Author Topic: Detect presence of a thin wire  (Read 5023 times)

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Offline alan.alanzhang@gmail.comTopic starter

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Detect presence of a thin wire
« on: September 29, 2023, 04:01:18 am »
I have a small gap (5mm-10mm) where a thin Nitinol wire passes through. I'd like to detect the presence/passing through of the Nitinol wire with a sensor. It can be contactless or a contact based sensor. The wire could make direct contact with the sensor but only at the sensor so it doesn't form a complete circuit (the wire dangles from a quad copter drone in mid air while the write enters the gap).

Ideally the sensor detects in under 100ms.

Thank you in advance.
 

Offline Dan123456

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Re: Detect presence of a thin wire
« Reply #1 on: October 01, 2023, 07:14:46 pm »
Would a photo interrupter work?

They are basically an IR LED and IR receive in one and will give 6ou a signal is something blocks the gap.
 

Online dobsonr741

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Re: Detect presence of a thin wire
« Reply #2 on: October 01, 2023, 07:35:44 pm »
A sketch would be helpful to understand the wire’s position and also to tell why the wire would not be there, or move out of position. Just to avoid becoming a XY problem https://xyproblem.info/
 
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Offline Marco

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Re: Detect presence of a thin wire
« Reply #3 on: October 01, 2023, 07:49:39 pm »
IR reflection sensor would be my first pick if it had to be done with minimum engineering.

Capacitive sensing would have the advantage of not responding to non conductive debris.
 

Offline Infraviolet

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Re: Detect presence of a thin wire
« Reply #4 on: October 01, 2023, 08:09:16 pm »
As the wire is thin any IR transmission gap sensor would liekly need to be sensitive with an analogue output, to detect a drop in intensity as the wire crosses rather than a total blocking. Whether reflective IR could work will depend on how shiny the wire's surface finish is.

You want to avoid any sensor that could cause a complete circuit, does that mean a current is running in that wire between the drone and somewhere else, or that the wire is held at a particular voltage? Either of those possibilities would open up more sensing possibilities, Hall sensor ifa current is flowing for example.
 

Offline MarkF

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Re: Detect presence of a thin wire
« Reply #5 on: October 01, 2023, 08:37:10 pm »
This may be a little unorthodox...

Would you be able to fit a strain gauge to sense whatever you're going to hang from the end of the wire.

I have not worked with strain gauges; so I don't know the range of weights they can detect or what kind of output they have. 
I just saw that the new Prusa 3D printers detect zero Z-height with a strain gauge mounted on the corner of the bed instead of a micro-switch.  Which is where I got the idea from.
 

Online themadhippy

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Re: Detect presence of a thin wire
« Reply #6 on: October 01, 2023, 09:23:04 pm »
would something along the lines of a metal detector work
 

Offline jpanhalt

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Re: Detect presence of a thin wire
« Reply #7 on: October 01, 2023, 10:42:27 pm »
How thin is "thin?"

If thick enough, I second the IR reflection method.  That is what used to detect the position of a 1/8" (3 mm) thin wire on a device I made several years ago  It's very simple, and I have never had a false detection even in bright sunlight.
 

Online Circlotron

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Re: Detect presence of a thin wire
« Reply #8 on: October 24, 2023, 12:34:11 pm »
Have a look at a toroid winding machine. Some have a sensor that counts how many times the wire passes through a gap.
 

Offline jonpaul

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Re: Detect presence of a thin wire
« Reply #9 on: October 24, 2023, 12:52:09 pm »
Wire size: AWG #32?
40?
50?

See cat pages from MWS for wire tables /metric etc.

https://mwswire.com/

Jon
Jean-Paul  the Internet Dinosaur
 


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