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Distance sensor for diameter compensation

Distance sensor for diameter compensation

Distance sensor for diameter compensation

(OP)
We have in operation one re-spooler machine to wind welding mig wire on 15 kg plastic spools

The machine consists on a un-winder, a dancer unit and a winder

As the unwinder gives wire to the winder the diameter of the wire coil decrease. To compensate the diameter reduction there is installed a sensor (see picture attached)

The sensor is very old and it was custom made for it. I am not sure what kind of sensor is, but I am guessing is an ultrasonic sensor

The signal from the sensor is unstable (it varies +/- 1V ) while the coil is spinning and this is making the speed syncronism between winder and unwinder to become unstable too
My first thought was that the problem was a signal interference through the cables so I made a few measurements and the signal is coming unstable from the sensor it self

Is an ultrasonic distance sensor good for this application?
Is there another type of sensor that will not be affected by the spin of the wire coil?

Any help will be apreciated

RE: Distance sensor for diameter compensation

Ultrasonic is very common for diameter/acceleration compensation. It works well for papr and foil where the sensed surface is smooth. I have never used ultrasonic on wire spools, the dancer is usually able to do a decent job without the compensation.
If your spooling process takes long time in comparison to the drum speed, you should be able to filter out the variations with a simple first order lowpas. I would try a 10 k resistor and a 100 uF capcitor. You may need to experiment with other time constants or something else if your signal is a 4-20 mA. But still - a low pass filter usually works qute well.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

(OP)
Thanks Skogsgurra
I will buy those components and make a Low Pass Filter and see what happends

RE: Distance sensor for diameter compensation

If the sensor you are referring to in the center of picture is using ultrasound, then I would expect it to be measuring distance to copper wire on reel and not rotation speed. There may be a sensor on the left side of the photo that measures speed.

Walt

RE: Distance sensor for diameter compensation

We are talking diamater already. No need to confuse. It only attracts nebulous comments.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

"It only attracts nebulous comments."
My apology!
Walt

RE: Distance sensor for diameter compensation

(OP)
The sensor is for distance only. The speed of the unwinder is sense by a tachogenerator on motor´s shaft

RE: Distance sensor for diameter compensation

No probs, Walt.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

(OP)
@Skosgurra. If the sensor if faulty and sending unestable signals.
The filter will stabilize those signals?

RE: Distance sensor for diameter compensation

Probably not. A faulty sensor seldom outputs a correct mean value with superimposed noise.

The filter removes fast variations that the uneven coil surface causes. Nothing else.
It is very easy to find out if the sensor works correctly. Direct it towards a smooth surface and measure output as a function of distance. If the sensor is healthy, you will get a linear characteristic.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

(OP)
Thanks. I did the test and the sensor is working correctly. Is the uneven surface that is causing unstable readings

RE: Distance sensor for diameter compensation

Did you also test with a filter?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

Couldn't open that file. Try the "Upload image" in the tool bar.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

(OP)

RE: Distance sensor for diameter compensation

Thanks, Keith!

Was AFK for a while.

A 100 uF capacitor is almost certainly an electrolytic one. Make sure that you get the polarity right.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

(OP)
I have confirmed that the sensor is working good. The problem is the uneven surface of the wire reel
I put an empty reel. Made the unwinder spin. The output of the sensor stays on same value. No more unestable reading

I could not try the low pass filter yet because we just run out of wire. We will receive it next week

The components I have to build the filter are:
resistor: 10k ohm - 1/4 watt
capacitor: 100uF - 25 V

picture attached

RE: Distance sensor for diameter compensation

That should mush your signal into about a 1/2 to 1 second average that should swamp the dithering out completely. Hopefully you have a voltage out sensor and not a 4-20mA one.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Distance sensor for diameter compensation

(OP)
Yes, The sensor output is 0 - 10V but the voltage range that it is used is:

Full reel: 2 V
Empty reel: 7,2 V


RE: Distance sensor for diameter compensation

Thanks for checking that.

Those values are still a great place to start and likely will do the trick for you.

Let us know how it works out!

Keith Cress
kcress - http://www.flaminsystems.com

RE: Distance sensor for diameter compensation

Your originally noted variation in readings seem large compared to your full scale values, i.e., ~20%

The resistance and capacitance values mentioned above result in a 1 second time constant, so you need to be careful about whether the time constant is compatible with the timing of how the transition from one layer to the next is detected.

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RE: Distance sensor for diameter compensation

(OP)
Just finished the test with the L-P Filter. The signal from the sensor is much more stable now but I want to stabilize it a little more
Now the signal oscillation is +/- 0,3 V

Should I used a bigger cap? 150 uF? 200 uF?
Resistor used is 10k

Process speed performance has improved a lot!



RE: Distance sensor for diameter compensation

Yes, increase. The 1 second time constant was just an informed guess. Nothing beats reality - so increase until it looks good.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

(OP)
Tried with a 220uF cap and now the signal is very unstable again. I think even worst than without the filter! Not sure what is going on. I think I am going back to the 100 uF cap

RE: Distance sensor for diameter compensation

Sounds like you are getting too near the phase margin. Sometimes, you have to accept what you get.

How did the problem start? Did it ever work well?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Distance sensor for diameter compensation

(OP)
It was an used machine when we got it. A little after we bought it, I have to update the controls: old analog DC drives and analog control boards. I have installed new drives and a PLC. I also have to installed a dancer PID control board

Did it ever work well?
I am not sure. It took me a lot of time to get the machine to work. Specially to calibrate the PID control. Now I think that 50% of the problem was the signal from the distance sensor. I did not notice back then

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