Array of Temperature sensors

NETMF & Gadgeteer
1

Hi,

I need to monitor temperature in a room where I will tie various temperature sensors to a cable that hangs from a roof. I would like to know if it is possible to read multiple sensors in array format all plugging into one “slot” on the fez spider II board. It simply would not work to have 100 sensors each plugging to its own slot - that way I will require multiple fez II boards.

Any advice or codes samples please…?

Riaan

2

One-Wire DS18B20

2 Likes
3

I have had success with these: [url]https://www.amazon.com/Gikfun-DS18B20-Temperature-Waterproof-Arduino/dp/B00Q9YBIJI/ref=sr_1_2?ie=UTF8&qid=1469805162&sr=8-2&keywords=ds18b20[/url]
which are based on the Dallas “1-wire” sensor.[url]https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf[/url]

Quite a few can be connected to 1 socket and the wirelength can be relatively long (search the internet for more details).

Code can be found here: [url]https://www.ghielectronics.com/community/codeshare/entry/325[/url]
or here: [url]https://bitbucket.org/StablePoint/stablepoint.hardware.onewire/wiki/Home[/url]

4

@ riaan.mastenbroek@ gmail.com -
I have found this library to be extremely helpful, as I read over 250 sensors per board, (although using 8 pins, and a 5v level shifter, because there is a very small range of voltages that can cause the DS18b20 to provide inaccurate readings).
*Note, not sure if its been fixed since I downloaded it, but there was a bug with negative Celcius temperatures.

https://bitbucket.org/StablePoint/stablepoint.hardware.onewire/wiki/Home

Depending on how far apart the sensors are, you are limited to the number of sensors per string by the total capacitance of the string. If I remember correctly, its approximately 100pf per string. In my experience, this means that you need to pay very close attention to the wire you use to connect the sensors together.

If you are in normal room temperature ranges, two companies that already make cables that you are describing would be OPIsystems/Integris, and Intelliair.

There are also thermocouple solutions for wider temperature ranges, but they quickly get very complex.

5

DS18B20+ sensors are quite inexpensive, <$3 in ones from Digi-Key in an easy-to-solder through-hole package.