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RE: Homevision and PIR's



Malcolm,
 
Firstly - well done - I congratulate you as a man of obvious good taste and discretion in your choice of HA system.
 
To turn to latency - I think that the biggest problem with the X10 PIRs is that they're not "continuous scan". Instead, they scan the zone every xxx seconds. Compared to that, the .5 second delay of firing a pair of X-10 messages round (one from PIR to HV, one from HV to whichever devices you want to control as a result) is small.
 
The most consistently succesfull way of approaching that is to have a PIR plug beam break, in conjunction with an HV timer. The beam break plugs into a HV input port.
 
Basically, what happens is as follows:
 
- If either the beam break or the timer triggers, turn on the light
- If the beam break triggers, set the timer to 45 seconds, and count down.
- If the PIR triggers, set the timer to 10 minutes, and count down.
- When the timer gets to zero, turn the light off.
 
That means that when someone walks INTO the room, the light comes on quickly. The trouble is, a beam break can't tell whether it was someone going in or coming out... hence it only turns (leaves) the light on for 45 seconds.
 
... if someone was coming IN, then 45 seconds is plenty of time for the PIR to catch them.. and when THAT happens, the timer gets 10 minutes to play with... so the PIR only needs to "re-catch" them every 10 minutes.
 
... if a second person comes into the room, then the timer gets pulled down to 45 seconds, but that's STILL plenty of time for the PIR to cut in and wham it back to 10 minutes.
 
... if someone leaves the room, the time gets pulled down to 45 seconds, but that's STILL plenty of time for another person still in the room to be caught by the PIR.
 
... if someone leaves the room, and there's no-one left to trigger the PIR, the lights go off 45 seconds later.
 
Now, in a "destination room", then this is simple, 'cos there's only only doorway, and hence only 1 beam break.
 
In a "circulation room", it's harder, 'cos you need a beam break per entry.
 
See www.mollyology.com for more details on beam breaks.
 
M.
-----Original Message-----
From: Malcolm Passmoor [mailto:malcolm.passmoor@xxxxxxx]
Sent: Fri 04/10/2002 12:47
To: ukha_d@xxxxxxx
Cc:
Subject: [ukha_d] Homevision and PIR's

Hello folks,
 
 
Just in case you remember my name from a previous posting, I was the chap having some trouble in deciding whether to go for something like homeseer/cm12u or homevision - well I went for homevision and so far I haven't really done much with it - x10 stuff can be quite expensive to accumulate!
 
Any way, my first project is to do the "movement in the hall - lights on" thing and I heard some comment that the wireless X10 PIR/transceiver set up presents a bit of a lag in terms of response times - is this true? To cut a long story short and since I have HV with all of it IO capabilities I bought a relatively inexpensive response systems wired PIR - trouble is there are no installation guide and I'm a bit of an electronics novice - please please help.
 
The PIR is a 12v unit so I found a 12v PSU and connected it the appropriate terminals - its seems to flash when there's movement so I guess so far so good. I was assuming that I should now connect the N/C terminals to port B on the HV to pin and ground - Am I right - HV''s a bit pricey and I don't want to try it and fry it. Any help appreciated.
 
Malcolm.

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