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nuckolls.bob(at)aeroelect
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 Posted: Tue Jun 13, 2017 2:07 pm Post subject: MP100701 Open Collector To Ground Position Sensor |
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Attached is a PDF data sheet of a sensor I think will work for my application. Could someone PLEASE look it over and tell me IF this sensor will work with my application?
I'm sure it will . . .
I like this particular sensor because it is the right dimensions (length and width) for my application (I have VERY LIMITED space) and this sensor is an open collector to ground that I need for the Dynon Skyview EMS…plus it is only 15 bucks!!!
. . . ain't 'lectronics wunderful?
The questions I have are:
-The data sheet states “Open Collector (NPN) output can be used with bipolar or cmos logic circuits with suitable pull up resistor”. I do not know what this means. I want to have one of my Dynon Skyview EMS pins watch for ground on a wire. If the pin does not see ground then the display annunciation will be dark however when the pin sees a connection to ground then the EFIS display will annunciate an “ICE” warning (it has to look for ground because I need to share this EFIS input pin with the Dynon AOA/Pitot tube heater system monitor wire. This monitor wire is open when the pitot heater system is working correctly however when the pitot heater system fails, the system connects this monitor wire to ground).
If the Dynon will sense a dry switch,
then some form of pull-up resistor is
included within the Dynon's signal
conditioning.
This makes your open-collector sensor
ideal to task . . . no additional
electronics required.
-This sensor has three wires: Brown “VCC”, Blue “ground”, and Black “output”. I assume the Brown wire needs to have a 5 to 12 VDC power source and the Black wire would go to my EFIS pin?
That would be my interpretation as well.
-I see where the “pull up resistor” is supposed to be installed however I do not know what value resistor to use or if it is required.
Not reqd.
-If the sensor relies on the magnetic attraction of the target magnet and the target magnet moves away because it is mounted on the door however still attached to the air box structure is a second magnet that is located only ˝ inch next to the sensor, will that second magnet effect the operation of the switch?
Maybe . . . easy to check on the bench.
No way to increase that separation?
-I want to use the Dynon Skyview PIN 18 as the power source for this sensor. PIN 18 is a 5 VDC power source that is output limited to 300 mA. I am already using that pin to power a McLagan Enterprises CS-6AB current sensor so I do not want to overtax the 300 mA output rating of the pin. Does anyone know what the current draw of the CS-6AB (it cannot be much)
. . . it seems unlikely that a 'sensor'
would need more than a handful of milliamps.
I think the risk is low.
A recap on the project…I built an air filter box out of fiberglass and it has a reed type valve alternate air that is made from fiberglass and is held closed by a fiberglass spring and two magnets (one on the door and one in the fiberglass air box structure). The design is such that should the big air filter become iced up the engine vacuum will pull against the door’s spring and the two magnets and open the door (one magnet will ride away because it is mounted on the door while the second magnet will stay attached to the air box structure). I want to monitor the position of the door with the Dynon EFIS pin input.
I think you're on the right track. Some
fiddling with the proposed magnets on the
bench should assuage concerns for untoward
interactions.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jun 14, 2017 5:09 am Post subject: MP100701 Open Collector To Ground Position Sensor |
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| Quote: | d
These magnets are like really... REALLY small and if I place them on one corner of the door (one magnet on the door and one on the air box structure) then there will be about 2.5 inches of distance to the adjacent corner where the magic switch can be installed... then perhaps there will be enough distance to reduce any magnetic interference. I will buy this sensor and conduct some fiddling around and report back. |
Ohhhh . . I thought the magnets were going to be CLOSE.
2.5" is like 'across the street'.
If they were, say 0.5" apart, there MIGHT be valid
interaction concerns to be resolved but 2.5" is plenty.
I don't recall now which 60's Cessna used a similar
alternate air door but the magnet holding it closed
was a rather pedestrian cabinet door latch. Gravity
would re-close the door. There were no annunciators
on that system. The door magnet doesn't want/need
to be very stout . . . pressure drop through a clean
filter is, by design, as low as practical . . . measured
in inches of water. You can calculate the force
offered by such differentials and use it to test the
release pressure of the finished assembly.
Just remember that the total force is spread out
over the door area and averages 1/2 the total
applied to center of the door (class 2 lever).
There is a boat load of magnet choices on eBay
including disks with countersunk holes for screw
mounting. http://tinyurl.com/ycoxy94d
A spring-force gage can be crafted to check
the door open calibration.
I think I'd encase the mounted magnet in a layer
of glass . . . while the risk is low, these things
do break and the particles are akin to crushed
carbide . . . not something friendly to engines.
Bob . . .
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billhuntersemail(at)gmail
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| Posted: Wed Jun 14, 2017 2:43 pm Post subject: MP100701 Open Collector To Ground Position Sensor |
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| Quote: | I thought the magnets were going to be CLOSE.
2.5" is like 'across the street'.
|
The flapper door is 4 inches long and 2.5 inches wide. Plan A (what is currently built) has a ˝ inch diameter magnet mounted in the middle of the 2.5 inch door frame…so not like across the street but in the same housing complex. These toothbrush magnets are very strong so perhaps I could install them on one corner and then the switch on the other corner.
| Quote: | I don't recall now which 60's Cessna used a similar
alternate air door but the magnet holding it closed
|
was a rather pedestrian cabinet door latch. Gravity
would re-close the door.
They stole my idea…HOW RUDE!!!
| Quote: | There were no annunciators on that system.
|
Sorta takes the fun out of it…Well I suppose their engineering budget was a bit more than mine so they would not really need a monitoring circuit. I could teach my cute little EFIS girl to say “MONITOR” when the door opens but I guess that might be too 2017…a “light” will do.
..
Cheers!!!
Bill Hunter
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Wednesday, June 14, 2017 6:08 AM
To: aeroelectric-list(at)matronics.com
Subject: Re: MP100701 Open Collector To Ground Position Sensor
| Quote: |
d
These magnets are like really... REALLY small and if I place them on one corner of the door (one magnet on the door and one on the air box structure) then there will be about 2.5 inches of distance to the adjacent corner where the magic switch can be installed... then perhaps there will be enough distance to reduce any magnetic interference. I will buy this sensor and conduct some fiddling around and report back. |
Ohhhh . . I thought the magnets were going to be CLOSE.
2.5" is like 'across the street'.
If they were, say 0.5" apart, there MIGHT be valid
interaction concerns to be resolved but 2.5" is plenty.
I don't recall now which 60's Cessna used a similar
alternate air door but the magnet holding it closed
was a rather pedestrian cabinet door latch. Gravity
would re-close the door. There were no annunciators
on that system. The door magnet doesn't want/need
to be very stout . . . pressure drop through a clean
filter is, by design, as low as practical . . . measured
in inches of water. You can calculate the force
offered by such differentials and use it to test the
release pressure of the finished assembly.
Just remember that the total force is spread out
over the door area and averages 1/2 the total
applied to center of the door (class 2 lever).
There is a boat load of magnet choices on eBay
including disks with countersunk holes for screw
mounting. http://tinyurl.com/ycoxy94d
A spring-force gage can be crafted to check
the door open calibration.
I think I'd encase the mounted magnet in a layer
of glass . . . while the risk is low, these things
do break and the particles are akin to crushed
carbide . . . not something friendly to engines.
Bob . . .
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