Removing PIR

Rooter

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Has anyone ever tried to remove the PIR sensor from an MS20 and then mounting it separate from its board?  Is there a reason why it can't or shouldn't be done?
 

Brian

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Cam Trakker does it in theirs so I assume it works.  Just don't use really really long wires.  I plan on trying it myself but not with the MS20.

Be very careful unsoldering.  Don't over heat the PIR when removing it.
 

coyotehunters

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IF THIS IS THE CASE A GUY COULD REMOVE THE PIR AND MOUNT IT ON THE DOOR WITH THE FRESNAL LENSE AND ONLY HAVE TO RUN THE THREE WIRES TO THE BOARD THAT IS MOUNTED IN THE BOX.THAT SOUNDS LIKE ALOT SIMPLIER DEAL THAN MOUNTING THE BOARD ON THE DOORAND RUNNING ALL THE WIRES TO THE SWITCHES LIKE I HAVE BEEN DOING.
 

Rooter

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Brian, you said not to use long wires.  Will this affect performance and what in your opinion is "long?"  I am thinking that I will mount the sensor separate from the board.  It will allow me to make better use of the space inside of the case.  In the case of the MS20 I would like to lose a little range anyway.  Thanks for your expertise.

Rooter

(Edited by Rooter at 1:57 pm on Mar. 20, 2002)
 

ArkansasElkHunter

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Rooter,

If you will mount the sensor about 0.8" fromthe fresnal lens it will tone the ms20 sensor down to about 35 feet or so.  Check out the thread on "MS20 sensitivity"
 

Brian

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I am not sure on the wire length since i haven't done it.  The cam trakker wires were about 4 to 6 " at most.  THe only thing I would be worried about it the resistance due to the wire length but since it is at the sensor and not in the feedback loop of the circuit I don't think that it will matter a whole bunch.

I plan on playing with this one day but I haven't got around to it.  Worst case you have to put it back or replace it if damaged so why not try it.  Try to use as short of wires as possible and go from there that is what I was going to do when I got to it.
 

ArkansasElkHunter

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I removed a sensor from the ms20 board tonight and used 4 inch wires to connect it to the board.  I thought it was triggering randomly at first but it seems to have settled out.  I'm going to leave it on tonight and let the event counter on brians chip tell me if it triggers without any thing around.  I have'n mounted it in a dhousing. its just dangeling out of one of my cameras. If it works it will sure cut down on the surface area of the enclosures.   I was'nt sure I did not damage it when i removed it.  If any knows where to get a cheap replacement they are bound to have longer leads and then removal would not make them questionable.  I don't know one KDS from another.
 

ArkansasElkHunter

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Well, I'm not sure if I messed up the sensor or not but the event counter had 113 events overnight.  The room was shut and there was nothing in there.  I'll put the same sensor back in the board and try in this weekend.  
 

Rooter

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Perhaps you have ghosts in your house?:angel-halo:

(Edited by Rooter at 10:46 am on Mar. 22, 2002)
 

ArkansasElkHunter

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Brian says that is typical of the oscilation problems he was having.  I may have a few ghosts in the closet, but there I hope there arn't any in the house.  There is something in my 4 yr olds closet that she worries about.  It likes the light left on.
 

Brian

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I was afraid that would happen.

I am guessing that it is the feedback instability caused by the additional wire length.  I solved this problem with my boards when the trace lengths were doing the same thing and I am not famaliar enough with the MS20 to know what to do about it.  I am going to try and remove my PIR from my design and see how it reacts.  If it is stable then my changes would work for the MS20 too if someone knew the design well enought to know where to implement them.  I will have to dig up Tinhorn's schematic and see if I can solve this.
 

coyotebandit

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Would using a shielded cable help out? What does the output of the PIR look like on a scope? What about an EMF filter? Boy I really wish I would have stayed in electronics, it's true what they say, "If you don't use it, you lose it!". I think I lost it, or at least most of it!
 

Rooter

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Coyotebandit, it is better to have had it and lost it then never had it at all.  My electrical background is minimal.  I know not to stick my fingers in an electrical socket.  I am more of a mechanical tinkerer.  I do know that if anyone can solve it some of you guys can.

:frankenstein:
Rooter
 

Brian

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Coyotebandit,

The shielded cable will not work.  It is related to the internal resistance of the wire.  I used a trace over a dielectric constant board with the calculations used to create a minimum resistance load on the circuit and it still seemed to affect it.

The output specs for the PIR can be found on this site.  Scroll down until you see the output signal.  I have checked it on a scope and it looks just like this.  A volt meter can catch it too but you will have to know how to intrepret it or it looks odd.

http://www.glolab.com/pirparts/infrared.html
 

coyotebandit

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Brian,
So I suppose the only way to make this work would be to make a small board with the whole PIR circuit on it. Then having the power, and transistor driven output run through a set of wires that connect to the timer circuit. It sounds like a good surface mount project for you. Do you think that would work? Are using a modified version of the Golab circuit for your all in one PIR & timer boards?
 

Archilochus

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Hi guys,
I don't know if this idea could be made to work with the MS 20 or RS 49-425.
But if you're building your own boards, just put all the sensitive analog portions of the circuit on the PCboard with the PIR element.  You're only looking at 1 IC and some passives to go with it.  I got it down to about 1.25 sq. in. on my "micro" cam.
You'd only need +V, gnd, and one digital output.

Archilochus
 

shrtcirkt

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Here are a couple of pics of the amazon pir front and back. I had some trouble with this unit oscillating at first using it with JoeD's timer, but a $.25 voltage regulator cured that problem. I just finished testing two of these along with amazon's low cost version (it does nothave the chip) and it worked well. Today it is mid 30's and winds are gusting to 25MPH. The low cost version had 132 false triggers, the one in the pic had 0 false triggers, and sensed my movement out to about 60'. Just something I thought you might be interested in.
Sorry the pics are not better, the EZ 1.3 does not take a real good close up.



 

shrtcirkt

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I should add one more thing... the output of this PIR is a + voltage. if you are going to use it with JoeD's timer, or Brians (i think) you will need to use a voltage inverter at the output. brian sent me a schematic for a nice one using a single transistor and 2 resistors.
So far it has worked great.
 

coyotebandit

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shrtcirkt,

What is the difference between the low cost version, and the higher cost version? What regulated voltage are you running them off of? I have two of these, but I don't know if they are the cheaper ones or not? I think mine only claims its good out to 3 m, that wouldn't work to well in a cam, but it looks just like the one you posted.

I found that the EZ digital works much better on close ups if you use the macro mode switch.

Also, doesn't the RS pir trigger high? I'm thinking you wouldn't need to use anything special to use this with a JoeD timer.

CB





(Edited by coyotebandit at 9:21 am on Mar. 25, 2002)
 

shrtcirkt

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CB,
The higher cost version uses the KC778B chipset, which gives the unit more flexibility, I had a lot of problems with the low cost unit "false triggering". I added a 5 volt regulator to eliminate the spike that happens when JoeD's timer finishes it's count and goes to sleep. This spike was causing the PIR to trip and starting an endless loop.
I am not sure if the RS triggers high, but JoeD's timer triggers low, so I put the inverter on the PIR output and it works well.
These units are rated at 3m, but I have yet to have one not work at under 30'
 

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