Re: Unusual Challenge

[Bob La Londe <none@none.com99>]

On 10/20/2021 5:31 PM, ABLE1 wrote:
 > Hey Guys,
 >
 > Would like some thoughts on the following challenge.
 >
 > Customer has a showroom/office in one building and the shop in another
 > that is 70 feet away.  They wanted to have a way to get notified in the
 > shop that a potential customer came into the showroom.
 >
 > What I installed was a door contact switch on the entry door and wired
 > a Linear DXT-31 transmitter and a Linear DXT-701 Receiver in the shop.
 >
 >  From there I used the contacts on the receiver to trigger and Altronix
 > timer and the contacts there to trigger a horn/buzzer for about 1 sec.
 > when the door was opened.
 >
 > It has worked quite well for some time but, recently I was told that
 > it did not respond to ALL entering the showroom.
 >
 > I was there a couple of weeks ago and it was working but the the CR2032
 > batteries were about 60% level and I changed to new.  Tested the
 > batteries were at 100%. OK.
 >
 > I was then informed yesterday that it was still missing some entries.
 >
 > I stopped in today and first I tested the door 3 times and it did not
 > work.
 >
 > I tested the batteries.  They were at 100%
 >
 > I removed the transmitter and went to the shop and it worked 5 times
 > in a row.  Or let's say 100%  I put the transmitter back in the attic
 > above the showroom where it was but staff was in a meeting so I could
 > not test.
 >
 > Was told later that they tried it and it did not work a total of 3 times
 >
 > Now the receiver has a wire about 7" long as a antenna.  I have
 > it hanging over the edge of a window so that the walls would not block
 > the RF signal. The Transmitter is in the attic space on a vertical
 > 2x4.  The only thing that might block the signal would be the plywood
 > and asphalt shingles on the roof, 70' of distance, bug screen and glass
 > window.
 >
 > Needless to say this is a intermittent problem that is NOW not working!!
 >
 > So, any thoughts on this before I type something that really made a
 > difference this afternoon.
 >
 > Thanks for any thoughts!!
 >
 > Les
I do not recall which linear receivers I used, but on my shop overhead
doors I used some with the little F connector screw on antenna.  I then
used a piece of coax to take that antenna outside.  I get 100%
reliability (as long as the batteries in my remotes are good) and great
range.  My driveway is over 100 yards long to the front of the shop, and
with fresh batteries I get another 100-150 yards range up the road.
Maybe a little further if I hold the remote out the window of the truck.

Because I am actively involved in every activation I notice the
batteries start to go by the range the remote works at.  When the
batteries are low I have to be on my driveway, and sometimes hold the
remote button down for an extra half second before the receiver
recognizes the code.

If you are using a regular unsupervised door transmitter I think it just
sends the code once and that's it.  If the receiver doesn't recognize
the code it doesn't activate.  Placing the receiver antenna outside in a
manner similar to what I did may help. Another option might be to setup
some redundancy.  Set up contacts on the door with bias so that it
activates the transmitter both when the door opens and when the door
closes.  It may result in an annoying double notification buzz, and
battery life will likely be halved.  It might however be more reliable
for the intended purpose.

Still staying with your current application I suggest one day when you
take a break for lunch you park across the street and watch the door
while you mac out.  Maybe a couple different days if you are in the
area.  You may notice if the door doesn't always close properly or if
its held partly open when the wind blows from a particular direction.
Something as simple as repositioning the magnet so its just barely
within its clear change at maximum closing travel of the door and swings
through its full clear range before going into its triggered state.  If
a simple answer like a Z-bracket or spacers won't work you can also
consider moving the magnet and contact closer to the midpoint of the
door.  This has the same affect of allowing the door to open slightly
before triggering which can help overcome door conditions that may not
allow the circuit to reset otherwise.

Of course the door contact, transmitter, or receiver could also be
faulty.  Any lighting storms around the time the contact started acting
up?  We are all familiar with contacts being welded shut, but sometimes
they break free and act unreliably.

If triggering is an unresolvable issue with a door contact then photo
beams and IR curtains generally trigger more reliably than a door that
is standing open, but they have other issues.  The door could block the
beam.  The sun shining in a glass door or window can affect them.
Children running around like maniacs can cause runaway activations.
Mylar ballons tied to a fan can drive you crazy.

Getting further out there.  I once used a basic photo beam door chime
outdoors for a vehicle drive thru.  The customer thought it was great,
and it prevented me from having to cut the asphalt to put in a loop.  In
order to reduce false activations and low sensitivity I made a deep
steel hood out of steel tube and put it inside of it.  Something like
that might also work in a regular personnel door setting.  Most business
doors swing both ways or open out (per code) except possible at WalMart
where they lock customer area doors while customers are in the store in
the evenings.

Good luck.  I hope my rambling gave you something useful.

--
This email has been checked for viruses by AVG.
https://www.avg.com