[Shop-talk] Toughest EE question ever asked here.

[Randall]

---- Matt Wehland <mjw at littlegrassy.com> wrote: 
> I've always said that the sensors should be a little below hip level so 
> you can just wave your butt at them, with the card in your wallet.

I know one reason that might not be a good idea.  A previous employer had them at butt level and used them to track when we were in the building (and what building).  I always kept my card in my hip pocket (although I pulled it out for use).  A large percentage of the time, the incoming reader would trigger on the card in my jeans as I walked out through the turnstile.  Then when the next person came in, the system would log that I had come back in, rather than the other person.

The system didn't allow more than one to go in or out on the same card, so when that person then tried to leave, the system wouldn't let them!  Lots of confusion, which I found thoroughly amusing.  I quickly learned to lean over the turnstile, wave my card at the reader on the other side, then turn it in (so the system thought I just came in), so then it would let me out.  The guards looked at me funny, but had no procedure that said I couldn't do that, so they never objected.

Of course, the problem would have been a lot more serious if there hadn't been a guard to override the system (or no way to lean over and trigger the other reader).

Just for grins, I tried my current card with it held tightly to my cell phone.  Still works solidly with the phone on the outside of the card, and even sometimes with the phone between the reader and card!

And they aren't just proximity detectors, because some doors around here won't open for me. (I'm not authorized to be on the roof, for example.)  So far, the only failures I've seen have been pretty obvious, like when one of the readers filled with rain water or several months after the card delaminated (from the constant flexing when I sit on it).

Randall