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Powermon433

ATmega (Arduino) decoding of Blue Line Innovations PowerCost Monitor™ and Black & Decker Power Monitor EM100B real time household electricity consumption data. Forked from CapnBry/Powermon433 to provide a simple serial logger and some usage instructions.

Tested with:

  • OSEPP (Arduino) Fio + RFM69W (3.3 V logic, FTDI serial interface required)
  • Arduino Uno + RX3400-LF-based superheterodyne receiver (5 V logic)
  • Arduino Uno + Parallax 433 MHz RF Transceiver (#27982) (5 V logic)

A working PowerCost Monitor™ or Power Monitor EM100B (the meter transmitter is identical) installation is assumed.

Quick Start

  1. Wire up one of the “Tested with” options above, according to the receiver notes below. The Arduino + superhet receiver option is cheapest (but has a minor fiddle with trimming the wire antenna to length), the Arduino + Parallax transceiver is simplest (but expensive), and the Fio + RFM69W is fiddliest, mid-priced, but has a lovely robust receiver.
  2. Upload the included sketch, and open the serial monitor or serial terminal (38400, 8N1). You should soon see some CRC ERR messages scroll by, a couple a minute or so.
  3. Go out to your meter, and briefly press the button on the monitor sensor. The red LED in the battery window should start to flash.
  4. You should see a New ID message in the output, followed by a hexadecimal number. The CRC ERR messages should soon be replaced with energy (Wh), instantaneous power (W) and outside temperature readings. Energy and temperature take a couple of minutes to come in, so will start at zero.
  5. (Optional, recommended) Note down the device ID, and change the #define DEFAULT_TX_ID 0xfff8 line in the Arduino sketch to use your device ID. This way, your installation will default to decoding your meter, and won't need the monitor button pressed every time you restart your Arduino. Once you're satisfied that you have your ID set correctly, you may wish to ‘lock’ the ID by uncommenting the #define TX_ID_LOCK line and re-uploading the sketch to your Arduino.
  6. (Optional, at-best-tolerated) If you must use °F, uncomment the #define TEMPERATURE_F line. But don't blame me if you get haunted by ghostly 18th century European oxter guff …

If you're having difficulties, Bryan's original sketch prints more diagnostic messages than this one. If you are using a wire antenna, check it's the right length …

Stewart's Receiver Notes

The RFM69 receiver boards described by Bryan (see below) are lovely, but:

  1. They're 3.3 V logic
  2. They use 2 mm pitch headers instead of the “standard” 2.54 mm

If you don't want to use an RFM69, you really want to use a superheterodyne 433.92 MHz receiver instead of a super-regenerative receiver board.

A superheterodyne board:

  • is cheap
  • has one decently-sized chip on board (the RX3400-LF is 24-pin SSOP), which may be covered in a metal shield
  • has a crystal (typically 6.773 MHz for 433.92 MHz RX frequency)
  • has no obvious coils or tuning chokes

A super-regenerative board:

  • is very cheap
  • typically only has one small chip (like an 8-pin LM358 op-amp)
  • has no crystal
  • has a coil and a tuning choke
  • doesn't work for this application.

Superheterodyne wiring

These boards often have repeated pads. The one I'm using (marked “3953 A434”) works for me when connected as follows:

Board   Arduino
=====   =======
 GND  → GND
 DATA → D8
 DATA → D8
 +5V  → 5V
  …
 +5V  → 5V
 GND  → GND
 GND  → GND
 ANT  → Antenna (164.5 mm wire as simple ¼-wave monopole)

The antenna length is critical. I had initially cut mine to 168 mm, and it didn't work at all.

Parallax 433 MHz RF Transceiver Wiring

The Parallax 433 MHz RF Transceiver uses a Linx TRM-433-LT transceiver chip, and comes with a nice stub antenna attached. Wiring is simple:

Board       Arduino
=====       =======
 1 GND   → GND
 2 VIN   → 5V
 3 DATA  → D8
 4 TX/RX → 5V
 5 PDN   → GND
 6 RSSI  → not connected

Although this board is expensive, it's:

  1. relatively easy to find in hobby electronics shops
  2. already got a properly trimmed antenna.

If time is money for you, the Parallax might be a good option.

Bryan's Receiver Notes

Data line from a superheterodyne receiver should in run to pin Digital 8. I've tried using a superregenerative receiver but the sensitivity was too low to receieve anything. Your results may be better than mine.

To use an RF69 / RFM69W / RFM69HW / RFM69CW / RFM69HCW connect:

RFM     Arduino
===     =======
NSS  → D10
MOSI → D11
MISO → D12
SCK  → D13
DIO2 → D8
ANA  → Antenna (164.5 mm wire as simple ¼-wave monopole)
GND  → GND
3.3V → 3V3

With the RF69 module, a frequency of 433.845MHz is tuned with a 50khz receive bandwidth. My module can receive data on this frequency right down to a 1.3Khz bandwidth so I am pretty sure this is accurate. The AFC and FEI blocks don't appear to work no matter where I trigger them, so I can't use them to adjust the frequency. Perhaps they only work on FSK and this is ASK/OOK.

Standard auto LNA gain and 'peak' mode OOK threshold are used which does a good job of adjusting receiver sensitivity. The module registers are assumed to be at their default values on startup, so be sure to reset the module if switching from code that uses packet or FSK mode.

Use a 164.398mm wire antenna for quarter wavelength monopole.

RUNNING AS A DATA LOGGER

Included in this package is a not-very-well-thought-out example script loop.sh you can run to log data from your power monitor. Check the comments for requirements.

THE ARDUINO RESET

Arduino boards reset if a new serial connection is made. It's by design more than anything else, but is annoying if you're making many short logging runs. In theory, for an Arduino Uno, you can put a 10 µF capacitor across, but I haven't had much success with that.

As I'm only logging a file once a day, it's not so much of a problem for me.

ADDITIONAL NOTES

The temperature decoding may not exactly match the display, mainly because we're using a simple lookup table and interpolating values. The temperature sensor can be inaccurate anyway, as it's in a black box often in full sun, and it will often read +10°C over ambient.

BUGS

  1. Yes, I'm sure there are.

TODO

  1. Uninitialized values output 0 rather than “NaN” or something more appropriate.