Can't Buy Sensor for Stirling-Steel CNC Conversion

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Bob D.
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by Bob D. » Thu May 22, 2014 10:35 pm

hammermill wrote:These can also work well for for travel safety / stops
I don't agree with this. Overtravel switches should be Normally closed mechanical micro switches. Proxs aren't as reliable for this application. Never see them in industry equipment used as overtravel devices. There are good reasons for that. I suppose if the machine can't possibly damage itself or you a prox can be used.

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SteveHGraham
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by SteveHGraham » Fri May 23, 2014 10:31 am

This thing is going to cost me $22, which is a lot for a switch, so it is not likely that I will be using the same technology as an automatic shutoff.
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by ken572 » Sun May 25, 2014 6:48 am

SteveHGraham wrote:This thing is going to cost me $22, which is a lot for a switch, so it is not likely that I will be using the same technology as an automatic shutoff.
Good Morning :!: Steve :D

If you enjoy playing around with electronics, you could

build and package these (Listed Below) yourself

Super Cheap. :wink:

http://www.allelectronics.com/make-a-st ... sor/1.html

Just a thought :idea:

Ken. :)
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from working with the older Masters.
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by SteveHGraham » Mon May 26, 2014 2:37 pm

Is that what's inside this thing? I have no idea.

I took electronic courses while getting my degree, but it was pretty basic. Although there was a lot of calculus in the explanations of the circuits. Just like physicists. Make it hard but useless.
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by Rick » Mon May 26, 2014 6:38 pm

SteveHGraham wrote:Is that what's inside this thing? I have no idea.
Not really, what Ken shows is a Hall effect sensor, They switch due to the presence of a magnetic field. These are used for many things and require a magnet to make them change state, air cylinders make extensive use of this style. The piston on the cylinder has a magnet and the sensors are mounted outside the body and are used to sense position of the piston (extended or retracted) Steve what you specified was an inductive prox switch. These do not need a magnet but look for a disturbance in the field they produce. These switches will change state when something comes close enough,to them to disrupt their field. ie the reason for the 4mm sensing range. They will sense non magnetic material but not as well as magnetic ones.

My description may not be 100% but the basics should be oK
Rick

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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by hammermill » Mon May 26, 2014 7:13 pm

http://www.pidtechinsights.com/2012/03/ ... ns-part-1/




http://www.pidtechinsights.com/2012/03/ ... selection/
A little data from PanAsonic sorry the tabs were in reversed order


one thing not mentioned is the current capacity of the unit, some i have seen were as low as 200 ma other have a set of dry contacts that will handel a amp or so. the world of sensers today offers lots of options.

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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by SteveHGraham » Mon May 26, 2014 8:44 pm

Rick wrote:Steve what you specified was an inductive prox switch. These do not need a magnet but look for a disturbance in the field they produce.
Now that I think about it I remember that it was described as inductive.
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by WJH » Fri Jun 13, 2014 7:04 pm

The CRJ I fly has those inductive proximity sensors all over the place for detecting doors open or closed, landing gear position, thrust reverser position, etc. I imagine they are a bit more expensive than 22$!

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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by SteveHGraham » Mon Jul 14, 2014 2:38 pm

Working on the lathe today. I have been reading the manual once again, trying to get a clue.

The purpose of this sensor is to keep track of the spindle's position, for threading and so on. It will be inside the lathe's headstock housing, aimed at the butt end of the spindle. The plans call for a steel flag to be attached to the spindle, and the sensor detects the flag by induction, I guess.

The flag is a scrap of steel the size of a postage stamp. The plan is to put a screw into the spindle, through the flag, and the screw will hold the flag in place when the spindle is moving.

My obvious question: do I really need a steel flag? I am not sure how a tiny piece of steel on a spindle will cause induction, since the spindle is steel anyway, but I have to wonder if this is the best way. I have a bunch of reflective flags (adhesive) for a handheld tachometer, and they were less aggravation to install, since you just peel and stick.

I don't see how a rectangular flag and an on/off sensor can tell the machine where the spindle is. I can see how it would give RPM info. The plans say it will enable me to do threading. I'm sure it works, but it sounds weird.

I am going to have to look at controllers before I buy to make sure this thing will plug into them.
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by ctwo » Mon Jul 14, 2014 4:18 pm

Is it magnetic induction?

The system will be able to pick up the TDC "pings" and interpolate position between the pings based on the time it took during the previous cycle and an assumption that rotational velocity has not changed during the current cycle.

Controller?
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SteveHGraham
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by SteveHGraham » Mon Jul 14, 2014 4:23 pm

The only kind of induction I've heard of is magnetic, unless you count being drafted.
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Re: Can't Buy Sensor for Stirling-Steel CNC Conversion

Post by hammermill » Mon Jul 14, 2014 7:22 pm

As the flag passes by it upset s the field generated by the sensor
That
Does it

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