Help on PIR connected to stamp2.
Archiver
Posts: 46,084
Hi all,
My project is a Surveillance system for my final project of my degree. I
bought a BS2 starter kit, so I have the carrier Board.
I'm V. new to the Basic Stamp world and I want to connect a PIR sensor
to my BS2.
This is probably a really simple query but:-
I welcome any advice on
where to buy a suitable PIR sensor and
on how you connect a PIR to the BS2.
Cheers,
KATH
My project is a Surveillance system for my final project of my degree. I
bought a BS2 starter kit, so I have the carrier Board.
I'm V. new to the Basic Stamp world and I want to connect a PIR sensor
to my BS2.
This is probably a really simple query but:-
I welcome any advice on
where to buy a suitable PIR sensor and
on how you connect a PIR to the BS2.
Cheers,
KATH
Comments
> on how you connect a PIR to the BS2.
Try acroname for the Eltec sensor, they have project notes on how to hook
it to a basic stamp using a comparator. It's easy to interface following
their instructions.
Good luck,
Jim Munro
<jimmn@x...>
> bought a BS2 starter kit, so I have the carrier Board.
>
> I'm V. new to the Basic Stamp world and I want to connect a PIR sensor
> to my BS2.
> This is probably a really simple query but:-
> I welcome any advice on
> where to buy a suitable PIR sensor and
> on how you connect a PIR to the BS2.
Check out http://www.mpja.com. They often have very reasonably priced
PIR kits or sensors.
DLC
--
============================================================================
* Dennis Clark Aristocrat at heart dlc@v... www.verinet.com/~dlc *
* Be well, do good work, and stay in touch -- Garrison Keillor *
============================================================================
direction of travel, etc. Then you will need a ADC, which the BS don't have.
Try http://www.geocities.com/SiliconValley/Orchard/6633/ Shaun has a good
tutorial on making a ADC for real cheap (the chip is free from Maxim). If
you just want an off/on PIR detection you can always hack a motion detector
from Wal-Mart. Try www.seattlerobtics.org and go to the encoder and search
for the article on hacking the PIR sensor.
-William
Original Message
From: Kath <Kath@i...>
To: <basicstamps@egroups.com>
Sent: Thursday, March 30, 2000 10:35 AM
Subject: [noparse][[/noparse]basicstamps] Help on PIR connected to stamp2.
> Hi all,
>
> My project is a Surveillance system for my final project of my degree. I
> bought a BS2 starter kit, so I have the carrier Board.
>
> I'm V. new to the Basic Stamp world and I want to connect a PIR sensor
> to my BS2.
> This is probably a really simple query but:-
> I welcome any advice on
> where to buy a suitable PIR sensor and
> on how you connect a PIR to the BS2.
>
>
> Cheers,
>
> KATH
>
>
>
>
> eGroups.com home: http://www.egroups.com/group/basicstamps
> http://www.egroups.com - Simplifying group communications
>
>
>
>
sensor and
had it working at 30+ feet good luck.
The usual PIR sensor produces a tiny voltage that has a peak frequency
response at around 0.1 hertz-->10 hertz, and drops off rapidly at DC and at
higher frequencies. So you need a high-gain AC preamp. The Phillips
app-notes recommend an op-amp circuit that self-biases for zero output at
DC:
+Vcc
--- Vcc
| | signal |\| LM358
| |
|+\
|PIR| | >
;- AC gain x1000, DC gain=0.
| | ;-- |-/ |
--- | |/ |
| | |
| ;--/\/\---'----/\/\----'
| | 1k 1M
| === 10uf
| |
Vss
For longer range you have to use lenses. There are several companies that
make infrared lenses commonly found on burglar alarms. The multifaceted
Fresnel lenses break up the hot body walking by into an AC signal on the
sensor. The lens is not necessary for detecting a hot body within that
shorter 3-foot range. A company called "Fresnel Technologies" makes many
patterns of lenses for special applications. I've used 4" diameter
circular lenses & PIR for counting bats and other animals for field
biology.
