IFM Electronics

mae · May 31, 2012

I am using 6 IFM lasers that I have mounted about 12' above the belt that I have looking about every 3" across the width of a belt to detect if a log is on the belt on not. They work great in the mornings, but as soon as the sun breaks over the building and starts shining on the spot they are looking at, they become completely unreliable. While we are running the sun is never actually looking into the lenses of the lasers. It seems to just be where the lasers are looking at. I am using the O1D100 and am using the OUT1. Nothing fancy, just if one of the lasers is made then if says a log is present. I figure that I have a parameter that is in the wrong position, but after reading the manual, I still am at as loss.

The belt is a blask rubber belt, I;m using a PLC5. I not sure what else information that would be helpful.

Again thanks for the help!!

Mikey

Tharon · May 31, 2012

Large sources of light can interfere with photo sensors. The sun being a very large source. You will want to limit the amount of sunlight reflecting off of the surface you are trying to detect and the amount that the sensor would get directly.

According to the manual for the O1D100, it's a bit more than just a standard "present or not present" photo sensor. It measures distance and has a programmable output.
http://www.ifm.com/mounting/704991UK.pdf

MarkNightingale · Jun 1, 2012

As Tharon says you can program the sensor.

The first 2 settings I would look at are the hysteresis and the damping. Remember to set these when the sun is shining.

The other option you have is to use both outputs from the sensor. Use one for when it is dark outside and the other when it is light. This way you will always get an accurate signal from the sensor.

Mark

mae · Jun 6, 2012

"The first 2 settings I would look at are the hysteresis and the damping." I found the hysteresis in the book, but I'mm not sure that the damping is. I really like the sensors, And in the morning they are great, but I just can't make them woek when the sunlight is on the belt. Any more help would be appreciated.

wimpiesplc · Jun 6, 2012

maybe you want to try another angle towards the belt. this is common practice when detecting glossy materials like sheet metal. try to get away from the reflection of the sun (or try to block it).
do you really have to look at the belt? can't you look to a reflector next to the belt, for example?

shooter · Jun 7, 2012

way overpayed and not suitable for this belt.
Do it with a laserdiode on the start of the belt and one on the end of the belt, you only need one set. Have the sensor in pulses so it blocks out the sun.

mae · Jun 19, 2012

I'm not actually looking at the belt all I am wanting to know that if there is a log on the belt or not. And yes I payed dearly for them but for the application and the payback it will be worth it. The logs are not always in the same place so it's not as easy as putting a sensor on the front and one on the end. I'm trying to estimate when the log will be out of the way so that I can get another log on the belt as quick as possible. Thanks for everybodys help!

WainDude · Jun 19, 2012

Paint the belt a different color, even if the paint flakes off, it will cut down on the reflection. Knowing IFM, they will have a way to cancel out the effect of the sun. And yes, these are way to high tech of a solution for such a basic application.

Good luck

WainDude · Jun 19, 2012

Another solution, take one of the lasers off the mount and place it beside the belt so it is facing across the width of the belt at a height suitable to detect your logs, that way there will be no interference due to reflection on the belt. since this is a laser distance sensor, you can set the output to trip at a preset distance.

shooter · Jun 20, 2012

aha so you want the position of the logs on the belt?
yes paint the belt red.
have a look at a keyence sensor, they give aheight registration of the product, then you know exactly where each log is.
same can be done with a simple camera above the belt and recognition software on a PC.

mae · Jun 22, 2012

I covered the belt with a tarp so that I can justify putting a roof over it. If I am able to justify this I will be installing a Cognex camera above the infeed so that I can get the gap the best it can be. That is what I have wanted to put on it all along but with the sun, I was worried about it working. Thanks for everybody's help!!! I have the lasers at the top of the stepfeeders but I really want to try and make the Cognex camera work. I would then be able to measure the logs while they are still on the top of the stepfeeder and hopefully put them end to end. I enabled the lasers today with the tarp over it and had to put a timer on it because it was putting them closer then the machine could handle. That's what I want. Everyone has been great with all the help. The is alot of very smart prople on here. Thanks everybody!

mae · Jun 22, 2012

I don't want to move any of the sensors due to the harsh conditions that it would introduce. But thamks anyway!

mae · Jun 25, 2012

Here is the logic that I am using for the IFM lasers. They are still double feeding logs into the belt that they are looking at. Anyone see anything wrong or any improvements with this logic?? Thanks MAE

mae · Jun 25, 2012

Looks like it didn't upload, so I'll try it again.

bce123 · Jun 25, 2012

I am thinking large flapper attached to a limit switch. when the log passes under the flapper it makes the limit switch and you logic prevents another log from loading. then use the laser from under the shade of the flapper to measure the travel of the flapper to determine dia. of the log. add an encoder to the conv. to get length. calculate the board feet and optimum cuts with your PLC ect...........

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