document PZEM-004T connection
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README.md
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README.md
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@ -52,6 +52,7 @@ DDM100TC
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This 3-phase 4-wire electricity meter provides an S0 interface.
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This 3-phase 4-wire electricity meter provides an S0 interface.
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On my model this would output 1600 impulse/kWh, thus each impulse corresponds to a power consumption of 0.625 Wh).
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On my model this would output 1600 impulse/kWh, thus each impulse corresponds to a power consumption of 0.625 Wh).
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This rate is hard coded in `main.c`.
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To record these impulses a timer input capture is used.
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To record these impulses a timer input capture is used.
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The number of impulses determines the energy used.
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The number of impulses determines the energy used.
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It is stored in a backup register, keeping the value in memory even when the board is powered down as long as a (coin cell) battery is connected to VBAT.
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It is stored in a backup register, keeping the value in memory even when the board is powered down as long as a (coin cell) battery is connected to VBAT.
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@ -61,7 +62,27 @@ The time has a resolution of 0.91 ms (leading to a power calculation error of <1
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Connections DDM100TC <-> board:
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Connections DDM100TC <-> board:
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- S0+, pin 8; +3.3V or +5V
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- S0+, pin 8; +3.3V or +5V
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- S0-, pin 7; TIM4_CH1, PB6 (use pull-down resistor)
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- S0-, pin 7; PB6, TIM4_CH1 (add pull-down resistor)
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PZEM-004T
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This 1-phase 2-wire electricity meter provides a UART interface.
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For the 3-phase 4-wire power distribution installation I used 3 meters, one per phase.
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Because each command includes a device address, they can be connected to the same UART port (one individual addresses have been set).
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All meters are periodically (see RTC) sequentially queried for their measurements (voltage, current, power, energy).
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The used addresses are hard coded in `main.c`
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A timer is used to guarantee a minimum (undocumented in the specification) time between requests in order to improve the response success.
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Connections 3xPZEM-004T <-> board:
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- 5V, 1; +5V (+3.3V is not sufficient)
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- RX, 2; PA2, USART2_TX
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- TX, 3, PA3, USART2_RX
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- GND, 4; ground
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Note: when connecting multiple meters one the same UART bus only keep one of the pull-up resistors (across all meters) on the TX pin (on the opto-coupler output), else the low level is not low enough for the micro-controller to correctly decode the signal.
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ESP8266
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ESP8266
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