

Mon, 03/03/2014 - 20:59

Rather than posting at length about development on the blog, I've posted what I've been working on recently on the forums, here are links to the posts:

Development: Calculating Wh totals on the emontx

Emoncms development

Categories: Blog