$24 Eastron SDM120C Smart Meter Supports RS485, ModBus, Up to 45A Load

A couple of days ago, I wrote about Sonoff POW R2 WiFi switch with power monitoring function that meant to be connected to your mains via terminal, and I was made aware of another product – Eastron SDM120C – that also does power metering, but support up to 45A (good enough for whole house in many cases), and use RS485 / Modbus communication instead of WiFi.

I’ve also noticed it’s compatible with Domoticz with source code released on Github, so it might be worth a look.

Eastron SDM120C specifications:

Rated Voltage (Un) – 220/230V
Voltage Range – 0.8~1.2 Un
Base Current – 5A
Max. / Min. Current – 45A / 0.25A
Frequency – 50/60Hz
Remote Reading – RS485 port using Modbus RTU protocol
Pulse Output – Pulse 1: 1000/100/10/1 imp; pulse 2: 1000 imp/kWh
Power Consumption – <2W/10VA
Safety / Certifications:
- AC voltage test – 4KV for 1 minutes
- Impulse voltage test – 6KV @ 0.5J open circuit
- Over current test – 30 Imax for 10 ms
- Mechanical environment – M1
- Electromagnetic environment – E2
- Electrostatic Discharges – 15kV air gap as per IEC 61000-4-2
- Electromagnetic RF fields – 80-2000 MHz as per IEC61000-4-3
- Electrical Fast transients – 4kV as per IEC61000-4-4
- Surge Test – 4KV as per IEC61000-4-5
- Conducted Disturbances – 10V as per IEC61000-4-6
- Emissions – EN55022
- Climatic Influences – IEC60068-2
- IP Rating – IP51
- Resistance to Heat & Fire – IEC60695-2-11
Dimensions – 119 x 62 x 17.5 mm (35mm DIN rail mount)
Temperature Range – -25 to +55°C

With this type of a deice you’ll want to make sure it’s certified for safety, and it appears to follow many different safety standards, but I’m not knowledgeable enough to confirm whether those are sufficient for Europe. Note that the device is only for 220-230V, so it won’t work in the US. The company claims to have 110V versions, but I could not find them on Aliexpress.

SDM120(C) is sold for $22 and up on Aliexpress, but you’ll also find SDM120 A – which looks similar – , but with single pulse output and a different display, for $11.70. The Domoticz documentation also relies on a RS485 to USB converter for connecting the smart meter to your automation gateway.

Thanks to Gaetano for the tip.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.