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Topic: A really inexpensive data logger with only three components. (Read 5243 times) previous topic - next topic

Nick Gammon

Please, the labelling of the six pins in the SD card adapter am using is quite different, there is no MOSI, MISO and SPCLK, just a bunch of things I dont understand. I need help
Please start a new thread. This is nothing to do with showing off your project. Also state what adapter you have and what labels you see (photo).
Please post technical questions on the forum, not by personal message. Thanks!

More info:


May 07, 2015, 05:32 pm Last Edit: May 07, 2015, 05:42 pm by EKMallon Reason: formatting
Apologies for the confusing labeling, (and the late reply)

Without knowing any better, I used the same numbering as the examples shown at http://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf

The SD card adapter I am currently using is a "microSD card adapter for Raspberry Pi" from Adafruit. But there are many other options available, and I provided links to several of them at the bottom of the post with the schematic at:


I have found that some boards conduct heat to the pads holding spring pins much faster than others, which means if you linger while soldering, and hear a "snap" then you probably need to start over with a new board. Also, I have sometimes have very fine solder hairs bridging the contacts, which prevents the sd card from working. So I inspect the springs, and the jumper wires on the back of raspberry pi card adapter very carefully before connecting to the Arduino. It's also really easy to get the connections switched around, so I always use different colored wires for each SPI line

Attached is the back side of the Adafruit adapter, next to my schematic. With the numbering I used:

1 = Chip Select
2 = Data in = MOSI
3 = GND
4 = VDD  (supply voltage, not over 3.3v)
5 = SCLK
6 = GND
7 = Data out = MISO

8&9 are not used, but are pulled up to VDD with a resistor from 20-50K ohm because I found that some  SD cards drew much more sleep current if those pins were left floating.


And apologies to the thread in general if the housing photos were out of place.  In my head, the weather proof housing is a necessary part of building a datalogger.  I was just happy to finally have one that could be made with so few fabrication steps.  

Also the space limitations of the 2" pipe design lead me to put the components in a dramatically different physical configuration than the builds I posted about in 2014, and this taught me some lessons that are not in the schematic.  For example, flipping the RTC board over makes it much easier to change the backup battery after the unit has been running for a while.

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