Temperature data logging

[Mike AA]

We have recently been asked to make a device to read temperatures of soil at increments of 1ft for 20ft logged hourly in a remote location over the course of the up coming winter months in sw Michigan. We will be using temperature probes with 2 conductor wiring for the temperature readouts, thats 21 probes we will be connecting, thats the easy part. The difficulty we have is what device (c-rio is a bit expensive to leave in the elements unmonitored) could we use with this many inputs. The data would have to be stored for upwards of 30 days at a time and the device relatively low power draw, solar panels will provide power for charging batteries and powering the device. Would something like an Aruindo work for this application with a breakout board? Could it save the data to a text file for later reading and not erase with a power loss?

Thanks for any help and suggestions!
Team 3458 Code Blue

[Jim Wilks]

What are you using for temperature probes?

[billbo911]

If you can use a sensor like this one (https://www.sparkfun.com/products/9418), an Arduino should work great.
Using the I2C libraries, you should be able to access all 21 sensors quite easily.

[sanddrag]

Have you considered transmitting over APRS? This would let you see the data in real time, and log it remotely. You'd need an amateur radio license though (which is not hard to get).

[EricVanWyk]

If you can use a sensor like this one (https://www.sparkfun.com/products/9418), an Arduino should work great.
Using the I2C libraries, you should be able to access all 21 sensors quite easily.

20 feet is pretty long for I2C. If you use this part, be careful with your cabling. If it doesn't work, slow down your data rate, fiddle with the pull up resistors, and possibly use a repeater.

[Mike AA]

The probes we are using will likely be the style used in outdoor remote thermometers which have long leads to tie into.

Billbo, that would work in air just fine but we will be forcing these sensors into a silt soil. The plan was to attach them to the side of a pipe/tube that we could press into the ground the conductors would run within the pipe but the sensors would be on stand-offs on the side of the pipe. The sensors need to be in direct contact with the soil, or as best as we can get.

The purpose of the logging is that we dont have to monitor 24/7 and the guy who is doing the monitoring doesnt have the time (or patience unfortunately) to frequently check the equipment. We are measuring 21 sensors 24hrs a day and approximately 150days.

[Lisa Perez]

How remote is "remote"? If you'll be using an Arduino outside, using an XBee shield for communication to an Arduino inside somewhere might be an option, but it really depends how remote the sensors are and what exactly is in between the 2 Arduinos (besides the soil).

[Kyle R]

If you are going to use analog temperature sensors you can just use a multiplexer (https://www.sparkfun.com/products/299) and run them all into an Arduino. Then you can add on whatever method of communication suits your needs.

[Gdeaver]

You may want to consider a Maxim one wire temperature sensor like the DS18B20. In the multi-drop configuration only 3 wires are needed. 3.0 -5 volt, ground, and signal. Only one processor pin is needed. The one wire protocol is complicated but libraries are available for many processors. 750 ms for a sample but you do not need speed. Accuracy can be improved by calibration. The to-92 package lends it's self to directly soldering wires to the leads and insulating and then pot the unit in a metal tube. Use high quality wire. Be sure to insulate and water proof well. The micro controller is not going to keep time well in an out door temperature environment. May want to add a real time clock with a real good TCO. If it had a timer interrupt, it could wake the processor from sleep and do the sampling then go back to sleep. Maxim does have one wire real time clocks that with the proper TCXO could work. Some where on their web site there is an app note on real time clocks and oscillators for wide temperature extremes. Check the operating temperature of all electronics used. Many do not work well at low temps. Atmel serial data flash works well for data logging in harsh conditions. Digi does make xbee modules That have very long ranges with high gain antennas. Once again the are allot of libraries for the xbee stuff. Don't for get to turn the power off to the sensors to save power. What battery works well at -20F? With this data you could answer the question of 'how deep do I have to bury the horizontal geothermal heat exchange pipes in this area. Mine are at 14'.

