photoelectric sensors light on / dark on

[tragically1969]

The conveyors are like solid rubber coated belting - so no looking up from below.

And yes, they don't want reflectors so not sure if the proxy I have chosen would work without one.

Above placed sensors would not work as these bases are big and they throw them on high endways sometimes - not to mention the gantry to build for 11 sensors

If you are in the UK (think you are ?) give the guys at IFM or LCA in Blackburn a call, LCA deal with SICK

 

[adisharr]

A top mounted ultrasonic would work using the conveyor belt as a background and would be very stable.

There are a few lines but Schneider Electric (Hyde Park Ultrasonics) has a 900 series - 2m range (30mm barrel) that can be set to 'background mode' where you would then teach a small window around the belt. Anything that causes the sensor to not see the belt in the taught window will give you an output. Trying to bounce an ultrasonic signal off of the mattress base itself isn't going to work well unless the side of the base is perpendicular to the sensor within about +-5 degrees. The sensor are around $ 500.00. I've been using the line for 15 years.

A high gain diffuse background suppression sensor will also work although retro-reflective and through beam units are always preferred but sounds like that's not going to be possible here.

If you have any slots in the belt, you can mount an under-conveyor sensor.

 

[tragically1969]

Anything that causes the sensor to not see the belt in the taught window will give you an output. .

But that just ends up being the same as a through beam all be it ultrasonic ?

I am guessing that's the exact reason a through beam is not an option over a close range proximity, operators getting in the way and breaking the beam ?

 

[adisharr]

But that just ends up being the same as a through beam all be it ultrasonic ?

I am guessing that's the exact reason a through beam is not an option over a close range proximity, operators getting in the way and breaking the beam ?

Well it would be top mounted which would be out of the way and require no target other than the conveyor belt itself.

It was my impression that a side mounted orientation would not work with a target or reflector because that would interfere with operators loading the bases onto the conveyor.

If the bases have holes then that might be an issue.

 

[Gomez_]

I would recommend something like the IFM OID200: http://www.ifm.com/products/us/ds/OID200.htm

Its a laser time of flight sensor, NO and NC PNP outputs, and you can set the trigger distance.

EDIT List price is $140 in the US catalog

 

[adisharr]

I would recommend something like the IFM OID200: http://www.ifm.com/products/us/ds/OID200.htm

Its a laser time of flight sensor, NO and NC PNP outputs, and you can set the trigger distance.

EDIT List price is $140 in the US catalog

That has some odd requirements for background suppression.

 

[Gomez_]

That has some odd requirements for background suppression.

Could you be more specific, I'm not sure what requirements you mean?

 

[adisharr]

Could you be more specific, I'm not sure what requirements you mean?

It mentions something about an ambiguous output if you have a background target >20m away. It's probably due to the TOF system timing generating false outputs. That happens on ultrasonics in certain modes as well.

 

[Gomez_]

It mentions something about an ambiguous output if you have a background target >20m away. It's probably due to the TOF system timing generating false outputs. That happens on ultrasonics in certain modes as well.

Oh, that makes sense. Its only rated up to 20m distance.

 

[shooter]

i would paint a piece of the belt white, or any color not used by the matras.
put the sensor on the white piece, if a matras is on the belt you can detect it.

 

[Ronnie Sullivan]

Thanks for the replies.

In the end (and in most cases) money was the winner.

Reflectors with nice protective and solid covers were fitted. (They were fitted very low - just peeping over the belts)

The original photoelectric sensors worked perfectly with them even though in the spec they had a 'seeing' distance of 0.4 meters. But, that's without reflectors I suppose - no distance was specified for that.

The funny thing was; nobody could understand why I had to spend time reversing the logic for every instance of the sensors in the program.

 

[adisharr]

Thanks for the replies.

In the end (and in most cases) money was the winner.

Reflectors with nice protective and solid covers were fitted. (They were fitted very low - just peeping over the belts)

The original photoelectric sensors worked perfectly with them even though in the spec they had a 'seeing' distance of 0.4 meters. But, that's without reflectors I suppose - no distance was specified for that.

The funny thing was; nobody could understand why I had to spend time reversing the logic for every instance of the sensors in the program.

Just a heads up, you may run into some issues as the original sensors are not designed for reflectors. Retro-reflective sensors have a polarizing filters over the transmitter and receiver lenses they are 90 degrees out of phase with each other.

When the beam exits the transmitter, the light is filtered into one plane, bounces off the reflector (which flips it 90 degrees) and allowed to enter the receivers filter. This allows detection of even very shiny surfaces without false signals (mirrors, shiny metals, etc.)

You might not see any issues but if you do you might want to replace the sensors with a true retro-reflective type.

Glad you got it working through

 

[Ronnie Sullivan]

As stated: the sensors are looking across the belts, not from above.
I thought system integrators considered a problem then came up with an original solution.
Paint a white line!, really.

 

[silva.foxx]

It aint correct but it works.

Why not buy the right sensors with the refund from the project company bailing out?

 

[Badger]

Ron pm me I may be able to help.