Re: Re: motion detectors: need some input

[Kevin Hawkins <lists@xxxxxxxxxxxxxxxxx>]

Tom Van den Panhuyzen wrote:

>Hi Kevin,
>
>On Tue, 11 Jan 2005 01:45:14 +0000, Kevin Hawkins
><lists@xxxxxxx> wrote:
>
>
>>Tom Van den Panhuyzen wrote:
>>Most PIR's don't usually generate a voltage - they are usually like
a
>>switch in that they 'connect' whatever you feed in to their output
when
>>they are triggered (or possibly the reverse, removing the signal
when
>>triggered). hence if you feed 230V in then 230V comes out.. The
>>'contacts' have to be rated to handle the voltage in use and to
carry
>>the current drawn . For connection to a Viom/Netiom you can't use
mains
>>voltage directly so the lighter duty 12V/24V rated ones are
probably the
>>ones to go for. This level of signal can directly attach to a
>>VIOM/Netiom input - (the current is not important here at all). It
would
>>be possible to use mains switching PIR's by making them switch a
relay
>>and then use the contacts on the relay into the Netiom. The relays
>>isolate the mains voltage from the contacts ,and hence the Netiom,
>>making it useable and safe. However this means mains wiring outside
>>which always needs more care and it is harder to wire using the
relay.
>>
>>
>
>Now I am confused... If the contacts in the PIR are rated 230V to
>indicate that they can handle such a voltage, can they not just as
>well open or close a 12V load ?
>
>
Well that's sound logic  - where I really confused you was saying what
what goes in comes out....    In the 230V mains versions to ease the
wiring the 230V is normally fed in automatically, internal to the casing
- ie the contacts are not volts free and the input is connected to the
live feed so you get a switched 'live' output that you can just connect
to a mains floodlight or something.  Hence you couldn't connect 12V to it.

>Is this correct:
>- there is a power circuit for the PIR to make it operate
>
>
>- there is a power circuit for the NETIOM
>
>
yep for those two - although you can probably use the same one for both

>- there is a power circuit that can be opened and closed by the PIR
>and tested for open/closed by NETIOM ?  This is not "automatically
>provided" by NETIOM ?
>
>
Sort of -   I suppose for ease of understanding you can look at it this
way and ceratinly it can be implemented that way. The Netiom also has
the ability to detect a 'short' across its terminals which is not
effectively a power circuit just a set of open/closed contacts with no
voltage generated by the PIR contacts.

Kevin


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