-- Tracy Allen
http://www.emesystems.com
mailto:emesys@c...
Kath wrote:
>
> Hi all,
>
> My project is a Surveillance system for my final project of my degree. I
> bought a BS2 starter kit, so I have the carrier Board.
>
> I'm V. new to the Basic Stamp world and I want to connect a PIR sensor
> to my BS2.
> This is probably a really simple query but:-
> I welcome any advice on
> where to buy a suitable PIR sensor and
> on how you connect a PIR to the BS2.
>
> Cheers,
>
> KATH
>
>
>
> eGroups.com home: http://www.egroups.com/group/basicstamps
> http://www.egroups.com - Simplifying group communications
- have ordered a sensor from acroname.
Cheers,
Kath.
security alarm, and desolder the actual PIR? It looks like a can with three
leads and a window at top. I can't decipher much from your art. Can you send
me a shemo? Thanks a bunch. BTW I'd like to do this with Rat Shack
components. Feasible?
-William
Original Message
From: LarryGaminde <lgaminde@t...>
To: <basicstamps@egroups.com>
Sent: Thursday, March 30, 2000 10:43 PM
Subject: [noparse][[/noparse]basicstamps] Re: Help on PIR connected to stamp2.
> This is something that Tracy Allen sent to me, It works! I also hacked an
alarm sensor and
> had it working at 30+ feet good luck.
>
> The usual PIR sensor produces a tiny voltage that has a peak frequency
> response at around 0.1 hertz-->10 hertz, and drops off rapidly at DC and
at
> higher frequencies. So you need a high-gain AC preamp. The Phillips
> app-notes recommend an op-amp circuit that self-biases for zero output at
> DC:
>
> +Vcc
> --- Vcc
> | | signal |\| LM358
> | |
|+\
> |PIR| | >
;- AC gain x1000, DC gain=0.
> | | ;-- |-/ |
> --- | |/ |
> | | |
> | ;--/\/\---'----/\/\----'
> | | 1k 1M
> | === 10uf
> | |
> Vss
>
> For longer range you have to use lenses. There are several companies that
> make infrared lenses commonly found on burglar alarms. The multifaceted
> Fresnel lenses break up the hot body walking by into an AC signal on the
> sensor. The lens is not necessary for detecting a hot body within that
> shorter 3-foot range. A company called "Fresnel Technologies" makes many
> patterns of lenses for special applications. I've used 4" diameter
> circular lenses & PIR for counting bats and other animals for field
> biology.
>
> -- Tracy Allen
> http://www.emesystems.com
> mailto:emesys@c...
>
>
>
>
> Kath wrote:
> >
> > Hi all,
> >
> > My project is a Surveillance system for my final project of my degree. I
> > bought a BS2 starter kit, so I have the carrier Board.
> >
> > I'm V. new to the Basic Stamp world and I want to connect a PIR sensor
> > to my BS2.
> > This is probably a really simple query but:-
> > I welcome any advice on
> > where to buy a suitable PIR sensor and
> > on how you connect a PIR to the BS2.
> >
> > Cheers,
> >
> > KATH
> >
> >
> >
> > eGroups.com home: http://www.egroups.com/group/basicstamps
> > http://www.egroups.com - Simplifying group communications
>
>
> -- Check out your group's private Chat room
> -- http://www.egroups.com/ChatPage?listName=basicstamps&m=1
>
>
>
out ( the sensor ran off 12 vdc) so now all I needed was a 5 vdc
supply. Next I removed the relay and installed a pot where the relay
coil was connected then I hooked up the stamp pin to one side of pot.
It is worked at long range because it came with a lens that fits the
sensor housing and looks good. The reason I removed the relay was
because of the power drain installing the pot allowed me to have the
sensor still turn on and off reliably but with only 20 mA drain vs
maybe 75mA ++. as far as viewing goes change from a variable width
font to a fixed width font and you will be able to view he picture.
