Hello all, i am working on a project named "SMART ENERGY METER USING ARDUINO". I wish to store kwh reading in every second to my SD card, is it possible to write data on sd card in infinte time unlike EEPROM of arduino? Thanks in adavance
Define infinite 
Life expectancy applies to a single cell in the bult-in EEPROM and to a sector of 512 bytes in an SD card. So writing the same cell or sector time after time reduces the life.
- It's unlikely that you will write the same area on SD every time; you will write a file on SD so that will result in consecutive areas being written.
- SD cards have built-in wear leveling to prevent you from writing the same area time after time.
What technique is used to write data on energy meter for many many years? When the power cut off energy meter stores its kwh readings and write again after supply on
I don't know; I suggest that you open one up and have a look inside.
Options that I'm aware of are:
- EEPROM (internal or external)
- Battery backed RAM
- FRAM
- SD
Are you storing just the last reading? Or are you recording over a period of time?
I will store my kwh readings in every loop
Not sure what that means, but sounds like a very bad idea!
Why would you want to log KWH every second? That doesn't rise very much over a second for general household use.
Is your actual issue about trying to make sure the data isn't lost if a power loss occurs? Is the storing of KWH every second supposed to make sure that the most recent KWH reading is never lost?
A much better idea would be implementing a UPS, through either a battery, or supercapacitor. Make an update of KWH every minute or so, but have it sit in the volatile memory of the Arduino. When you detect that mains has failed and you're now running off auxiliary power, log the most recent KWH reading to the SD card, and then automatically cut power to the Arduino.
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You either have a seriously large installation, or are intent on aquiring a lot of junk data. You might be better off simply getting a meter that has isolated output pulses for your convenience, typically 1/10 kWh, and use Arduino for counting those.
I can't imagine that opening a meter up will reveal anything that you don't already know. They remember the last reading when the power fails with the same reliability as an old mechanical meter, and any inadequacy in this regard is likely to lead to some entertaining litigation.
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