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+--- Thread: KC868-A8 - question regarding safety shutdown (/showthread.php?tid=3182)
KC868-A8 - question regarding safety shutdown - Karle - 08-21-2023
Hi !
I think about buying the KC868-A8 module for controlling my heating system by external signals.
The KC868-A8 board shall be connected via ethernet to my home assistant device which will control the board (switching relais to control the temperature, set heating or cooling mode and so on).
This is clear so far and I think this can be done relatively easily.
What is not clear for me at the moment:
How does the KC868-A8 board react ....
... if home assistant freezes or the ethernet connection is gone ?
... if there is a power loss and power comes back ?
Does it go always to the state "all relays" off -> which would mean a safe state in my case ?
Is there a way to supervise the board or turn off all relais in case of any failure coming from home assistant ?
Is there a way to control the proper functioning of the board itself respectively the relais ?
With the 8 relais I only want to switch "signals" no "load" -> Are this relais suitable for this purpose ?
For how many switching cycles are the relais designed ?
Thank you for your feedback.
Greets Karl
RE: KC868-A8 - question regarding safety shutdown - admin - 08-21-2023
... if home assistant freezes or the ethernet connection is gone ?
--> digital input connect with manaul control button, if without network, also is work locally.
... if there is a power loss and power comes back ?
Does it go always to the state "all relays" off -> which would mean a safe state in my case ?
--> this can set by esphome,whether use remember relay function.
Is there a way to supervise the board or turn off all relais in case of any failure coming from home assistant ?
--> suggest set your digital input port to turn off relay relaies.
Is there a way to control the proper functioning of the board itself respectively the relais ?
--> as same as last quesiton.
With the 8 relais I only want to switch "signals" no "load" -> Are this relais suitable for this purpose ?
--> sure, "signal" just low current. it can use by relay.
For how many switching cycles are the relais designed ?
--> how many frequency you want to use? relay is physical, suggest wait 200ms for ON/OFF delay time. this you can test.
RE: KC868-A8 - question regarding safety shutdown - Karle - 08-22-2023
Thank you for your feedback.
Some of your hints already helped.
But I will ask some more precise questions:
To control locally with buttons is clear. But what does the board do if the Lan connection is gone. Do the relais and states just stay as they are or ist there also a way to shut all relais down ?
What do you mean by use a digital input to turn off all relais (where should the signal come from)? How could that be realized?
My idea could be to built something like a watchdog -> for example send e.g. every 5 seconds a "ping" to the KC868 board. And if this "ping" is not there the board shuts down all relais. Is that possible (maybe also via ethernet) ? Perhaps the same could be done the other way round.
My goal is to have some safety, that all relais go off in an "unplanned" event like connection loss, freezes and so on.
My cycle frequency will be very low, which means I only want to switch every few minutes. My question was about the design life of the relais (e.g. 100k cycles).
Thank you for your support.
Greets Karl
RE: KC868-A8 - question regarding safety shutdown - admin - 08-22-2023
1. But what does the board do if the Lan connection is gone. Do the relais and states just stay as they are or ist there also a way to shut all relais down ?
-->relais and states just stay as they are, no changes, will not all off.
2. What do you mean by use a digital input to turn off all relais (where should the signal come from)? How could that be realized?
--> my means, digital input can connect with push button, define any fucntion you wanted.
3. My idea could be to built something like a watchdog -> for example send e.g. every 5 seconds a "ping" to the KC868 board. And if this "ping" is not there the board shuts down all relais. Is that possible (maybe also via ethernet) ? Perhaps the same could be done the other way round.
--> do you want auto turn all relay off when network disconnected?
4. My idea could be to built something like a watchdog -> for example send e.g. every 5 seconds a "ping" to the KC868 board. And if this "ping" is not there the board shuts down all relais. Is that possible (maybe also via ethernet) ? Perhaps the same could be done the other way round.
--> what software you will use? home assistant? if you have a server, you can do that.
RE: KC868-A8 - question regarding safety shutdown - Karle - 08-22-2023
Yes I want to use home assistant for controlling the relais on the board (based on a odroid system).
I want to use a thermostat and temperature sensors connected to HA to control the relais board (in the end temperature regulation). This system is already there and can be used.
So connecting temperature sensors directly to the ESP32 board is very difficult.
All problems related to the temperature sensors (e.g. one is defect) can be solved on HA side.
But for any case of failure like e.g. connection loss of ethernet, freeze of home assistant) I want to automatically switch all relays off to be in a safe state.
This is only relevant for the case, that nobody is at home, that the system does not do anything which could lead to problems.
So there needs to be some error handling.
RE: KC868-A8 - question regarding safety shutdown - admin - 08-22-2023
i think you can write a script in home assistant to detect board whether is online, then auto turn off all relaies.