[Hugh Meyer]

Mike,

What is your sample rate going to be?

This device is a good way to log to a SD card. It has several types of inputs. I have used it successfully for several years now to monitor water levels in a sump pump pit.

https://www.sparkfun.com/products/10216

This is a nice processor board that I use in the same system.

https://www.olimex.com/Products/PIC/Development/PIC-MAXI-WEB/

Sounds like a fun project.

-Hugh

[Mike AA]

Lisa, remote is no power for a good half mile or more and no communications other than cellular service for further than that. The guy who will be checking lives about 5 miles away. The Control device will be sitting above ground in a protected case similar to a plastic toolbox.

Kyle, I like the idea of the multiplexer, it only has 16 channels but with only 4 ports to use I can easily use 2 of them to read all 21 sensors and sparkfun already has them on breakout boards. You item link got me thinking and I found an item from digikey that has 32 channels so I don't need to try to read from 2 different multiplexers. Thanks!

Gdeaver, I found a tutorial about using the maxim DS18B20 connected to an aruindo and a program to read the value so if I use it I am already partway there in programming too! Thanks!

[Mike AA]

Hugh,

My samples rate I guess would only need to be once per hour per sensor so VERY slow rate.

What kind of device are you using for the actual measurement? Do you use the processor for taking the info and sending to a webpage/email to notify you of issues?

I am a little inexperienced in programming new items other than the c-Rio, old IFI controller and the old basic stamp/basic controllers. And just getting into using new types of sensors and serial interfaces. I would really like to use the sensor Gdeaver mentioned the Maxim DS18B20 which if I am reading right uses a serial bus so I can connect more than 1 to one port of a micro controller. Similar to how the Jaguar can connect with CAN. The Logomatic seems to be able to do all the logging exactly what I need but I am somewhat unsure if I will still need another micro controller like the aruindo or your processor to read the ports or if I can just use the multiplexer tied right to the Logomatic.


Mike,

What is your sample rate going to be?

This device is a good way to log to a SD card. It has several types of inputs. I have used it successfully for several years now to monitor water levels in a sump pump pit.

https://www.sparkfun.com/products/10216

This is a nice processor board that I use in the same system.

https://www.olimex.com/Products/PIC/Development/PIC-MAXI-WEB/

Sounds like a fun project.

-Hugh

[dbarr4011]

Mike

I am one of the mentors for Team 141 helping with programming and controls. If you have a chance give me a call and we can review your project. I have a small contract engineering company and we may have some parts that would help with this application. For this application we need to look at the temperature range, power for the monitoring system, data storage requirements, sensor requirements.
David Barr
Suntec Services
616-335-3755
616-566-1150 Cell

[Hugh Meyer]

Mike,

You could do any of the options you listed. I think the simplest would be to use the multiplexer into the logomatic card. It depends on how you want to log and keep the time. If you want real time of day information logged, then you need a clock. That is why I see you needing another processor. You will need to set the clock...or you could set up a cheap GPS receiver to get the time of day. That is a simple serial data stream that would have TOD information and be very precise. Sparkfun has several modules that could do that.

Yes, my application has a website that shows the real time data and the data is also logged to the MicroSD card. The maxiweb board is a PIC, which is just like programming the old IFI controller...it even uses MPLAB. If you want the URL PM me and I will forward it to you. I don't really want to post it here on a public site. It might be overkill for your project since it supports a http server and network connections. I use several conductive rods set to different depth to indicate water level.

You should be OK programming. If you can do the IFI and the cRIO then you can do any of the kits mentioned in this thread.

-Hugh

[Mike AA]

I ended up buying a logomatic v2 from sparkfun from Hugh's link above. I also ordered the ds18b20 thermometers. I understand how to interface now but i have no idea what program i should use to program a program into the data logger if i even need to. I am almost thinking i need to use a program like winARM since this is an arm processor but i dont know if i even need to program the logger or just put the probes on and power it up.

Help, please?