Wiring 1-Wire Devices
SUPPORTED 1-WIRE COMPONENTS
Please note that a short polling cycle with many temperature sensors will slow the bus communication down, so therefore the polling cycle should preferably stay at the default of 60 seconds. For this reason, a separate 1-wire extension is to be used for the access. Thus, no delays can occur during the access by the temperature sensors.
A characteristic of one wire sensors is how simple they are to use. However, please do pay attention to the following wiring instructions to ensure you get the optimum signal transfer for your sensor.
- When installing the sensor, use a cable with a cross-section of at least 0.6mm (we recommend using CAT7 Cable).
- We recommend a maximum of 20 sensors on one 1-Wire extension regardless of wiring topology.
- The following wiring instructions should be treated as a guide only. Depending on the environmental factors, including cable length and the number of sensors these instructions can vary.
We recommend you use data cable (Cat5e, Cat6 or Cat7), and you need to use one twisted pair for GND and data.
For longer distances or when running alongside mains cables use STP (shielded twisted pair) cable. DQ and GND should be connected using a twisted pair so the data signal is twisted against GND.
OPTIMAL WIRING TOPOLOGIES
Bus topology without branches is best suited for wiring. It allows a maximum range of 350m with a total of 20 sensors.
Bus topology with stubs
This topology can produce similar results to the bus topology without branches. The maximum cable length is slightly reduced to 300m when connecting 20 sensors.
FURTHER WIRING TOPOLOGIES
Bus topology with long stubs
One wire installation in bus topology with long stubs is not recommended as it reduces the maximum total cable length to 100m with 20 sensors.
Star topology is recommended only for small installations since all the sensors are brought together at one point. The maximum total cable length is 100m for 20 sensors.
Ring topology is not supported in one wire installations. If the sensors are connected in a ring, then no signals are received.
WIRING A 1-WIRE SENSOR
This is a schematic diagram for connecting the one wire temperature sensor DS18B20+. The pin assignments can vary between sensors so please refer to the manufacturer’s datasheet.
Parasitically powered: When wiring so the 1-Wire sensor is parasitic, GND and VDD are connected together and GND is connected to the extension. Ground and data should be twisted against each other.
Note that not all one wire sensors can be used with parasitic power supply wiring topology. Please refer to the manufacturer’s datasheet.
Separately powered: All three pins of the sensor should be connected to the Loxone 1-Wire extension. Ground and data should be twisted against each other.
1-Wire temperature sensors can be hidden behind switch plates due to their small size. It is important that the space behind is sealed though to prevent drafts and poor readings. Because you use a CAT cable to wire the 1-Wire sensors and switches the remaining cores can be used for the switch plate.
WIRING AN IBUTTON READER
The iButton reader is connected to the Loxone 1-Wire Extension. The white wire is wired to ‘DQ’ on the extension and the grey wire is wired to ‘GND’.
The yellow wire is the common ground for both LEDs. Green = Green LED, Red = Red LED. Both LEDs can be directly driven of 24V, we recommend to use digital outputs for this.
If you have purchased your iButton Reader before 2015, then no current limiting resistors are built into the product and the LEDs must be driven as follows.
Green LED: Operating voltage 2.1V, current 20mA
Red LED: Operating voltage 1.95V, current 20mA
If you are mounting the iButton outside, please remember to use a rainproof cap for the device as the iButton always have voltage flowing through the wiring and any water that gets into the wiring can cause issues and also the oxidation of the metal housing.
Since the iButton is the active component in the system, you can attach only one iButton reader for each 1-Wire Extension, if you want to tell which reader the signal was coming from. If you do not mind which reader the iButton has been identified at then you can attach as many readers as you wish to the 1-Wire extension. Maximum number of iButtons per reader is unlimited.
ADD IN 1-WIRE DEVICES
Select the 1-Wire Extension in the Periphery tree window, then click on ‘1-Wire Search’ in the Context tab on the top toolbar:
Select the sensor in the Search results and give it a name, then click on ‘Create device’. At this point you can also assign the iButton to a particular user, by selecting it from the drop down list and clicking ‘Assign to user’. Now this iButton serial number will be displayed in the user properties.
Do be aware that for iButtons – you must be pressing the button up against the reader for it to show in this search.
The sensor is displayed in the Periphery tree, and can now be used in the pages
IDENTIFYING 1-WIRE SENSORS
The easiest approach is to connect each sensor one after the other to avoid confusion. You can also connect all the sensors and then change the temperature of each sensor individually to identify it using Liveview.
If you do not find all the connected sensors in a 1-Wire search, this list should help in the analysis.
Before you go through the following points, make sure that the extension is online and the current program is running on the Miniserver.
- Make sure that there is no wire breaks or polarity reversals in your 1-wire cabling.
- If only parts of the wiring topology are found other parts of the cabling but not. Check the topology, taking into account the maximum cabling lengths and the cabling requirements.
- If no sensors are found, connect a sensor directly to the terminal of the extension and perform a new search.
- On 1-wire interface of the 1-Wire Extension you can measure the voltage values against GND.
- SET DQ to GND = 5V DC
- SOLL VDD to GND = 5V DC
- Measure different values by inserting the 3-pin plug on the top of the 1-Wire Extension and again measuring the voltage values directly on the extension pins as described in the previous section.
- Measure 5V in each case now, check your wiring for polarity reversals or wire breaks.
- If voltages <5V measured, check the voltage supply of the 1-Wire Extension.
If the problem persists, contact our support team.