adding data logging

[dave-in-nj]

I have a need to add data logging to a project. 

the ability to use a full on data logging shield is at the edge of the envelope.

however, it looks like I could either re-design the board and all the RTC and microSD card.  the flip side is to add pins for two add-on boards, a RTC and a SD card.

The re-designed SD card board
http://www.ebay.com/itm/200958993125?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

and one of the RTC boards
http://www.ebay.com/itm/2PCS-DS3231-AT24C32-IIC-precision-Real-time-clock-module-memory-module-Arduino-/310727159819? 

or some such.

Since I only need one in every 10 boards with the data logging, I am tossed.

suggestions ?

[Peter_n]

It depends on the board you have.
If it is an Arduino Uno, a click-on Adafruit Data Logger Shield is the best option.
https://www.adafruit.com/product/1141

When you want it really cheap, add connectors or soldering holes for those boards from Ebay.
The DS3231 module is for a rechargeable battery. If you want to use a normal battery, remove the diode.

There are clones of the Adafruit Data logger for 5 dollars.
http://www.ebay.com/sch/i.html?_sacat=0&LH_BIN=1&_nkw=data+logger+shield&_sop=15

[dave-in-nj]

I am making a custom board.  started with an ATTINY85, then an ATTINY84, but by the time I added a voltage regulator, it was easier to just get a NANO or mini.   I do not like the mini as it is not laid out to use a shield easily.   and lastly, the enclosure makes it very hard to use a shield.   ergo,  I am looking at either creating the pcb with all the components or making sort of back-plane and plugging in a NANO and a RTC and a SD card.

I have not read any discussions on the re-vamped MicroSD card boards.
http://www.ebay.com/itm/200958993125?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649


Probably have to get one and try it out.

[EKMallon]

I've had good luck so far with simple  ProMini/clone based loggers, with most of my builds drawing sleep currents around 0.3 mA (and I think most of that is the sleep current of the SD card itself - watch out for counterfeit cards)

http://edwardmallon.wordpress.com/2014/07/01/a-10-diy-data-logger-is-born/

With the BIG caveat that I still don't have a nice power-down method to protect the SD cards when the voltage falls below the minimum needed  by the voltage regulator . Posting that question to the playground today..

[fat16lib]

I've had good luck so far with simple  ProMini/clone based loggers, with most of my builds drawing sleep currents around 0.3 mA (and I think most of that is the sleep current of the SD card itself - watch out for counterfeit cards)

I did sleep current tests with two SanDisk cards here http://forum.arduino.cc/index.php?PHPSESSID=3qsj06ub17104c6v4c5mo4ehr1&topic=261021.msg1844372#msg1844372

The cards were an older SanDisk 1 GB SD and a new SanDisk 16 GB high end microSDHC.

The results:

I found that the cards went through at least two states.  The new card immediately drops to about 500 uamp then sleeps at about 70 uamp .  The old card immediately drops to about 200 uamp and sleeps at 60 uamp.

Since writes to the card only occur every 512 bytes, these cards mostly draw 60-70 micro-amps for slower data logging projects like your 3.3V system.

[EKMallon]

Then perhaps I still have not managed to locate genuine sandisk cards (and I probably have other power issues to sort out?) . My impression is that the sleeping sd cards come in around 200-240 micro amp. A few of the spec sheets I have found so far seemed to indicate that was ok.

But my original reason for posting was simply to mention that the SD cards can hang directly off the pins if the system is regulated. I simply solder onto one of the cheap adapter boards like these:

http://www.ebay.com/itm/171094703663?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

and they have a pretty small space footprint.

[fat16lib]

SanDisk claims some of their cards draw higher idle current in SPI mode if the unused pins are not pulled high.  I have not seen this on new cards.  I ground unused pins and maybe all that is important is they are not floating.

The 'RSV' pins are floating inputs. It is the responsibility of the host designer to connect external pullup resistors
to those lines. Otherwise non-expected high current consumption may occur due to the floating inputs.

Newer cards seem to have two levels of sleep. When idle for a second or two, they draw 200-500 micro-amps.  They then drop to 50-80 micro-amps.  I should do some tests to see how long it take for them to wake from each mode.