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Topic: Detecting each of up to 16 different things (Read 2 times) previous topic - next topic

GoForSmoke

I don't know these guys but it looks like a ready hardware part of the solution:
http://www.phidgets.com/products.php?product_id=1102_0

OTOH, knowing that black and white reflect differently you can try making your own sensor and yes, tape a bar code under each car.

Consider using white stripes (more reflective) for data and black stripes as reference widths. A zero would be a narrow white stripe and a one would be 3x as wide a white strip. The black stripes would all be narrow. You would be reading perhaps 10,000x a second, keep count of how many reads the last black stripe was and if the next white strip is less than 1.5x as many then it's a zero bit but if 2.5x or more then it's a one bit.
Then start your data sector with an attention section of 8 narrow b/w stripes followed by a wide black stripe, the next white stripe begins your data.

The boffo setup would read the same no matter which direction the train is going, attention section at both ends and each car's ID being symmetric. You could get away with 2 number / 4 white stripe codes that would read 0000 0000, 0001 1000, 0010 0100, etc.

I did kind of adapt an idea from Mitsubishi Labs there, but it's kind of adapted from old telegraph Morse code methods that had to be invented because humans don't tap keys with clock-like precision (long story short) so I doubt there will be a patent battle if you go to market.
Besides, I added the bit about using the black stripes for reference, Mitsubishi just used relative numbers of flash reads of data alone to know dit from dah.

The at least twice borrowed idea being that no data is not a data zero. That was used before computers, even the 1880's electro-mechanical type (hole or not being the data). IIRC the words are 'prior art'.  8)

Cool?
I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

Henry_Best


RFID tag on each train and a reader at the track?


An idea that I might consider. Where does one get RFID tags from and can they be programmed?

Henry_Best



Ir LED on each blinking at different rates.


That would mean having a power source (battery) on each truck. Trying to take power from the rails for these would be a no-no as the power is PWM and the wagons are too light to make constant contact with the rails.

Henry_Best



Assuming you've rigged up your IR reflectance sensor right (and that's a big assumption), it should trigger low when the white label of the barcode starts as hopefully the barcodes are the only reflective thing passing over the sensor.


I've not rigged anything yet, just trying to sort out the feasability :smiley-red:
Hopefully, the barcodes will be the most reflective thing passing over it. I could paint the remainder of the underside of the wagons matt black.
Thanks for your reply. I'll certainly consider it.


Henry_Best



A little mirror with bits of evenly spaced black tape. 


Thanks for your suggestion, but have you ever tried sticking 16 strips of tape, evenly spaced, to a little mirror?
A laser printer will give me quite reflective white and black evenly spaced lines.
But that's not the problem. The problem is: when do you start counting?

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