William Ox wrote:
>
> Hey Larry and Tracy, I've been meaing to ask about this. Can I just hack a
> security alarm, and desolder the actual PIR? It looks like a can with three
> leads and a window at top. I can't decipher much from your art. Can you send
> me a shemo? Thanks a bunch. BTW I'd like to do this with Rat Shack
> components. Feasible?
> -William
>
>
Original Message
> From: LarryGaminde <lgaminde@t...>
> To: <basicstamps@egroups.com>
> Sent: Thursday, March 30, 2000 10:43 PM
> Subject: [noparse][[/noparse]basicstamps] Re: Help on PIR connected to stamp2.
>
> > This is something that Tracy Allen sent to me, It works! I also hacked an
> alarm sensor and
> > had it working at 30+ feet good luck.
> >
> > The usual PIR sensor produces a tiny voltage that has a peak frequency
> > response at around 0.1 hertz-->10 hertz, and drops off rapidly at DC and
> at
> > higher frequencies. So you need a high-gain AC preamp. The Phillips
> > app-notes recommend an op-amp circuit that self-biases for zero output at
> > DC:
> >
> > +Vcc
> > --- Vcc
> > | | signal |\| LM358
> > | |
|+\
> > |PIR| | >
;- AC gain x1000, DC gain=0.
> > | | ;-- |-/ |
> > --- | |/ |
> > | | |
> > | ;--/\/\---'----/\/\----'
> > | | 1k 1M
> > | === 10uf
> > | |
> > Vss
> >
> > For longer range you have to use lenses. There are several companies that
> > make infrared lenses commonly found on burglar alarms. The multifaceted
> > Fresnel lenses break up the hot body walking by into an AC signal on the
> > sensor. The lens is not necessary for detecting a hot body within that
> > shorter 3-foot range. A company called "Fresnel Technologies" makes many
> > patterns of lenses for special applications. I've used 4" diameter
> > circular lenses & PIR for counting bats and other animals for field
> > biology.
> >
> > -- Tracy Allen
> > http://www.emesystems.com
> > mailto:emesys@c...
> >
> >
> >
> >
> > Kath wrote:
> > >
> > > Hi all,
> > >
> > > My project is a Surveillance system for my final project of my degree. I
> > > bought a BS2 starter kit, so I have the carrier Board.
> > >
> > > I'm V. new to the Basic Stamp world and I want to connect a PIR sensor
> > > to my BS2.
> > > This is probably a really simple query but:-
> > > I welcome any advice on
> > > where to buy a suitable PIR sensor and
> > > on how you connect a PIR to the BS2.
> > >
> > > Cheers,
> > >
> > > KATH
> > >
> > >
> > >
> > > eGroups.com home: http://www.egroups.com/group/basicstamps
> > > http://www.egroups.com - Simplifying group communications
> >
> >
> > -- Check out your group's private Chat room
> > -- http://www.egroups.com/ChatPage?listName=basicstamps&m=1
> >
> >
> >
able to get it to work. But then again, I've only tried once [noparse]:)[/noparse]
Unfortunately the detector I'm using has a 4 second delay between updates.
Isn't there any schematic out there about how to build you own circuit? I
want one that gives a analog voltage (as opposed to digital off/on), like
the Acroname one, without the price. I know this is really ambitious, but
I'm interested....
-William
Original Message
From: LarryGaminde <lgaminde@t...>
To: <basicstamps@egroups.com>
Sent: Friday, April 07, 2000 2:11 PM
Subject: Re: [noparse][[/noparse]basicstamps] Re: Help on PIR connected to stamp2.
> What I did is hack a alarm sensor, I found the regulator and took it
> out ( the sensor ran off 12 vdc) so now all I needed was a 5 vdc
> supply. Next I removed the relay and installed a pot where the relay
> coil was connected then I hooked up the stamp pin to one side of pot.
