MS-20 problems

treestandman

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I've got a problem with the ms-20 sensors; they occaisionally toglle on and off for a period of time. Sometimes this happens on powerup; sometimes after they have been in the field and working for a while--the sensor will be triggered and then start to toggle on and off. It doesn't seem to be a bbattery problem, I'm think it may be temperature related. Has anybody else had this experience? Has anyone developed a schematic for this unit?
 



dharter

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This has been discussed before.  You can use the search features of this forum to find info.
The ms20 has problems when the temperatures get up around 100 degrees.  I had a whole roll of pictures with nothing but scenery last week.  It might have been an animal on the ground out of sight of the camera, a bird, or air currents.  Or maybe the tree I am using is not thick enough and wind causes it to sway.  teh high temperature was only in the low 90s.
Here is one url to start with:
http://www.jesseshuntingpage.com/cgi-bin/i...1&topic=245
The ms20 uses an LM324 type op amp.  It would be interesting to put the ms20 in an oven, raise the temperature to 100 degrees, and view some of its waveforms on an oscilloscope.  Is the problem really the PIR  or a design flaw in the ms20?  The 1st stage of the ms20 appears to be a differentiator so it should respond to changes in the charge on the PIR and not matter what temperature it is.  The National Semiconductor databook for the LM324 has a sample comparator circuit in it.  that one has a 1 megaohm resistor connected from the output to the + input of the op-amp/comparator.  That is supposed to make the input signals have hysteresis.  You might try that to see what happens.  Or maybe one of the amplifier stages of the ms20 is oscillating.
 

Welby

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This seems to be very similar to a problem I had with my first camera.

I discovered one day as I was checking my camera that the sensor seemed to be "stuck".  So, I turned the unit off and then on again.  It came on fine, went through the thirty second warm up, and after a few seconds, it begin to trigger and re-trigger itself, slowly at first and then faster until finally it just locked up again.

Also thinking that it may be heat related (or moisture related) I allowed it to dry and/or cool off for a long period of time.  After this time (which was more than a day), I turned it on again.  For nearly two hours, it worked fine, but then it begin to act up again.  And it was in my air conditioned office at that time.

I still have the board from that camera and one day I intend to see if I can get it working again, but I really don't know enough about electronics to be much for troubleshooting.  I would sure love to know why this happened.
 

wfontjr

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throw that sensor away, i had a ms20 toggle off and on during february, never could get it to stop, replaced it with a new ms20, have had no problems with the next 10 of them except for high temperatures during the summer
 

Possum

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Okay, I feel like this is a good place to add to the discussion. I used the MS20 on my house for a while (or at least one that was close to it).  Every so often it would get to where it would keep the lights on all night.  I would try everything, even taking them apart to see if a bug was in them.  Sometimes I HAD to replace them. Then I went to the more expensive light sensors and did not have much of a problem after that.  Hey, for $9 switch the thing out or take it back to Wal Mart and get them to replace it.  For some reason they can get too sensitive to work correctly.  I wish we could figure out what the problem is and how to fix it.  Good luck everyone.  I do use this sensor and had a blank pic in the last 9 pics.  But, based on the time of the pic I would say the hog that is eating my corn tripped the pic before getting into the frame of the camera.
 

treestandman

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Many thanks for the responses and info--for some reason I did'nt find the schematics with my search before the original posting. I have several of these things exhibiting this problem, and now it seems to be happening in the middle of the night, using up all the film on flash pictures of the scenery. I'm goning to try to connect several points in the sensor toa datalogger and run it as soon as I find the time..if I get any useful info, I'll post it. Thanks again!
 

Tinhorn

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Treestandman

Here is the MS20 Schematic I reverse engineered several months ago.  

I've only had the MS20 toggle as you describe for 2 reasons, both rather common, either low battery's or dampness, but I know several has had some go bad for some reason (just like a Light Bulb, you never know when electronic things might burn out)

Hope this helps, Tinhorn

 


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