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Break Beam Sensor Integration
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Break Beam Sensor Integration

by Agrod on Tue Jun 16, 2020 5:07 am

Hello,

For a current projet, I need to trigger an event when a goal is scored in a table football game.
For that, I use 3mm IR BreakBeam sensors which are placed on the goal walls. The sensors are connected to an arduino nano through twisted cables.

The system seems to detect well the goals, however in the case of vibrations on the table, it also seams that goals can be detected.
Since the sensor LEDs (and photodiode) are passing through the goals walls through some small pierced holes, I suspect that these holes have a too small diameter and that it somehow obstructs and narrow the sensor beam, making it over sensitiveto vibrations.

Thus I wonder, if my hypothesis is correct, what minimal hole diameter I should have for the leds ?
Alternatively, even if the goal size is 22cm approx, would it be necessary to go for a 5mm sensor ?

Regards

Agrod
 
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Joined: Tue Jun 16, 2020 3:39 am

Re: Break Beam Sensor Integration

by adafruit_support_bill on Tue Jun 16, 2020 6:16 am

Thus I wonder, if my hypothesis is correct, what minimal hole diameter I should have for the leds ?

Sounds like it is more a question of how rigid the table is and how solidly are the transmitter and receiver ends of the sensor mounted.

Using the 3mm version of the sensor, I'd make your holes at least 3mm also. Mount the sensor components as close as possible to the holes and make sure that they are solidly mounted so that vibration does not cause the sensor to move relative to the hole.

The 5mm sensor will give you a bit more range. But like the 3mm sensor, you need to maintain good alignment of the whole system for reliable operation.

adafruit_support_bill
 
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Re: Break Beam Sensor Integration

by Agrod on Tue Jun 16, 2020 11:48 am

Thanks for the answer.

I had already 3mm holes but I guess this is a bit at the limit since the walls still touches the glass of the leds.
I'll try screwing the sensor directly on the goal walls, and will increase the hole size to 5 mm.

What is the misalignment angle that is tolerated between the emitter and receiver when being at 22cm distance and when supplied in 5V ?

Agrod
 
Posts: 2
Joined: Tue Jun 16, 2020 3:39 am

Re: Break Beam Sensor Integration

by adafruit_support_bill on Tue Jun 16, 2020 12:06 pm

The transmitting LED projects a cone of about 10 degrees. However, the light does fall off pretty fast as you go away from the center of that. The intensity at the edge of the cone would be half of what it is at the center - giving you about half the range.

The angle of the cone may be further restricted by the hole if the material is thick. Since you are pretty close to the maximum range, you probably need to be aligned to within a degree or two at most.

adafruit_support_bill
 
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Joined: Sat Feb 07, 2009 10:11 am

Please be positive and constructive with your questions and comments.