> It is worked at long range because it came with a lens that fits the
> sensor housing and looks good. The reason I removed the relay was
> because of the power drain installing the pot allowed me to have the
> sensor still turn on and off reliably but with only 20 mA drain vs
> maybe 75mA ++. as far as viewing goes change from a variable width
> font to a fixed width font and you will be able to view he picture.
>
> William Ox wrote:
> >
> > Hey Larry and Tracy, I've been meaing to ask about this. Can I just hack
a
> > security alarm, and desolder the actual PIR? It looks like a can with
three
> > leads and a window at top. I can't decipher much from your art. Can you
send
> > me a shemo? Thanks a bunch. BTW I'd like to do this with Rat Shack
> > components. Feasible?
> > -William
> >
> >
Original Message
> > From: LarryGaminde <lgaminde@t...>
> > To: <basicstamps@egroups.com>
> > Sent: Thursday, March 30, 2000 10:43 PM
> > Subject: [noparse][[/noparse]basicstamps] Re: Help on PIR connected to stamp2.
> >
> > > This is something that Tracy Allen sent to me, It works! I also
hacked an
> > alarm sensor and
> > > had it working at 30+ feet good luck.
> > >
> > > The usual PIR sensor produces a tiny voltage that has a peak frequency
> > > response at around 0.1 hertz-->10 hertz, and drops off rapidly at DC
and
> > at
> > > higher frequencies. So you need a high-gain AC preamp. The Phillips
> > > app-notes recommend an op-amp circuit that self-biases for zero output
at
> > > DC:
> > >
> > > +Vcc
> > > --- Vcc
> > > | | signal |\| LM358
> > > | |
|+\
> > > |PIR| | >
;- AC gain x1000, DC gain=0.
> > > | | ;-- |-/ |
> > > --- | |/ |
> > > | | |
> > > | ;--/\/\---'----/\/\----'
> > > | | 1k 1M
> > > | === 10uf
> > > | |
> > > Vss
> > >
> > > For longer range you have to use lenses. There are several companies
that
> > > make infrared lenses commonly found on burglar alarms. The
multifaceted
> > > Fresnel lenses break up the hot body walking by into an AC signal on
the
> > > sensor. The lens is not necessary for detecting a hot body within that
> > > shorter 3-foot range. A company called "Fresnel Technologies" makes
many
> > > patterns of lenses for special applications. I've used 4" diameter
> > > circular lenses & PIR for counting bats and other animals for field
> > > biology.
> > >
> > > -- Tracy Allen
> > > http://www.emesystems.com
> > > mailto:emesys@c...
> > >
> > >
> > >
> > >
> > > Kath wrote:
> > > >
> > > > Hi all,
> > > >
> > > > My project is a Surveillance system for my final project of my
degree. I
> > > > bought a BS2 starter kit, so I have the carrier Board.
> > > >
> > > > I'm V. new to the Basic Stamp world and I want to connect a PIR
sensor
> > > > to my BS2.
> > > > This is probably a really simple query but:-
> > > > I welcome any advice on
> > > > where to buy a suitable PIR sensor and
> > > > on how you connect a PIR to the BS2.
> > > >
> > > > Cheers,
> > > >
> > > > KATH
> > > >
> > >
>
> > > >
> > > > eGroups.com home: http://www.egroups.com/group/basicstamps
> > > > http://www.egroups.com - Simplifying group communications
> > >
> >
>
> > > -- Check out your group's private Chat room
> > > -- http://www.egroups.com/ChatPage?listName=basicstamps&m=1
> > >
> > >
> > >
>
>
>
turned on it stayed on for maybe a second or two, as far as variable
voltage I can't help (what advantage would this have ?) I could see if
you were looking for temp using IR but what advantage for detecting a
hot body walking by. There is a schematic, I sent it with the first
mail try to highlight it copy it and then use notepad and view it
there but again its only on / off Sorry.
