Emontx v3.4 – openenergymonitor wiki electricity symbols and meanings


The emonTx V3.4 is the latest version of the emonTx Low Power Wireless Energy Monitoring Node designed for monitoring AC electrical power on a maximum of 4 separate (household/building) circuits using non-invasive clip-on CT sensors and an AC-AC Voltage adapter to provide a voltage signal for Real Power calculations. The emonTx V3.4 is a minor update to the emonTx_V3

The red LED indicator will illuminate for a couple of seconds then extinguish never to flash again if powering from a DC source. If the LED flashes multiple times at startup this indicates the emonTx is detecting an AC waveform – this can happen if an AC adapter has just been removed, hit the reset button if this occurs. When powering the unit via 5V USB/battery it is advisable to remove the JP2 jumper if an AC-AC adapter is present. Powering via AC (4)

A nice feature of the emonTx V3 is the ability to use an AC-AC adapter to power the unit while simultaneously providing an AC voltage sample. If the emonTx V3 detects the presence of an AC adapter at startup, it will automatically implement Real Power and Vrms measurements by sampling the AC voltage. electricity word search j farkas answers Real Power is what you get billed for, and depending on the appliances connected to the circuit being monitored, can vary significantly from Apparent Power – see Building Blocks for more info on AC power theory. For best energy monitoring accuracy, we recommend powering the EmonTX with an AC-AC adapter whenever possible.

Using the AC voltage for reference also enables the emonTx to monitor the direction of current flow. This is important for solar PV monitoring. gas pain left side If you notice a negative reading when you were expecting a positive one, reverse the orientation of the CT on the conductor. The red indicator LED will flash at startup then flash once every 10 seconds to indicate an AC waveform has been detected. Sleep mode will be disabled to keep a more consistent power draw on the AC circuit.

Important note regarding powering with AC: powering via AC is recommended only for standard emonTx operation without auxiliary sensors (apart from a maximum of 4 DS18B20 temperature sensors) or equipment (e.g. relay modules) connected. Correct operation via the AC supply is critically dependent upon using the correct AC-AC adapter. la gas prices average If you are using the recommended AC-AC adapter and the current draw exceeds 10 mA and the mains supply is below the minimum allowable, then circuit operation will be impaired, adversely affecting the accuracy of the emonTx. To avoid damage to the emonTx V3 circuits, the current drawn from the AC circuit should never exceed 60mA – see the technical wiki for more info. If more than 10 mA of current is required, it is recommended to remove jumper 2 (JP2) and power the emonTx via the 5V mini-USB connector. When JP2 is removed, the AC-AC adapter (if connected) will be used only to provide an AC voltage sample, i.e. it will not power the emonTx. Uploading Firmware

All emonTx V3s sold pre-assembled with a radio module are shipped with Discrete Sampling firmware. gas up the jet This is the main firmware for the emonTx V3 and has been tested and calibrated based on nominal component values. If better accuracy is required, and facilities are available, the unit should be re-calibrated to take account of variations present in the components used. You will need access to a programmer to reload the sketch.

The emonTxV3_RFM12B_Discrete Sampling firmware samples 10 full AC cycles, i.e. 200 ms per measurement from each CT at a rate of approximately 2500 samples per second. It is assumed the power does not fluctuate significantly during the time the microcontroller is asleep, which is usually good enough for typical household monitoring. p gasket 300tdi If greater precision is required (as is the case with PV energy Diversion it is recommended that you use a PLL or continuous sampling sketch. See the RFM12B firmware examples folder on GitHub.

A DS18B20 digital temperature sensor can easily be connected to the emonTx V3 by connecting the sensor to the emonTx V3 screw terminal block or RJ45 connector. The default firmware (discrete sampling) supports auto-detecting one DS18B20 sensor. Multiple DS18B20s can be daisy-chained, but this will require changes to the pre-installed emonTx firmware – you may also run into power draw issues depending on how you are powering the emonTx (see Power Supply Options above).

In order to save power when running on batteries, the emonTx V3 supports switching off of the DS18B20 in-between readings and performing the temperature conversion while the ATmega328 is sleeping. To do this, power (3.3 V) is supplied to the DS18B20’s power pin from Dig19 (ADC5), this digital pin is switched off between readings. (This facility is available only if the temperature sensors are connected via the terminal block.) The data connection from the DS18B20 is connected to Dig5, this I/O pin has a 4K7 pull-up resistor to 3.3 V on-board the emonTx V3’s PCB, as required by the DS18B20.

In the case of an electricity meter, a pulse output corresponds to a certain amount of energy passing through the meter (kWh/Wh). For single-phase domestic electricity meters e.g. Elster A100c, each pulse typically corresponds to 1 Wh (1000 pulses per kWh). gas exchange in the lungs takes place in the Water and gas meters will usually be marked to show the quantity of water (litres/gallons) or gas (cubic meters/cubic feet) that each pulse represents.

Pulses and the most recent pulse count are transmitted via RF, as the final variable in the JeeLib packet structure. The emonCMS wh_accumulator input process can be used to log the pulse count. The wh_accumulator input process detects when the pulse count gets reset to zero (after the emonTx is reset) and continues to accumulate, ignoring the reset. A scaler input process can be used to convert number of pulses to kWh. For example: my utility meter outputs 800 pulses per kWh, so each pulse is 0.8Wh. I can multiply the number of pulses by 0.8 to get the number of Wh, or by 0.0008 for the number of kWh accumulated.

There is an pull-up resistor connected to the pulse (IRQ) input that is enabled in the standard sketch. electricity generation Therefore, you can connect a volt-free contact or an SO output between screw terminal 4 / RJ45 pin 6 (IRQ input, SO+) and screw terminal 3 / RJ45 pin 5 (GND, SO-) without the need for an additional resistor. If you must connect your contacts between VCC (screw terminal 2 / RJ45 pin 2) and screw terminal 4 / RJ45 pin 6, then you must add a pull-down resistor of resistance low enough to overcome the internal pull-up resistor, or you can use a higher-value resistor and modify the sketch to disable the internal pull-up.

if you have an Elster meter (tested with Elster 100C) the emonTx V3 with an IR TSL261R sensor can be used to interface directly with the meter protocol to read off the exact accumulated watt hours that you have generated or used. This reading can be used on its own or to cross-check and calibrate CT based measurement. gas leak los angeles See here for original blog post Connectivity RF Link

Both the Raspberry Pi and emonTx v3 run at 3.3V so the serial Receive and Transmit lines can be connected directly. The 5V power rail from the Raspberry Pi can be supplied to the emonTx which is then stepped down to to 3.3V by the emonTx voltage regulator. 5V is provided by the red wire (see photo). The ground connection is the black wire and the serial data going from the emonTx to the Raspberry Pi is the green wire. Wire for serial data going the opposite direction (Pi to emonTx) has not been connected in this example but could be added if two-way communication is required.