A card can’t get sideways due the way the machine is designed. I supposed if my fan was more powerful I could have problems with that at the top, but I think pulsing the fan would get stuck cards unstuck. I could also alter the geometry of the clear box on top top to minimize this problem if needed.

Regarding recognition of orientation, use cards with a blue back and illuminate it with a blue led. The back should look blank or nearly so to the detector while the front will have dark spots.

Regarding the airflow, I am assuming the ‘vent’ is the piece of wood with all the holes in it. Try making the holes bigger or closer together and only the bottom half or two thirds of the ramp. Put a row of holes on each side just above the vent plate so that any cards that fall down along the walls will get the bottom edge pushed back into the flow stream. Also, if you hook up the fan to suck air out of the top you won’t need to run pipes to the side jets and if painting the slides doesn’t help you could turn them into little air hockey tables.

BTW What happens when the cards get turned crossways?

Gordie

I didn’t expect many people to read this post since it didn’t work so I didn’t do a very thorough writeup. Let me list the problems I saw and make some comments.

1) I claimed that the fan was underpowered. This isn’t entirely true. If the fan moved 500 cubic feet of air a minute as advertised I’d have over 30 mph wind and that would be more than enough to blow the cards around. The problem is that airflow is restricted at certain points. One of those is the is the vent. I did try taping up some of the holes and it did not help. I actually found that removing the vent entirely gave the best performance, but it was still not good enough. I think an aerospace engineer could calculate why the observed airflow is so much less the theoretical max, but I can’t. All I know is I was hoping for 10%-20% drop and I’m probably seeing 70-80%. As it stands the cards get blown around as long as they are perpendicular to the airflow they get blown around, but if they turn sideways they fall and get stuck at the bottom. One person on my website suggested using compressed air and I like that idea, but it would increase the cost. I also think replacing the fan entirely with a spinning plexiglass cube might be a good solution.

2) I completely agree with those above that a webcam could easily detect if a card is upside down. However, I was planning to go a cheaper route. I was planning to use just an Arduino and no PC. I know if I put a black dot on one side of the cards I could reliably detect that dot with IR sensor. I think I could have also probably used a specialized clear IR paint. Another option would be to find a deck of cards that allowed the IR sensor to work without modifying the cards. I am pretty sure this problem is easy to solve so I was saving it to last.

3) Cards sometimes randomly got stuck in the slide system. There is a chance that adding paint and sanding would make the slides slippery enough so this didn’t happen, but I suspect I would have needed to do some minor tweaks to the slide system. By tweaks I mean change slide positions and angles.

4) I hadn’t hooked up the servos so I don’t know if there would have been a problem with selecting a single card. My hunch is that there would be a problem here and I’m not sure of an easy way to solve this one. My best bet would be buying those slightly thicker plastic cards.