Data Logger Shield 3.3-4.0 V [SOLVED]

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markruys
 
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Joined: Sat Apr 13, 2013 2:30 pm

Data Logger Shield 3.3-4.0 V [SOLVED]

Post by markruys »

I use the Data Logger Shield to read out a TMP36. As suggested in http://learn.adafruit.com/adafruit-data ... ger-use-it, I took the 3.3 V from the shield. It gave me very erratic and instable temperature readings. Then I used the Arduino Uno's 3.3 V, and the readings were perfectly fine.

Without an SD card inserted, I measure 3.284 V, which is I guess all right (tough 5.3% below 3.3).
As soon as I insert an old 32 MB SD card, it fluctuates between 4.00 and 4.07 V.

Is this expected behaviour? That is, not to use the shield's 3.3V when a SD card is inserted?

I tested with an external 12 V adapter, and powered by USB, no difference. Also tested with 2 GB micro SD card, same results.
Last edited by markruys on Mon Apr 15, 2013 2:11 pm, edited 1 time in total.

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adafruit_support_bill
 
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Re: Data Logger Shield 3.3V

Post by adafruit_support_bill »

Definitely not expected behavior.
Without an SD card inserted, I measure 3.284 V, which is I guess all right (tough 5.3% below 3.3).
As soon as I insert an old 32 MB SD card, it fluctuates between 4.00 and 4.07 V.
Is your sketch reading or writing the SD card?

markruys
 
Posts: 3
Joined: Sat Apr 13, 2013 2:30 pm

Re: Data Logger Shield 3.3-4.0 V [SOLVED]

Post by markruys »

(ORIGINAL POST DELETED)

The problem was that I wired an LCD display to pins 11 and 12. This interferes with the SD card which needs these pins for the SPI interface.

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