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Topic: SD card won't initialize, Voltage increases after card is connected (Read 1 time) previous topic - next topic

nkaati

I can't seem to figure out why my SD card won't initialize.  I checking the voltage and after the SD card is connected the voltage rises from 3.3 to 3.6V and then 500ms later jumps to 3.9V.
I'm using the 3.3V pin from the Arduino Duemilanove.  Is this normal that the voltage would increase after plugging in the SD card.  I don't think the pins I'm using for the SPI connection are incorrect.

Thanks,
Nathan

CrossRoads

The 3.3V pin only puts out 50mA from the FTDI USB chip; you are overstressing it, and may notice it getting hot. You will need another source that can supply more current.
My card here has a regulator just to provide current to the SD card.
http://www.crossroadsfencing.com/BobuinoRev17
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

nkaati

Even using an alternative source I'm still getting an increase in voltage after plugging in the sd card.
it jumps from 3.3V to 3.5V and the supply is 100mA.

Still doesn't recognize the sd card

PaulS

Time to post a schematic showing how the SD card is wired.

nkaati

Here is a picture of the pin connections, I only changed the CS pin from 4 to 10 compared to the examples. All the jumpers are on DIS(abled).

nkaati

Are these connections correct, I'm still not sure why there would be an increase in voltage.

CrossRoads

Are you driving it from Arduino pins directly? Or do you have a 3.3V level shifter for SCK, SS, and MOSI?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

nkaati

There are voltage dividing resistors to drop the output voltage from the pins down to 3.3V on the pcb.

Grumpy_Mike

So what are the values? It sounds like these signals are back powering your card. This is not good.
Using resistors is a poor way of driving a card and some cards won't work with this method.

CrossRoads

I see some jumpers there - would seem to need them set on the  SS, MISO, MOSI, SCK side to work with SPI.
Is there a schematic for that card?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

nkaati

Well when I originally had it on a breadboard I had the SD card running for 12 hour periods at a time from the Arduino Duemilanove and I've done that multiple times about 20 times. Never had a problem until I took it off the breadboard.  Yes there is a pdf of the schematic of the board and uses for SD and SPI modes.  I've had the jumpers on DIS, because of there connection to 3.3V.


There are voltage dividing resistors to drop the output voltage from the pins down to 3.3V on the pcb.


I've had a closer look at the pdf and I think I take back what I said.
I'd like to know how I had it working in the first place :|
The voltages on the breadboard were fine when first using the SD card slot and interface with the arduino.


CrossRoads

Just lucky I guess? Page 3 shows a level shifting chip when connected to a 5V uC.
You haven't fried your SPI pins? They still drive hi/lo okay?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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