In this video we’ll continue where the part II left off and look at Muting.
Muting temporarily disables the light curtain.
Maybe you have an area that’s protected, but every now and then a pallet of good needs
to leave the area.
The light curtain has some sensor inputs it can monitor.
You can then configure the light curtain to recognize that if an object approaches the
light curtain at just the right rate and from the right direction, so it knows it’s ok
to let the object through without tripping the outputs.
There is this L configuration which detects objects approaching from one direction and
a “T” setup which can detect objects approaching from two directions.
Were going to use a T configuration in this video using the companion muting bars that
have the sensors built in.
You don’t have to use these – you can use any sensors you want to initiate the muting
function.
The muting bars are just real convenient because all the alignment and spacing is already done
for you and wiring is also pre-setup when you use the companion cables.
You just plug it all together and you’re done.
I’m going to remove the blanking we did in the last video and then flip over to muting
just to keep things simple.
These first 5 items here are the exact same ones we did in Part 1 so we are not going
to repeat those here.
Here we set the muting direction and to do that we need to specify the configuration
T or L. L is simple, you have a pair of sensors.
Given those two inputs the Light Curtain can determine direction and speed of the approaching
object.
The T configuration can be setup like a double L or like this so it can detect objects coming
from either direction.
This alternate configuration allows you to set things up with only two sensor pairs –- but
it is really tedious to setup – you have to get all of these distances just right,
this crossing point has to be in just the right place, etc.
We’ll use this first setup today just because it’s easier.
It does require four sensors to operate, but it is so much easier to setup.
And while I’m using these convenient muting bars in this setup, you can use any sensor
you want.
You don’t have to use these.
These Muting Arms literally just have a pair of optical sensors in them at a known spacing.
You can see where the sensors are if I run my hand through here.
This T12 is the time it takes the package to go from the A sensor to the B sensor which
is how fast the package is moving.
You are specifying the max time here which indicates the slowest velocity which will
invoke the muting.
Since we have two sets of sensors in this T configuration, we know when the package
has finished passing through the light curtain.
We don’t have that luxury with the “L” configuration.
So instead we just specify the width of the muting signal in multiples of the time it
takes the sensor to pass between the two sensors.
This “m” value is that multiplier that is only available in the L configuration.
Since muting stays active as long as both muting signals are active, we need a way to
detect that they are stuck.
We can force the muting to time out after some length of time here.
We can also say we want muting to stay on forever once it is triggered.
Enabling the muting filter helps reduce false triggers from noise on the muting signals.
The override can be level or edge triggered.
You would want level triggered if you want someone to literally hold a momentary button
down.
If you want just a momentary button press to enable muting so you can walk away then
you’ll use this one.
And you can specify a timeout for the override too.
Normally the entire Light Curtain is muted when the two muting inputs are sequenced correctly.
You can also specify that muting only affects a portion of the light curtain.
Maybe boxes on a conveyor only use the bottom third of the light curtain – you can leave
the top two thirds active to help increase the integrity of your safety system by only
muting the bottom third of the light curtain.
This is just like the example we did in the previous video.
You can add a muting zone with this plus sign.
You can stretch it, shrink it, add a zone above this zone, add another zone below this
zone.
Just like before you can have up to 5 zones.
And you can also teach the partial zone.
I’m going to turn off partial muting for this demo and just use full muting.
Let’s send this configuration to the Light Curtain.
We want to write it out.
Yes we really want to confirm that.
When you see this save button you know it’s done.
Let’s try it.
Remember, we set this up so that the max time between here and here is 4 seconds, so we
have to move faster than that to initiate muting.
Also, the sensor spacing is critical.
The key thing to remember is the object that you want to mute on has to be longer than
the distance between A1 and A2 or B1 and B2.
Let’s switch over to the monitoring view so we can see the status lights.
So if I move my hand through here
which is smaller than this distance , the light curtain output signals trips and shuts
down the machinery.
But if I have a large pallet of stuff moving into the area
that is longer than this distance it passes through the light curtains without tripping
the output signal.
Exactly what we expect.
The light curtain saw the large object coming and muted itself so it could pass.
Perfect.
So muting is ideal when you want to prevent fingers, hands or even bodies from entering
an area, but still want large pallets of stuff to pass through without shutting down the
machine.
Well, that ought to be enough to get you up and running with muting.
If you have any questions, contact AutomationDirect’s free, award winning tech support during regular
business hours.
They will be happy to help.
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.