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mmakaay / dsmr-reader-for-esphome

A smartmeter project, made for ESPHome (hardware + ESPHome config)
MIT License
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Improve power stability on DSRM v4 without need for power supply #8

Open f-idelio opened 1 year ago

f-idelio commented 1 year ago

added modification with 2 x 6.3V 3300uF instead of the original 1000uF capacitor.

mmakaay commented 7 months ago

I'm not sure what the exact advantage is of using this. Are there any specific electrical advantages of using this setup? Does something work that would not work with 1000uF? This pushes capacitance to 6600uF, which is a lot.

f-idelio commented 6 months ago

This solves the issue related to DSMR4.2 max current limit and the power hungry D1 Mini boards (up to 250mA during peaks, eg. with bad wifi signal strength as in my case). In such situations the 1000uF is simply not enough to buffer the power needs during the peaks and not have the input voltage drop with the D1 Mini shutting down due to undervoltage. I first tried it with an added charge pump to overcome this. Though the DSMR4.2 interface is so capped that a charge pump does not work. So increasing the 1000uF capacitor was the only way to get it working. I tried several capacitors that fit the dimensions of the PCB layout. and 2x 3300uF fit the PCB layout and solved the issue in my setup (weak wifi signal and thus extra power hungry). 6600uF might seem a lot but you have to keep in mind that you can only use a small portion of the stored energy in a simple buffer capacitor before you get a voltage drop.

As I tried to explain in my edit of your readme.md: The DSMR4.2 P1 port is current (up to 100 mA) AND voltage regulated (5V). The ESP8266 D1 Mini boards have short term power peaks while connecting to wifi or transmitting over wifi. With low wifi reception the peak draw can be up to 250 mA for 5-15 milisecond. This is exceeding the DSMR v4 P1 port electrical specification by far. In such cases the output voltage of the ESP8266 D1 Mini on board power regulator will drop and result in a reboot. This will happen over and over again. Increasing the capacity of the capacitor significantly can help to overcome this.