An Instrument That Stops Rotating Gives Shutdown Command To Machine

An Allen-Bradley "Speed Switch" does this, or similar. A proximity sensor detecting a lobe could also be combined with a time delay relay.

Thank you Tornado, i will check about this and get backsoon.

Hi, would you like to describe or elaborate what kind of machine is this? please give the details of the rollers (dimensions, shape, etc..)

thank you.

Hi,

this is a wire straightening and cutting machine. u can get the machine functionality from google. there are 5 roller attached zig zig position in the entering end. roller dia is approx 30mm. it is looking like a bearing shape.

right end of picture u can see the machine.

sorry i dont have the full view picture. actually the roller is not fully shown in this pic. i will try to take and upload soon.

something like the same

Two timers, one delay on energise, one delay one de-energise, will do the job. Attach a collar to the shaft with a projecting bolt or cam that gives you one pulse per revolution triggering a proximity or limit switch.

Wire both timers so the power is fed via the proximity/limit switch. Wire N/C outputs from both timers in series with the latching contact on the run circuit. Set both timers to a 5 second delay.

When the shaft stops, the proximity/limit will or will not be triggered. One of the timers will time out and break the circuit. On restart you need to hold the start button closed for one pulse to reset both timers.

American Mine Research has an LS300 "Little Speedy" switch that I use on conveyor belts, crushers, etc. It is powered by 120 volts, has an indicator light to let you know when it is working, and has adjustment for time and speed. Really easy to install and adjust. This switch works on change of a magnetic field. A target is needed such as a bolt or nut on the end of a shaft. It the shaft is smooth we sometimes add a hose clamp and utilize the adjustment screw for a target.

We have done this with a resolver attached to one of the center wheels. The outside ones slip so don't use them. The resolver is fed into a high speed counter in the PLC which can control your off on function. You can also use this for a rough indication of how long the wire is. Its fairly accurate but some slippage occurs.

I have done the same thing with an optical encoder. When the pulse train stops the program shuts down the machine,

Ron

Use a Whirligig on the end of a shaft, or slave drive a shaft off of a roller and Whirligig it.

www.go4b.com - or - http://www.go4b.com/usa/products/speed-switches/default.asp

I am not in any way aligned with 4B, but they have always treated me right, and the whirligig set-up is a cheap, easy way to be sure your equipment is always turning. It can also tell you if you get outside of speed parameters (either too fast or too slow). You can't build something yourself for the price they sell these things (pretty simple, really).

They have a magnetic mount, if you are turning slowly and have a mild-steel shaft. If you are spinning fast or have a SS shaft, you will need to tap a hole in the end center of the shaft and thread the Whirligig into the end of the shaft.

Add a switch or mechanical or hall effect sensor to the fixed part, make a simple "Missing Pulse detector" using say a NE555 chip or one of its many derivatives.

As soon as the object stops turning, the circuit will time out and give a signal......

Total cost of electronics probably around US$10.

Here is one:-

http://ecelab.com/circuit-miss-pulse-det.htm

hello andy,

to make missing pulse detector circuit using IC 555 integrated with hall sensor is not easy job because to handle hall sensor is itself a difficult job and to make circuit integrated with them is more difficult.

so, think about it gain and if it possible it is nice.

Its very simple nowadays, there are chips around to handle it for you. Look here for some great infos from Honeywell (one of many such companies!):-

http://content.honeywell.com/sensing/prodinfo/solidstate/technical/hallbook.pdf

Or simply use one of those IR LED in an enclosure with a IR Receiver and paint a white strip on the revolving part. Aim it at the shaft and it will give an output every time a white or shiny area goes by......use that as an input to that circuit I posted......

ITS ALL REALLY SIMPLE NOWADAYS!!!! Truly!

hello,

ya with ir led it is very simple to make but with hall effect i have a doubt till now because the link you are pasted tells that for shaft positioning we have to rotate the shaft in between hall vanes and placing digital output sensor which is quit messing and costly.

If you cannot achieve that, then do something else!

At the end of the day, you only need a signal that changes at least once every revolution, its really not rocket science......

Watch out with IR sensors and fluorescent lighting, they sometimes pick up the 50/60 Hz of the mains via them....which is why I prefer other methods of detecting!!

Watch out with IR sensors and fluorescent lighting, they sometimes pick up the 50/60 Hz of the mains via them....which is why I prefer other methods of detecting!!

I have also had problems with mecury vapor lighting or more specific the coating that is on the bulb. It puts out a wave in the 850 nm reigon(near IR) and can cause a signal input.

Ron

That 850 nm light sounds to be a significant part of the problem that I saw, I did not check for the type of light (I had nothing to test that with either), I only saw 50Hz pulses.....which screwed up the simple logic system that I had constructed.

I had honestly not give a thought to Fluorescent lights as it worked fantastic on the work bench which was lit with old fashioned light bulbs in those days.......DUHHHHHHHH

I had to build a simple filter for 50Hz to get it to ignore the light pulses.....It was a long time ago, I had almost forgotten!!

I could have used some sort of light filter to get the same effect!! (If I had known!!)and if such filters actually existed 20 years ago. (not my area of competence!)

You post is one of the many reasons that I SO like CR4.....many, many thanks.

This is what happened. We had built a P.I.G. to test the delta pipe ID. It was using the Sharp IR sensor that in stock state is only accurate to around 1 cm. We managed to increase the accuracy to +/- 1 mm. We were calibrating it aganist the floor and when we looked at the digital data there was a spike around 10 degrees off vertical around 10 degrees of arc. It was then my tech noticed the mercury vapor bulb that was around 10 degrees off. We rotated the unit, on the floor 90 degrees and the spike was not present

So ya hafta be aware that some wavelengths are on a bell shape and things like lasers are mono. We have gone to a 650 nm laser with an optical bandpass and are now getting +/- .001" accuracy with no interference from the lights.

Ron