Detect presence of a thin wire - Page 1
Forum section: electronics / general

author: alan.alanzhang@gmail.com
author_rank: Newbie
timestamp: September 29, 2023, 04:01:18 am
content: 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.

author: Dan123456
author_rank: Regular Contributor
timestamp: October 01, 2023, 07:14:46 pm
content: 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.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: October 01, 2023, 07:35:44 pm
content: 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 problemhttps://xyproblem.info/

author: Marco
author_rank: Super Contributor
timestamp: October 01, 2023, 07:49:39 pm
content: 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.

author: Infraviolet
author_rank: Super Contributor
timestamp: October 01, 2023, 08:09:16 pm
content: 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.

author: MarkF
author_rank: Super Contributor
timestamp: October 01, 2023, 08:37:10 pm
content: 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.

author: themadhippy
author_rank: Super Contributor
timestamp: October 01, 2023, 09:23:04 pm
content: would something along the lines of a metal detector work

author: jpanhalt
author_rank: Super Contributor
timestamp: October 01, 2023, 10:42:27 pm
content: 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.

author: Circlotron
author_rank: Super Contributor
timestamp: October 24, 2023, 12:34:11 pm
content: Have a look at a toroid winding machine. Some have a sensor that counts how many times the wire passes through a gap.

author: jonpaul
author_rank: Super Contributor
timestamp: October 24, 2023, 12:52:09 pm
content: Wire size: AWG #32?40?50?See cat pages from MWS for wire tables /metric etc.https://mwswire.com/Jon