Is it possible to read digital temperature sensors with a PiFace?

Well if you're happy wielding a soldering iron, you can always add some extra connections.

Be aware though, that DHT11 doesn't appear to be I2C device, so you'll need some dedicated GPIO's for it. A quick search didn't turn up any schematics for the pi-face, so no idea if there's any free.

It will normally be ok to share i2c among multiple devices as long as they all run at the same voltage and don't have conflicting addresses (and level shifters are available for any 5v devices).

There's also some equivalent i2c humidity/temperature sensors available such as the Sensiron SHT21 and Honeywell Humidicon HIH6130 that you could use in place of the DHT11, although these will likely cost more.

It's a bit frustrating that PiFace doesn't provide schematics for the board in a convenient and accessible place. As far as I can tell, PiFace uses the SPI bus only and leaves most of the other GPIOs untouched but without a schematic, it's hard to be sure.

PiFace needs to fix this IMHO.

I did think it was a bit odd for something produced for education by an educational institution to be lacking schematics. Most everyone else has realised that you need them for anything even remotely useful.

Hi there, are there any updates on this? I'd like like to know if there are any others solutions or workarounds.

In my case I'd need two sensors connected and what I have a PiFace board connected to my raspberry pi board.

Looking forward,

Alex

Well as the PiFace only uses the SPI pins, you're free to use any of the rest. You just need to sort yourself some method to connect to them.

selsinork: Have you managed to connect at least one temperature sensor? I'm not sure if I can connect two of them. Thanks!

Piface Digital schematic is available here

http://pifacedigital.wordpress.com/2012/05/02/kernel-driver-delays-and-new-interface-board/

Unforunately, you'll need to be handy with a soldering iron to add connections onto the GPIO connections, as the PiFace socket doesn't extend through.

You can either remove the existing one and replace with one that has the longer pins or,

I used two single strips soldered carefully onto the top of the GPIO connector.

Solder the one closest to the relays first, and then when you're happy with that, solder the other on.

There is a link for reading a DS18B20 using GPIO #4

http://www.element14.com/community/groups/raspberry-pi/blog/2012/07/26/is-it-done-yet-temperature-sensing-with-the-raspberry-pi#comment-16221

Adafruit has one at

http://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing

This link shows the functions etc of the GPIO and is less confusing than some others.(imo)

http://elinux.org/RPi_Low-level_peripherals#General_Purpose_Input.2FOutput_.28GPIO.29

Cheers

Mark

Alex Szilagyi wrote:

 

selsinork: Have you managed to connect at least one temperature sensor? I'm not sure if I can connect two of them. Thanks!

I'm not using a PiFace myself, just directly connecting to the GPIO header.

I have three mcp9803 temperature sensors, a humidity sensor and a barometric pressure sensor all connected to the I2C bus, you just need to follow the stuff in the link Mark posted and configure all of your I2C devices with different addresses. The mcp9803's I'm using have three address lines, so you can connect up to eight of them. Although it does depend slightly on what other things you connect as it's always possible to have an address conflict due to the limited number of addresses available.

I'd be interested to know if you have suggestions on how to use the sensor as part of a trigger for a solenoid? For example, at 500m (altitude) I'd like to activate a solenoid. Yes, I am an amateur...

Shouldn't be too hard, there are formula to convert pressure into altitude. So read the sensor, evaluate the formula and if the result has passed 500m you set a GPIO to activate the solenoid.