Monday, 21 January 2013

SD cards and 3.3v

So it seems that whilst the SD card reader I ordered from China *says* that it will work with 5v or 3.3v it doesn't actually have the necessary circuitry to drop the 5v signals down to 3.3v. This means that there is a very good chance it will damage any SD card put in it if run from 5v.

I have a couple of options:
  1. Ignore it and hope 5v won't blow my SD card up
  2. Build some level shifting circuitry to drop the 5v signals down to 3.3v
  3. Buy an existing Arduino shield with a SD card reader and that circuity built in.
No, I can can make my own (option 2) and there are instructions online from someone else on how to do this. But to be honest that kind of sounds like too much work. Well, I'm not afraid of work per se, but there is an expression in the IT world called Yak Shaving and this is apt here.

Actually, Adafruit make a quite nice Datalogger Shield which contains both a SD card reader (and level shifter) and also a Realtime Clock. It also has a prototyping area on there on which I could put the voltage/current sensors and the temperature sensor.

This would increase the cost of the project a little bit (maybe about £10) but would mean a lot more of the system is pre-assembled and would make it much easier for others to replicate.

This actually means I could get all of my circuitry I need for this project on a single shield, which could then be put on top of any Arduino (ie. an official 'full fat' Arduino or a bare-bones one such as the Xino Basic that I plan to use.

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