T
Terry Pinnell
- Jan 1, 1970
- 0
I spent some hours today trying unsuccessfully to find the cause of my
burglar alarm being falsely triggered. But in the course of that I
came across a serious (not to say alarming) flaw. Each of my windows
and doors is protected by a N/C reed relay enclosed in a small
cylinder of plastic, mounted in the moving part, so as to be flush
against a similarly mounted permanent magnet in the fixed frame. When
the window is open, resistance across the reed goes from close to zero
to effectively infinite.
But one window switch was remaining at zero ohms. After several
minutes opening, closing and banging it, it then returned to normal
operation. As mentioned, these are fully enclosed magnets and reeds.
Obviously, this makes me apprehensive about reliability. I'd assumed
reed relays *must* open when the magnet was removed.
Anyone have any thoughts on possible cause please?
burglar alarm being falsely triggered. But in the course of that I
came across a serious (not to say alarming) flaw. Each of my windows
and doors is protected by a N/C reed relay enclosed in a small
cylinder of plastic, mounted in the moving part, so as to be flush
against a similarly mounted permanent magnet in the fixed frame. When
the window is open, resistance across the reed goes from close to zero
to effectively infinite.
But one window switch was remaining at zero ohms. After several
minutes opening, closing and banging it, it then returned to normal
operation. As mentioned, these are fully enclosed magnets and reeds.
Obviously, this makes me apprehensive about reliability. I'd assumed
reed relays *must* open when the magnet was removed.
Anyone have any thoughts on possible cause please?