William Cox wrote:
>
> Hmmm .... yes I did this according to the tutorial on SRS. I haven't been
> able to get it to work. But then again, I've only tried once [noparse]:)[/noparse]
> Unfortunately the detector I'm using has a 4 second delay between updates.
> Isn't there any schematic out there about how to build you own circuit? I
> want one that gives a analog voltage (as opposed to digital off/on), like
> the Acroname one, without the price. I know this is really ambitious, but
> I'm interested....
> -William
>
>
Original Message
> From: LarryGaminde <lgaminde@t...>
> To: <basicstamps@egroups.com>
> Sent: Friday, April 07, 2000 2:11 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Re: Help on PIR connected to stamp2.
>
> > What I did is hack a alarm sensor, I found the regulator and took it
> > out ( the sensor ran off 12 vdc) so now all I needed was a 5 vdc
> > supply. Next I removed the relay and installed a pot where the relay
> > coil was connected then I hooked up the stamp pin to one side of pot.
> > It is worked at long range because it came with a lens that fits the
> > sensor housing and looks good. The reason I removed the relay was
> > because of the power drain installing the pot allowed me to have the
> > sensor still turn on and off reliably but with only 20 mA drain vs
> > maybe 75mA ++. as far as viewing goes change from a variable width
> > font to a fixed width font and you will be able to view he picture.
> >
> > William Ox wrote:
> > >
> > > Hey Larry and Tracy, I've been meaing to ask about this. Can I just hack
> a
> > > security alarm, and desolder the actual PIR? It looks like a can with
> three
> > > leads and a window at top. I can't decipher much from your art. Can you
> send
> > > me a shemo? Thanks a bunch. BTW I'd like to do this with Rat Shack
> > > components. Feasible?
> > > -William
> > >
> > >
Original Message
> > > From: LarryGaminde <lgaminde@t...>
> > > To: <basicstamps@egroups.com>
> > > Sent: Thursday, March 30, 2000 10:43 PM
> > > Subject: [noparse][[/noparse]basicstamps] Re: Help on PIR connected to stamp2.
> > >
> > > > This is something that Tracy Allen sent to me, It works! I also
> hacked an
> > > alarm sensor and
> > > > had it working at 30+ feet good luck.
> > > >
> > > > The usual PIR sensor produces a tiny voltage that has a peak frequency
> > > > response at around 0.1 hertz-->10 hertz, and drops off rapidly at DC
> and
> > > at
> > > > higher frequencies. So you need a high-gain AC preamp. The Phillips
> > > > app-notes recommend an op-amp circuit that self-biases for zero output
> at
> > > > DC:
> > > >
> > > > +Vcc
> > > > --- Vcc
> > > > | | signal |\| LM358
> > > > | |
|+\
> > > > |PIR| | >
;- AC gain x1000, DC gain=0.
> > > > | | ;-- |-/ |
> > > > --- | |/ |
> > > > | | |
> > > > | ;--/\/\---'----/\/\----'
> > > > | | 1k 1M
> > > > | === 10uf
> > > > | |
> > > > Vss
> > > >
> > > > For longer range you have to use lenses. There are several companies
> that
> > > > make infrared lenses commonly found on burglar alarms. The
> multifaceted
> > > > Fresnel lenses break up the hot body walking by into an AC signal on
> the
> > > > sensor. The lens is not necessary for detecting a hot body within that
> > > > shorter 3-foot range. A company called "Fresnel Technologies" makes
> many
> > > > patterns of lenses for special applications. I've used 4" diameter
> > > > circular lenses & PIR for counting bats and other animals for field
> > > > biology.
> > > >
> > > > -- Tracy Allen
> > > > http://www.emesystems.com
> > > > mailto:emesys@c...
> > > >
> > > >
> > > >
> > > >
> > > > Kath wrote:
> > > > >
> > > > > Hi all,
> > > > >
> > > > > My project is a Surveillance system for my final project of my
> degree. I
> > > > > bought a BS2 starter kit, so I have the carrier Board.
