EcoRenovator - View Single Post - DIY Data-Logger

AC_Hacker · 06-29-09, 12:57 PM

I have been working on my data logger and am happy to report that I now have a working unit and have been using it to do testing of hydronic floor ideas.

The log-o-matic board from Spark Fun had 8 A-to-D inputs and will digitize 8 voltage levels between 0 and 3.4 volts.

The first task was to build an interface board which consisted of a voltage divider with the thermistor being one of the resistors. The value of the fixed resistor was chosen to be about equal to the value of the thermistor, when the thermistor was at a temperature that was half-way between the range of values I expected to be measuring.

Here's the schematic:

I repeated this seven times on the interface board:

I also wanted one of the eight analog inputs to the data logger to measure power if I was testing a newly-built heat pump, for instance. I decided to use a toroid transformer, with the primary coil being the power line that conducted current to the heat pump. The secondary would then have a current induced into it that was proportional to current in the primary. Then I would rectify the AC and use a voltage divider to bring the voltage to a mid range between 1 an 3.4 volts.

It took several tries to do this... here's a photo of the secondary coil being wound on the toroid:

I forgot to photograph the primary winding. I used 14 ga. wire.

But here's a photo of the power-sender box:

Here's a photo of the working data-logger:

The data-logger isn't completely finished yet... it needs a case to protect it from accidents, but I'm using it so much, that may never happen.

So the data-logger writes files to a micro-SD card. When I hook up a USB to the data-logger, I'm able to download the data files and open them directly in Excel. This gives me access to a large set of data analysis and graphing tools.

My cost for the functioning data-logger is under $100. This includes log-o-matic board, thermistors, misc parts, etc. There was a large amount of time involved in putting it all together, but my understanding of data acquisition has increased substantially.

And it is a very useful tool.

Regards,

-AC_Hacker

06-29-09, 12:57 PM	#3
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Data-Logger, Good Progress... I have been working on my data logger and am happy to report that I now have a working unit and have been using it to do testing of hydronic floor ideas. The log-o-matic board from Spark Fun had 8 A-to-D inputs and will digitize 8 voltage levels between 0 and 3.4 volts. The first task was to build an interface board which consisted of a voltage divider with the thermistor being one of the resistors. The value of the fixed resistor was chosen to be about equal to the value of the thermistor, when the thermistor was at a temperature that was half-way between the range of values I expected to be measuring. Here's the schematic: I repeated this seven times on the interface board: I also wanted one of the eight analog inputs to the data logger to measure power if I was testing a newly-built heat pump, for instance. I decided to use a toroid transformer, with the primary coil being the power line that conducted current to the heat pump. The secondary would then have a current induced into it that was proportional to current in the primary. Then I would rectify the AC and use a voltage divider to bring the voltage to a mid range between 1 an 3.4 volts. It took several tries to do this... here's a photo of the secondary coil being wound on the toroid: I forgot to photograph the primary winding. I used 14 ga. wire. But here's a photo of the power-sender box: Here's a photo of the working data-logger: The data-logger isn't completely finished yet... it needs a case to protect it from accidents, but I'm using it so much, that may never happen. So the data-logger writes files to a micro-SD card. When I hook up a USB to the data-logger, I'm able to download the data files and open them directly in Excel. This gives me access to a large set of data analysis and graphing tools. My cost for the functioning data-logger is under $100. This includes log-o-matic board, thermistors, misc parts, etc. There was a large amount of time involved in putting it all together, but my understanding of data acquisition has increased substantially. And it is a very useful tool. Regards, -AC_Hacker Attached Images Last edited by AC_Hacker; 06-29-09 at 01:32 PM..