A quick measure of the picture shows the shuttle makes between one half and one revolution as it travels it's length. That alone is enough to cause the rod magnet idea to fail more often than it works.If the shuttle is spinning then you will get multiple pulses per quarter rev. If stationary then you will get one.
Mike.
[snip}
Rolf,
The mirror is mounted on a surface with a HOLE across the surface, when any string of any shuttle is cut off or finished then the surface has no support (leakage of the taut string) and will be exposed due to centrifugal force. Make sense?
Wish I could open the ZIP'ed video clip, maybe I would understand what is going on better.
Rolf
A quick measure of the picture shows the shuttle makes between one half and one revolution as it travels it's length. That alone is enough to cause the rod magnet idea to fail more often than it works.
Dan
hi LC,
Like your magnet idea, my thought would be if you fit say 3 magnets to the shuttle will the 'metallic' parts of the main assembly cause drag on the shuttle due to the magnetic interaction.?
I am not being fixated, I am a design engineer that knows the pitfalls.Don't get all fixated with the solution proposed.
I have said to use one magnet, but there is the possibilities to fix two with 180 degrees or even three at 120 degrees apart. If the shuttle is rotating along its axis that slowly.
The microcontroller just counts how many pulses per one whole revolution of the loom and keep a running average of the pulses count.
Any accumulated count per loom revolution of 75% or less would means one shuttle has stopped rotating. It is easy to set the trip point at 80% that of the current running average per loom revolution.
Recharging or replacing 4 AAs every three months would be a bother?Ubergeek63,
The factory does not like to be involved with replacing or charging the batteries.
I am not being fixated, I am a design engineer that knows the pitfalls.
In this case you are talking about beat frequencies, or in layman's body of experience, the strobe effect. A fan blade in the sun is a blur. A fan blade in AC lighting shows a distinct number of blades, the number seen is the multiple of the frequency of the light source that the blade is spinning at.
The same thing will happen with the magnet on the shuttles. At certain spool diameters the sensor will completely miss the spinning and shut down his loom. It might be alright for a hobbyist, but that is production equipment and time is money. And that is the reason for the initial query: to save the time and materials when the shuttle runs out while your back is turned.
Dan
I believe you are confused as to the geometry of the thing. They are making bags not socks. If we assume a 1M diameter you are talking about one pulse for between 7cm and 30cm of shuttle motion. Do you think a coil of that size, assuming it is sensitive enough, is practical?This is a very good point and one I hadn't considered. However, this will only happen if the shuttle does less than one revolution as it passes the sensor. Looking at the pictures it looks like the shuttle is (at least) 5 time smaller than the central hub and so it should do 25 revs per orbit. A correctly sized coil should pick up multiple pulses.
Mike.
Straight ratio, there is no square term in the circumference. 1M×PI around the sack and 1-3CM×PI around the shuttle.Think metal detectors. Pulse Induction metal detectors induce a current in the target object and then look for eddy currents. They work reliably at 12". With a magnet providing the pulses it will be relatively simple.
My assumption on the geometry is that the shuttles provide thread that goes around the sack hence my assumption that the relationship between the two speeds is the square of there diameters. How can a shuttle go around a hub and not provide enough thread to match the circumference?
Mike.
Which means you 15CM of sensing to ensure that you do not miss a pass. Combine that with the possibility of receiving anywhere from one to four pulses as the various shuttles pass the sensor becomes a bit of a math problem, if you're lucky.Yes, my bad, a straight relationship. From your guesstimate that would still result in 30 (to 100) revs of the shuttle to one revolution around the machine.
Mike.
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