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Author Topic: What sensor should I use to detect object going through a hole?  (Read 2303 times)
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texas
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I may have been wrong with the sizes. The hole diameter may be 4". I'll have to confirm this.

RFID is a very interesting option. It would allow me to identify which player's washer went through, which would be great. But I would need to rule out washers sitting on top of the board (that did not go in the hole). And I would worry about the constant throwing and hitting of the board wrecking the RFID chip.

I was just kidding about the RFID, but it seems to have the unique advantage that you could let several people throw at the same time and still keep track of it all.  I have no idea how durable the tags are, but generally speaking if there is a demand, then there is a part that will work.  You might want to switch away from metal washers to something a little less troublesome to RF, like plastic or rubber with the tag embedded inside.

@crossroads:  I would only use the reflection sensors along with the direct beam sensors, sort of a backup way to catch anything trying to slip through the beams.  All in all, a laser diode is probably the best bang for the buck solution so far and a little bit of water vapor or smoke combined with a visible red or green diode wouldn't hurt the wow factor any. 
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Thanks to everyone for their input. It's most appreciated. It's been made clear to me that I can't change the physical characteristics of the game itself, so changing the washer type or size, etc., isn't an option.

Another benefit of using an IR sensor is that I wouldn't have to worry about changing light conditions, correct? And do I need to do anything special to make an IR sensor work with a red LED?

Thanks again!
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You go and buy a special IR Led,   they are about 20 cents each
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Another benefit of using an IR sensor is that I wouldn't have to worry about changing light conditions, correct? And do I need to do anything special to make an IR sensor work with a red LED?

IR phototransistors/diodes are still plenty sensitive to daylight. They have a pretty wide sensitivity.
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Another benefit of using an IR sensor is that I wouldn't have to worry about changing light conditions, correct? And do I need to do anything special to make an IR sensor work with a red LED?

IR phototransistors/diodes are still plenty sensitive to daylight. They have a pretty wide sensitivity.

This is why I suggest using a modulated IR source and a dedicated IR sensor such as those used in remote controls.  They have nice signal processing circuitry built in that's pretty hard to duplicate on your own using just a phototransistor.
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