> > > > >
> > > > > I'm V. new to the Basic Stamp world and I want to connect a PIR
> sensor
> > > > > to my BS2.
> > > > > This is probably a really simple query but:-
> > > > > I welcome any advice on
> > > > > where to buy a suitable PIR sensor and
> > > > > on how you connect a PIR to the BS2.
> > > > >
> > > > > Cheers,
> > > > >
> > > > > KATH
> > > > >
> > > >
> >
> > > > >
> > > > > eGroups.com home: http://www.egroups.com/group/basicstamps
> > > > > http://www.egroups.com - Simplifying group communications
> > > >
> > >
> >
> > > > -- Check out your group's private Chat room
> > > > -- http://www.egroups.com/ChatPage?listName=basicstamps&m=1
> > > >
> > > >
> > > >
> >
> >
> >
> I just hack a security alarm, and desolder the actual PIR?
> It looks like a can with three leads and a window at top.
> I can't decipher much from your art. Can you send me a shemo?
> Thanks a bunch. BTW I'd like to do this with Rat Shack
> components. Feasible?
>.....
> Unfortunately the detector I'm using has a 4 second delay between
> updates. Isn't there any schematic out there about how to build
> you own circuit? I want one that gives a analog voltage (as opposed
> to digital off/on), like the Acroname one, without the price. I know
> this is really ambitious, but
> -William
Hi William,
Yes, the PIR from the alarm should work just fine. I guess you need
faster response and an analog output, so you can't simply hack the whole
alarm. I was faced with a similar need to make my own circuit, because it
was for an animal counter for flying bats that had to respond very fast.
I'll try again with the ascii art to show more of the connections and pin
numbers:
;
o
Vcc 5 volts
| |
--- Vcc
| | signal 3|\|8 LM358
| |
|+\
|PIR| | >1----o- AC gain x1000, DC gain=0.
| | ;--|-/ |
--- | 2|/|4 |
| | | |
| ;--/\/\---o----+-/\/\-'
| | 1k | 1M
| === 10uf |
| | |
'----o
o
Vss
The resting voltage level at both pin 3 and pin 1 of the op amp will be a
few tenths of a volt, until something comes by that excites the PIR sensor.
The voltage at the input pin 3 will shift by a few millivolts. The output
at pin 1 will shift by a volt or more. The circuit tracks slow changes in
the PIR output, with a time constant determined by the 1M resistor and the
10uf capacitor. But the gain for fast changes is x1000, because of the
ratio of 1M/1k resistors. This is a standard circuit for PIR sensors. It
takes the circuit 10 or 20 seconds to "warm up" as the capacitor charges up
to the resing level. What do you want to do with the analog signal once
you have it? It could go into a comparator circuit to square up the level
changes. More signal processing may be desireable to reject "false
alarms".
I hope that helps,
-- Tracy Allen
Electronically Monitored Ecosystems
http://www.emesystems.com
bot the ability to detect people, and the direction their moving. I've also
thought about the Trinity competition. I tried hacking just the motion
sensor, but the 4 second time lag was just too much, no to mention the
digital signal. This *seems* to be a simple circuit. How come so many people
opt out for the $40 all in one from Acroname? I know it's a whole lot
easier, but the price difference (IMHO) out weights it. I'll see what I can
do with it. Thanks again. BTW I've understood that a PIR (such as the
Acroname one) has a sine wave output (sort of), if a person was to walk
across it. Is this true for this circuit?
-William
> Hi William,
> Yes, the PIR from the alarm should work just fine. I guess you need
> faster response and an analog output, so you can't simply hack the whole
> alarm. I was faced with a similar need to make my own circuit, because it
> was for an animal counter for flying bats that had to respond very fast.
> I'll try again with the ascii art to show more of the connections and pin
> numbers:
>
> ;
o
Vcc 5 volts
> | |
> --- Vcc
> | | signal 3|\|8 LM358
> | |
|+\
> |PIR| | >1----o- AC gain x1000, DC gain=0.
