X-Message-Number: 8267
From:  (Randy)
Subject: Member-down emergency alert system
Date: Sun, 01 Jun 1997 03:24:52 GMT

 I have been thinking of developing a member down alert system,
designed to alert by phone a cryo org in the event that a member has
not moved in a certain amount of time. This would hopefully avoid long
times of room temperature ischemia, thus allowing for better

 I may have finally found what may be an appropriate infrared
detector, an AMP (brand name) passive Infrared module (PIRM);
operating voltage 5 v dc, 2.0 mA, spectral response of 4 to 20
micrometers  -- what's the freq, and does it matter? Digital output;
normally low (+0.7 v max); Active high ( +3.8v min); Analog; Offset @
2.5 V. Anyone have any ideas on the meaning/relevance of the preceding
info, which comes from the spec sheet?

I have hooked up this detector  to a 5 V dc regulated powers supply
(no voltage divider; it's right across it). The steady-state (no
movement) output is ~2.18 V dc. Immediately after movement is sensed,
voltage quickly drops to zero and then reverses polarity and maxes out
at about -2.2 v dc and quickly reverts once again to 2.18 v if no
further movement is sensed. This transient occurs in about a 2 second
time frame( or less).

The range of this detector is about (insofar as I have determined)
about 10-12 feet. The detector detects motion through about 75 degrees
on the horizontal axis. However, the vertical axis is not nearly so
good, with a detection range of perhaps 30 degrees at 5 feet.

What I need help on is design of the circuit fed by the detector. I
was thinking perhaps a diode (zener?) which is biased into conduction
by the transient spike of opposite polarity voltage generated by
detected motion. The diode, during a brief conduction period, could
short to ground a resistive-capacitive circuit hooked up to the power
supply. The time constant of this RC circuit would be such that if it
is allowed to charge for, say, one hour (without being discharged by
zener), would then build up to a voltage level sufficient to bias into
conduction a solid state relay.

 On the other side of the solid state relay output would be the phone
and time delay circuits. I have a phone with 3 memory circuits. I have
accessed the memory button wiring and can short around these buttons
and the on-off switch. The plan would be that, once the RC circuit has
fully charged (no motion after one hour), the relay would close,
closing the on-off switch (taking the phone off the hook,
effectively), a time delay would then kick in, perhaps a couple of
seconds to allow for a dial tone, then another relay would close,
shorting out memory button one, which would dial a pager number for
one of the cryo org standby team.=20

The other time delay circuit would run a couple of seconds longer, and
then close another solid state relay contact, which would short memory
button 2, dialing the phone number for the cryo member's own phone,
which is then stored in the memory of the pager belonging to that
standby team member.=20

Of course, everything on the phone side of the relay is another
problem entirely, and can wait until the detection circuit is

I realize that this is a very modest attempt at a cryo alert system,
but we must start somewhere. This could begin with a one-detector
system set up by the bed of a cryo member with heart problems. It
would not be perfect, and could be reset manually by the member after
a false alarm, thereby simplifying the circuitry. An alarm circuit
would need to be included--more amps!

So if anyone has any ideas on the circuitry on the detector side of
the solid state relay, I would appreciate it.  Speaking of which,
those solid state relays aren't cheap, so I'll probably try to build
some from _Electronics_Now_ magazine  schematics. (The detector itself
is only $8).

Also, any ideas about testing this thing? I have a Fluke digital
multimeter with max, min, range, and delta functions. I have placed
the detector about  2 feet from my bed, and it does detect motion when
roll slightly, e.g.,  from laying on my right side, to my back.

This power supply I have has a single output, variable from 3 to 12
vdc, capable of 2 amps. Of course if different voltage levels are
needed, and of course, they will be, we need to devise voltage
dividers. I have spare fuses, of course. :-)

This alert system would be available to all cryo orgs. As of now, no
one has one, AFAIK, and it not only could save lives--if cryonics
works, etc--but also could improve quality of suspensions, helping to
bring in new members( if suspension reports are available). A
workable, cheap alert system would also say something about the
seriousness of cryonics.
Randy  =20
Cryonics: Gateway to the Future?
http://members.wbs.net/homepages/c/r/y/cryofan1.html            =20

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