Hi
folks, i have bought an optico isolated relay board for a project.The relay is going to wired to thermostat.I done majority of the work.What is left now is how to wire the alarm.I want the alarm to sound when tempereture rises too high or goes too low and when there is power failure.
The problem is the alarm uses 12VDC (it runs on car battery)whilst the output of relay board (fitted with general purpose relay)is 240VAC.I am the 240VAC will damage the alarm .I have seen this type of thing work somewhere else some years back.I heard it is called 'battery backed control circuit'.
I do not know how wire to leads and whether to use 'NC' or 'NO' contacts.
Any questions welcome!
folks, i have bought an optico isolated relay board for a project.The relay is going to wired to thermostat.I done majority of the work.What is left now is how to wire the alarm.I want the alarm to sound when tempereture rises too high or goes too low and when there is power failure.
The problem is the alarm uses 12VDC (it runs on car battery)whilst the output of relay board (fitted with general purpose relay)is 240VAC.I am the 240VAC will damage the alarm .I have seen this type of thing work somewhere else some years back.I heard it is called 'battery backed control circuit'.
I do not know how wire to leads and whether to use 'NC' or 'NO' contacts.
Any questions welcome!
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