> | | ;--|-/ |
> --- | 2|/|4 |
> | | | |
> | ;--/\/\---o----+-/\/\-'
> | | 1k | 1M
> | === 10uf |
> | | |
> '----o
o
Vss
>
> The resting voltage level at both pin 3 and pin 1 of the op amp will be a
> few tenths of a volt, until something comes by that excites the PIR
sensor.
> The voltage at the input pin 3 will shift by a few millivolts. The
output
> at pin 1 will shift by a volt or more. The circuit tracks slow changes in
> the PIR output, with a time constant determined by the 1M resistor and the
> 10uf capacitor. But the gain for fast changes is x1000, because of the
> ratio of 1M/1k resistors. This is a standard circuit for PIR sensors. It
> takes the circuit 10 or 20 seconds to "warm up" as the capacitor charges
up
> to the resing level. What do you want to do with the analog signal once
> you have it? It could go into a comparator circuit to square up the level
> changes. More signal processing may be desireable to reject "false
> alarms".
>
> I hope that helps,
>
> -- Tracy Allen
> Electronically Monitored Ecosystems
> http://www.emesystems.com
>
>
>
>
> wave output (sort of), if a person was to walk
> across it. Is this true for this circuit?
It is true, under "ideal" conditions the signal looks like one cycle of a
sine wave. You have to realize that the PIR sensor (most PIR sensors that
is) contain a pair of heat sensitive elements hooked up in series
opposition, kind of like:
+--+
like two tiny batteries hooked up so that their voltages cancel. For
changes in ambient temperature and slow changes in infrared energy, the two
voltages change by equal amounts, so they cancel. But the two elements are
positioned side by side behind the window in the PIR package. The image
of a warm object is focused by the lens that is normally put as a distance
in front of the PIR sensor. As the image of the warm object moves across
the sensor in one direction, it heats up first the (+-) element and then
the (-+) element, so that you get first an excess of voltage in one
direction and then in the other direction. It is like a single cycle of a
sine wave. If the image of the object moves in the other direction, then
you get the opposite phase. So under ideal circumstances you can tell
which direction the object is moving by looking a the phase of the pulses.
A positive cycle followed by a negative cycle is motion in one direction,
while a negative cycle followed by a positive cycle is motion in the
opposite direction. But I said "ideal"--caveat, the unrestained movement
of bodies is seldom ideal. One half of the pulse may come out much larger
than the other, or one half of the pulse may be missing altogther. BTW
some of the cheapest PIR sensors only have one element:
+-
and have higher ambient drift and a different response characteristic.
A lot depends on the lens that is put in front of the PIR sensor, because
it is the lens that forms the sharp image. Some lenses have many facets
that point in different directions into different zones. So a person
walking across forms a whole succession of images that march across the
face of the PIR sensor and make a sequence of signals. Other simple
cylindrical lenses form one strong image. Lots of variation. See Fresnel
Technologies site for an idea of the variety of lenses available:
http://www.fresneltech.com/
> This *seems* to be a simple circuit. How come so many people
> opt out for the $40 all in one from Acroname? I know it's a whole lot
> easier, but the price difference (IMHO) out weights it. I'll see what I
can
> do with it.
I don't know about the Acroname circuit. Well, the circuit I gave is just
a start. It is the core to allow you to get a big signal. But as you get
into it more, you may find you need some more filtering or faster power on,
or bells and whistles. Not to mention the lens and the enclosure and the
PC board, and the engineering. I'd say $40 is not at all an unreasonable
price! When I have made things like this for my clients, I have to charge
them a lot more than that! This kind of circuit is built up of many
blocks, and each block serves some simple purpose for what you or the
commercial design was trying to accomplish. Maybe you just need the core of
it to start with to experiment and learn.
-- Tracy Allen
Electronically Monitored Ecosystems
http://www.emesystems.com