Level shifting 5v->3.3v

Hello there! I was trying to hook up SD card to my arduino duemillanove for last couple of days but without success. I found schematics from on the web using voltage dividers to level shift 5v from arduino to 3.3v. Instead of 10k and 4k7 resistors as described I used 1k and 470 resistors as I had them at home. I tried 3 different cards. With the old 16mb mmc I had problem with FAT12 filesystem as I don't know how to format it as fat16. Other 2 were microSD hooked through microSD to SD adapter formatted as FAT32. One of them was detected as type SD2 but filesystem could not be detected. So, I have a few questions: 1) Do resistors used in voltage dividing have to be, for some reason, same or similar to the ones originally used?

5V-470-1K-Gnd will work. Output level will be 5*1000/(470+1000) = 3.4V Current needed = 5/1470 = 3.4mA

What are you using for a power supply for 3.3V? Duemilanove only has 50mA from the FTDI chip, not enough to supply an SD card. Need 200-250mA for that.

I've cross posted non intentionally so if you could please move your reply to the right post and lock this one so no one else replies here. I've made such a mess, sorry once again :blush: Regarding your question. I did use 3.3v outlet. I wasn't avare that SD cards draw so much power :astonished: But, after realising that one of the wires I used was broken and was replaced, 3 of 4 micro SD cards were successfully read. Only 16mb mmc card failed.