Send a KNX command after a period without telegrams in Link’nX

The Presence detection function type in Link’nX monitors one or more KNX group addresses. When no telegram is received on them for the chosen duration, it sends a value to a target address.

Intended for administrators and installers who know the KNX addresses to monitor and the target command. Despite its name, the function does not by itself verify that a person is present or absent: choose the sources according to the known behavior of your equipment.

Before you start

• You know the source addresses to monitor, and the address, DPT and value of the target command.
• The timer is not accurate to the second. For an exact or very short delay, contact support before choosing this function.

Choose the source addresses

1. In Functions, click Add, fill in Function name and choose Presence detection in Function type. To edit an existing function, open its Edit pencil.
2. In Presence detection settings, under Sources, fill in Source address #1.
3. To monitor another address, click + Add and fill in the new row. The minus button on the right immediately removes a row from the form; it is disabled when only one source remains.

Set the timer and the command

In Timeout action sequence:

1. After If no value is received after, enter the timer in minutes, with the suffix min. Enter a positive duration: for example, 0.5 corresponds to 30 seconds and 2 to two minutes. These examples are fictitious and do not set the delay suited to your installation.
2. After Then send the value, fill in the timeout value. For a target of the DPT 1 family, the list offers 0 (false) and 1 (true); for a numeric target, enter the value suited to the command. The output values guide also covers the text case.
3. After To KNX address, fill in the target address, then its type in with DPT. The target DPT determines in particular how the value field is presented: reread the value after choosing it.

Format of the source and target addresses: three levels separated by slashes without spaces, from 0 to 31, then 0 to 7, then 0 to 255. Format of the target DPT: a main number from 1 to 999, a dot, then three or four digits. 1/2/3 and 1.001 are fictitious examples; use the parameters of the installation.

Understand the trigger

• A KNX write or response received on any of the sources restarts the timer, including when the value received is zero.
• A read request, without a value, does not restart it.
• If no new value is received during the period, the function requests the timeout value on the target. It does not repeat this command until new activity has rearmed the timer.
• The monitoring can result in a command even if no value has been received since the function was put into service.

Do not confuse the absence of telegrams with the reception of an absence value: a value received on a source, even zero, restarts the timer.

Save the function

1. Reread the Runtime interpretation. The preview shows the delay in ms, while the entry is in minutes: one minute corresponds to 60,000 ms. Also check the value, the destination and the Enabled or Disabled state.
2. Click Save, or Update for an existing function.

The functions guide explains the confirmations and disabling.

Check the result

After the confirmation, find the card in the Presence detection group and check Delay, Value to send, Sources and the state of the function.

Troubleshooting

Message	Action
Each source must be a valid KNX group address	Check all the source rows and remove empty additions
Timeout must be greater than 0	Enter a positive duration
Invalid KNX group address or Invalid DPT format	Check the target and its format

For an unknown parameter or an unexpected result after the checks in the function troubleshooting, contact support@can-nx.com with the context, the known settings and the tests already made.