In this video we’re just going to pick up right where the previous video left off – Resolution
and blanking.
Reduced resolution is one kind of blanking where objects can interrupt one or more beams
without the light curtain leaving normal operation.
Right now we are using all of the beams and have full coverage.
This box up here tells us for this light curtain we can detect any object that blocks more
than 29 mm of the light beams.
Which makes sense because if you look at this chart, you see the light beams are spaced
a little less than 20 mm apart.
So to ensure that at least one beam is always blocked you are going to need an object that
is about 50 percent bigger than the width of one beam, hence this 29mm number.
Given that we have full coverage and this qualifies for a hand safety class.
If we change this to a “1” we’re telling the light curtain to allow any objects that
intercept up to 1 beam to pass – the light yellow bars shown here represent the active
beams – we see that while the light beams can do 29 mm, by reducing the resolution by
1, we can now only guarantee detection of a 48 mm object and we have reduced this sensor’s
safety class to body.
If we change this to a “2” - here’s the on beam, here’s the off beams – now
objects can interrupt 2 beams without tripping the light curtain outputs.
We can also scroll to see the rest of the sensor beam layout.
Let’s increment this one more so now objects can interrupt 3 beams without the light curtain
changing from Normal Operation.
Let’s write this out to the light curtain.
The software asks us one more time – are you sure.
We are … And when that is done you can save and print
the configuration.
Once you have done that you could go up here to monitoring to test the result but since
you almost always want to do that, there is a button right here which takes you right
to monitoring.
And sure enough, since I only have 1 of every four beams working, if I run my calibrated
test rod up and down the sensor I see the beams being blocked but my output doesn’t
respond because the object has to be larger than 4 beam widths to get a response.
If I do run a larger object through then I do get a response.
Also notice that the sensor resets automatically when I remove the object – exactly what
we expect.
Let’s go back to configuration, double click on the dongle, select the light curtain we
want to configure – we only have the one– and we see our configuration.
So, resolution determined how samll of an object we could detect.
Blanking says ignore certain beams.
Maybe you have a fixed part of a machine that will always be blocking one or more sections
of the light curtain.
You can just turn off those beams – or blank those beams.
Resolution has to be zero to do this, so lets change that back.
To add blanking, just hit this plus sign.
This part of the light curtain is now blanked out.
You can stretch and move the blanked zone to any place you want.
The numbers over here show you what you have and you can adjust the blanking here too.
To add another blanked out area above this area click this plus sign, to add one below,
click on this plus sign.
You can have up to 5 blanked areas on a light curtain.
To delete a blanked area, just select it and hit the X.
You can also add a position tolerance.
Maybe you know a machine part only blocks these two beams but it moves around a bit
due to vibration.
This says this obstruction can move up or down one beam with out setting off the outputs.
Or maybe the blockage stays in one place, but changes in size.
Specify that dimension tolerance here.
In this case say you set aside 3 beams for blanking, but one beam on either side is set
aside for variations on the blockage size.
This is particularly helpful if you have something blocking part of a beam and vibration is enough
to block and unblock that beam.
Just up the beam count and add a dimension tolerance to tell the system those areas may
be flakey.
Note that when you change tolerances like this it changes the resolution of your system,
so be careful about that.
Can you do position and dimension tolerance at the same time?
Sure!
This says the object is one of those borderline sizes – it may or may not interfere with
the beam - and it may move around a bit.
Ok, let’s turn those off and look at some of these other options.
You can set blanking up to only have tolerance on the bottom, or only on the top.
You can see the little arrows on this icon change to indicate what the obstruction is
doing.
You can also tell the sensor that this blanked area can move around or float within the light
curtain area.
If you use this you have to make sure the blanked areas never leave the sensor field
of view or the outputs will switch.
If you have more than one blanked area they all have to move together in concert and maintain
their relative spacing and stay with in the field of view when using total surveillance.
Floating blanking with partial surveillance allows you to set this guy to float while
the others are fixed.
He can even cross though the fixed blanked zones and leave the field of view.
There’s a teach button here where you can have the sensor identify where the blocked
zones are and then add any tolerances you want to that.
The key thing to remember with fixed blanking is once you set it up, the sensor is always
going to expect that blockage to be there.
If the blockage goes away, the outputs will switch to safe mode.
And remember – at the end of the day it doesn’t matter how capable these light curtains
are.
Your system safety depends entirely on how you set these up and how you use them.
So please take the time to read through the user manual and learn all of the different
nuances of these various blanking modes.
If you need any help please contact AutomationDirect’s free award winning tech support during regular
business hours.
They will be happy to help you.
And don’t forget the forums!
There are lots of folks there that love to share their years of experience.
Just don’t post any questions directed at AutomationDirect’s support team there, they
don’t monitor the forums on a regular basis.