EcoRenovator - View Single Post - DIY Data-Logger

AC_Hacker · 05-08-09, 11:43 AM

I've been looking through several threads and have noticed interest in tracking data, also an interest of mine for my heat pump developments.

I've looked to buy data-loggers and they can be expensive. Most that I have looked at start in at $300.

Here's a cute but typical example:

TR-72U Temp/Humidity Recorder (USB) Price:$297.00

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...nice looking product, but I was looking for a lot more functionality for a lot less money..

I did find an interesting unit ($60) at Spark Fun called the Logomatic:
SparkFun Electronics - Logomatic v2 Serial SD Datalogger

It's definitely a DIY thing. You get a tiny stuffed board that comes set up for 8 analog-to-digital channels (with micro-soldering 8 more are possible). The channels can also be configured to digital-to-analog and also digital in and out.

So the analog-to-digital channels will each read a variation in voltage from 0 to 3.5 volts and write the data to a micro SD card (user-supplied, 2 gig max), which can be read through a USB cable. The file structure is directly importable to Excel as a tab-delimited text file.

It is set up to be able to re-charge a Lithium-Polymer (AKA: LiPo) through USB and run off of that.

As it comes out of the box, it will not connect to USB and run at the same time. Running happens when only connected to battery and turned on

I bought 10 thermistors (thermally-variable resistors) to hook up to the analog-in lines. As it comes out of the box, it just writes values to the SD card, not temperatures.The ARM chip is capable of being programmed to make conversions on board, but at the present time I'm considering doing that on my PC, in Excel.

There's also a family of sensors called "1 wire" or "one wire" which actually require two or three wires, but a very large number of these can be controlled and read from and only need one I/O port.

I got 4 one wire thermometer units to experiment with. The attraction here is that compared to thermistors, they are more accurate, and do all their work within the chip, so stray voltage have little effect on them.

Another interesting item is a one wire humidity sensor that is capable of calculating dew point. I don't have one yet.

For my purposes, this unit will be ideal.

Most of the development work has been done,
the duration of most of my logging will be less than the time-to-exhaustion of the battery
A 2 Gig SD card will hold the data.

...But for longer logging periods this might not be the best logger. I have heard of another unit called the AVR Data Logger (AKA: Butterfly Data Logger):
Butterfly Data Logger - Google Search

This one has less power, a much lower current draw, and is reputed to be able to run for years on a coat-button sized Lithium battery.

Regards,

-AC_Hacker

05-08-09, 11:43 AM	#1
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	DIY Data-Logger I've been looking through several threads and have noticed interest in tracking data, also an interest of mine for my heat pump developments. I've looked to buy data-loggers and they can be expensive. Most that I have looked at start in at $300. Here's a cute but typical example: TR-72U Temp/Humidity Recorder (USB) Price:$297.00 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% ...nice looking product, but I was looking for a lot more functionality for a lot less money.. I did find an interesting unit ($60) at Spark Fun called the Logomatic: SparkFun Electronics - Logomatic v2 Serial SD Datalogger It's definitely a DIY thing. You get a tiny stuffed board that comes set up for 8 analog-to-digital channels (with micro-soldering 8 more are possible). The channels can also be configured to digital-to-analog and also digital in and out. So the analog-to-digital channels will each read a variation in voltage from 0 to 3.5 volts and write the data to a micro SD card (user-supplied, 2 gig max), which can be read through a USB cable. The file structure is directly importable to Excel as a tab-delimited text file. It is set up to be able to re-charge a Lithium-Polymer (AKA: LiPo) through USB and run off of that. As it comes out of the box, it will not connect to USB and run at the same time. Running happens when only connected to battery and turned on I bought 10 thermistors (thermally-variable resistors) to hook up to the analog-in lines. As it comes out of the box, it just writes values to the SD card, not temperatures.The ARM chip is capable of being programmed to make conversions on board, but at the present time I'm considering doing that on my PC, in Excel. There's also a family of sensors called "1 wire" or "one wire" which actually require two or three wires, but a very large number of these can be controlled and read from and only need one I/O port. I got 4 one wire thermometer units to experiment with. The attraction here is that compared to thermistors, they are more accurate, and do all their work within the chip, so stray voltage have little effect on them. Another interesting item is a one wire humidity sensor that is capable of calculating dew point. I don't have one yet. For my purposes, this unit will be ideal. Most of the development work has been done, the duration of most of my logging will be less than the time-to-exhaustion of the battery A 2 Gig SD card will hold the data. ...But for longer logging periods this might not be the best logger. I have heard of another unit called the AVR Data Logger (AKA: Butterfly Data Logger): Butterfly Data Logger - Google Search This one has less power, a much lower current draw, and is reputed to be able to run for years on a coat-button sized Lithium battery. Regards, -AC_Hacker Attached Images Last edited by AC_Hacker; 05-08-09 at 01:47 PM..