I need to connect multiple temperature sensors to my RPI. can you, please, elaborate whether/how can this be done with this or this unit? or can you suggest other unit?
I need to measure temp on the object and around the sensor.
Thanks!
4 Answers
There was not much documentation on the those sites (at least that I could read), so I am just giving you general information.
Most sensors that use I2C communication to talk to the pi, have the ability to select the devices address. This allows you to have two sensors that you can talk to separately.
If the device uses SPI communication, you would use one output pin on the pi for every device you connect. (this is the usually refereed to as the SS pin, 'software select')
sensors that use the dallas 1wire protocol also use addressing, usually hard coded I think( like a serial number)
If you need to use devices that do no have any way to address them (this would be rare I think) There is still options. You can control the power to the sensor using a relay or fet. This would allow you(your software) to know which sensor is powered, so if you take a reading from one, and then un-power the first sensor, power the second one and take a reading from sensor 2. Again this is rare and does require understanding the sensor to know how long it has to be powered before the reading is reliable.
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there is link on those sites to sheets: first: elecrow.com/wiki/… second: waveshare.com/wiki/Infrared_Temperature_Sensor and yeah, I need something like Dallas 1Wire, strange I cannot find any ir thermometer based on that protocol Commented May 12, 2020 at 14:31
There is not enough information about the first sensor. I do not see any mention of the interface used.
The second sensor uses I2C so that it can be connected to the Pi's I2C bus.
I see no way of changing the second sensor's I2C address. That means that if you want to connect more than one you will need
- to use an I2C multiplexor chip as well
- or use one additional software I2C bus per sensor added to the Pi.
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1The first sensor's picture shows a 4 pin connector with partial visibility of board labels. I guess that "ND" is GND (ground) and "CL" is SCL (I2C clock). I would not buy either of these without verifying that they are I2C and have a method to set a device address so multiple sensors can be connected to one I2C bus. Commented May 15, 2020 at 6:00
Most practical by multi temperature sensors are the DS18b20 1-wire types. On one GPIO you can connect many sensors and for most program languages are libraries available.
Both sensors seem to be I2C ones. Here are some guides for you to start thinkering: https://learn.adafruit.com/circuitpython-on-orangepi-linux/i2c-sensors-and-devices and https://learn.adafruit.com/working-with-i2c-devices .
Maybe (just a guess) the vendor you posted the link of may have a tutorials/guides page that you can search into?