Generally, if we purchase 2 identical sensors, they will have identical addresses, so we can only use 1 of these at a time. Some models might require reprogramming the module to change the address, which isn't practical. But other sensors sometimes offer simple ways to set the address.
For example, from Supported Sensors and Inputs, a few temp sensors that are integrated are:
- Digital Matter Temperature Probe
- This sensor can be given 1 of 2 unique addresses by connecting the green wire to either 3V3 or GND (see Falcon - Wiring in DM I2C Sensors) So we can use 2 of these at once
- Digital Matter Temp/Hum Sensor
- This sensor has 1 fixed address, so we can only use 1 at a time
- TMP117 Temp Sensor
- This temp sensor (comes as a chip) - can be given 1 of 4 addresses by jumping pins on the module. So we can use 4 at a time
Equally we could use all of these together, i.e. 2 x Temp Probes + 1 x Temp/Hum Sensor + 4 x TMP117. Given all 7 have unique I2C addresses.
Other Limitations
While we can theoretically be connecting up to 128 sensors to a Falcon, we run into some other limitations that mean in practice we wouldn't really do this.
- I2C stands for Inter-Integrated Circuit - it was designed for low speed communication between components on a circuit board. So it does not work well for long cable runs over a few metres
- Simply attaching lots of sensors is going to become impractical
- There are only 14 available analogue data fields currently on the device to store any sensor readings. So 14 is our upper limit. However if we are approaching this we should consider BLE sensor options.
When both external power and batteries are installed, the device will use whatever is supplying the higher voltage.
This will prevent set such as installing 3 x LTC batteries (giving ~11.5V) in conjunction with a 5V external supply. The batteries will always be used in this configuration
When external and battery supplies are used, if there is a power cut, we swap over to batteries, and some capacity is used until external power is restored.
For a list of currently integrated sensors, see Supported Sensors and Inputs. If you require another sensor, or wish to use your own, the Falcon has an I2C input and 2 x Analogue 0-30V inputs for sensors.
Analogue Sensors
Analogue sensors simply work by outputting a voltage based on the sensor value. For example it might output between 2-10V. For a temp sensor 2V might represent 10°C and 10V = 150°C. So then we can work out the scaling and know what voltage corresponds to what temperate. The Falcon simply reads the voltage, and we do the conversion on the server easily. So any analogue sensor will work with the Falcon, without any integration. We generally only need to consider how we will power the sensor. If we are running off battery power alone, we can only power the sensor by connecting it to the 3V3 output on the Falcon - which will be turned on to power the sensor when we need to take a reading. If your sensor requires a higher voltage it will need to be powered externally - or consider using the Eagle.I2C Sensors
I2C is simply a low level communication interface. Each new sensor generally needs to be integrated in FW. Sensors should be able to be powered by 3.3V ideally - so that it can be connected directly to the Falcon for power rather than externally powered. Speak to us about integration into device FW - fees may apply.