I got the bathroom scale circuit logging data to an SD card tonight. The Adafruit logging shield came in handy again. I had to work through a number of issues; in particular, the sd card in the shield was dead, and I think that the RTC’s battery might be dead, too.
Anyway, I figured out how to create and append to files on the SD card.
There is something seriously wrong with the power situation on the circuit. Yet another example of my lack of knowledge of basic EE skills. Right now, the thing can only be powered from the USB port. The scale complains about low battery. I might switch the scale to use a wall wart.
I tried to figure out how to turn off the Arduino when not taking a reading, but that will involve some understanding of. Arduino interrupts, which I was not up for tonight. The scale itself stays powered all the time, probably in some kind of sleep mode while waiting for the user to step onto the scale.
I need to get the circuit installed onto some kind of permanent PCB. I am starting to lose track of all the wires.
So the scale is not quite ready for bathroom deployment. It is fully functional, but is too rickety for public consumption.