Comment by linker3000 | Hacker News Reader

Comment by linker3000 | Hacker News Reader

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* OWL power monitor with inductive clamp and separate LCD display (in the reduced bin at the local DIY barn), transmits data on 433MHz - £12

* Arduino Mega+ESP8266 combo board - £8

* Rflink Rx/TX board - order a kit or build your own (http://www.rflink.nl/blog2/wiring) 433 or 868MHz operation, can also work with some devices at 2.4GHz - About £15

* Rflink software (http://www.rflink.nl/blog2/) + Serial link software for the ESP8266 - all free.

* Configure the serial link software to talk to your MQTT broker (Raspberry Pi running Mosquitto and Node-Red)

You now have an rf receiver/transmitter system that can not only pick up and display your energy monitor signals, but also those of many other rf devices AND can record/re-transmit such signals too - in my case, I can get an alert when the doorbell rings + Capture shots from an IP camera, plus I can control a bunch of those cheap, remote controlled rf mains power sockets I've collected over the years.

Not as cheap as the SDR option, but with much more functionality

You can also buy clamp sensors that can be connected directly to a microcontroller (with an ADC - so not a Raspberry Pi without external hardware).

http://www.homautomation.org/2013/09/17/current-monitoring-w...

The clamp only systems lack accuracy due to not measuring supply voltage. Commercial/open source energy meters based on chips like the ADE7953[0] have a resistive voltage divider to attenuate the supply voltage to suitable level for the chip but preserving the envelope for sampling. The problem is there is no galvanic isolation, so interfacing is harder.

[0] http://www.analog.com/en/products/analog-to-digital-converte...

I have a similar set up with a Z-wave clamp style current meter[0]. This meter is calibrated to 120v. I use NUT to grab the line voltage off the UPS and adjust the reported current with actual voltage to get power. It's good enough for the girls I go out with

[0] https://www.amazon.com/Aeon-Labs-AEDSB09104ZWUS-Aeotec-Monit...

I have the same meter, that meter actually reports voltage to me though.

There are transformer isolated energy monitors like MAX78615. Much safer to work with.

Resistors are cheaper. Much better for the bottom line.

MAX78700 uses a pulse transformer for isolation from the MAX78615, and is powered by the '78615 via that same transformer. It uses resistors for voltage and current sensing.

If you got 3 phases going into your house, how would you use this sensor? Do you need 2, or even 3, of them?

True, though this isn't for everyone. To quote the article why the author didn't in this case...

...I HATE electricity. Too many years of geeky endeavors have resulted in far too many shocks, and mains electricity scares the hell out of me.

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