Posts: 1
Joined: Thu Oct 03, 2013 2:12 pm

Looking for suggestions for multi-sensor project

Thu Oct 03, 2013 2:36 pm


I need to create a pair of sensing and logging devices to capture metrics. The wish list is to have the following sensors (note, any temp sensors where the approximate temp is not specified are to be in the range of 0 degrees to 150 degrees Fahrenheit)
  • Air Humidity
  • Air Temp (x4 of these, one of which would be outside)
  • Air temp (hot. Approx 400 degrees F)
  • Surface temperature
  • Lumens Sensor -or- sense voltage off solar cell
  • Wind Speed and direction
  • Input power on a 220V appliance (need to derive killowatts, run time, and count cycles)
I'm looking to log this data, ideally every second, to a database with a time/date stamp.

I have numerous Raspberry Pis I use for computing and as appliances but I've not yet done anything with external boards or sensors. I'm not sure where to start with that. Any suggestions on boards, packages, sensors, etc that anyone can make would be highly appreciated. I see there are numerous options but I don't know the gotchas or maximums amongst them.

Posts: 4
Joined: Wed May 08, 2013 5:00 am

Re: Looking for suggestions for multi-sensor project

Sat Oct 05, 2013 7:35 am

You can look at the side of http://www.lcjcapteurs.com/?lang=en. vane and anemometer easy to use. it uses ASCII serial connection, such as a GPS.

Posts: 3172
Joined: Sat Aug 18, 2012 1:21 am
Location: Korea

Re: Looking for suggestions for multi-sensor project

Sat Oct 05, 2013 8:36 am

Hi there,

For ambient temperatures take a look at the DS1820 family. These are one-wire devices, so you can make a small network with several of them connected to the same twisted-pair wire. This would cover your air-temp x4. Put the outside one under an upturned white plastic bowl to keep the rain and sun off.

What is the range of 'surface temperature'? The DS1820 has a range of about -55°C to +125°C.

This leads on to the hot air temperature. 400°F is about 200°C, so it's out of range. I suggest you take a look at thermocouples. Here's a fairly detailed article covering the theory and practical implementation:
http://www.analog.com/library/analogdia ... ouple.html

Humidity sensing (and temperature) is discussed here:
http://www.raspberrypi.org/phpBB3/viewt ... 63&t=47391

Lumens sensing could probably be done with a LDR (light-dependent resistor) with an ADC. If you are lucky you can use a single ADC chip with several inputs for your other sensors.

Windspeed and direction has been covered above, so you're left with the 220V device monitor, which needs a little more explanation. If it's an external system that you are monitoring (not controlling) then perhaps there is a pilot lamp or LED the lights up when it is operating? You can hook up a photodiode to detect if the lamp is on or off, and determine that the device is running or not.

It sounds like you are monitoring a furnace or heater somewhere. This is a common project and you'll find lots of writeups on the net. I suggest you also search for Arduino projects for more ideas, since Arduino is another thing that people like to connect sensors to. Anything that works with Arduino can be made to work with the Pi (the first 'gotcha' being that the Pi's GPIOs work at 3V3, not 5V though).

Oh! This just in...
http://www.maximintegrated.com/datashee ... vp/id/7953

Google for other 'one-wire' sensors and chips.

Good luck!

Return to “Automation, sensing and robotics”