emonTx V3 Progress Update

Since my last post introducing the emonTx V3  prototype design progress has been steady. The design has undergone several iterations and has now reached a stage of maturity.

The main features of the emonTx V3 have stayed the same:
  • ATmega328 Arduino IDE compatible microcontroller
  • RFM12B or Ciseco SRF 433/868/915Mhz RF wireless compatiable with RFM12Pi Raspberry Pi emoncms basestation
  • 3 x Standard (23kW max) CT channels
  • 1 x High sensitivity (4.5kW max) CT channel 
  • Integrated AC-DC power supply to enable powering the unit from a single 9V AC adapter while also sampling the AC voltage to calculate Real Power and AC Vrms readings 
  • Low power design with option to power from 3 x AA batteries for Apparent Power (current ony) measurement
  • Enclosed in wall mountable extruded aluminium enclosure
  • Terminal block connection for optical pulse sensor and DS18B20 temperature sensors
  • Pre-assembled SMT electronics
emonTx V3 with 3 x AA battery's and 1 x CT (Apparent Power setup)
Fully assembled with antenna in wall-mount enclosure

I am currently in the process of obtaining assembly quotes from manufactures as well as performing lots of testing.

emonTx V3.1 PCB Design 
emonTx V3.1 Schematic

The AC-DC circuit that was initially designed with the aid of simulation then bench tested is performing as expected.

Blue = output from 9V AC adapter Yellow = input to voltage regulator when unit is drawing 7.7mA  @ 3.3V, sudden dip is caused by RFM12B firing up to transmit four integer data packets (approx 24mA for 2.7ms)
If all goes well we're expecting to get the emonTx V3 into production in the next few of months.

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