propstick power pins ?

Don Pomplun

I just assembled my propstick, and, before "permanently" installing it in a protoboard, I was wondering if there was a good reason why the 2 power pins weren't also set up as wirewrap pins. That way the protoboard could more easily supply prop power without the danger of a (high voltage) 5 volt lead popping out of those supplied pins and hitting some 3 volt spot.
-- Don

Phil Pilgrim (PhiPi)

Don,

The reason is parallax. No, not the good kind that resides in Rocklin, but optical parallax. Because the chip label sits so high above the breadboard, it would be much too easy to confuse A16 with Vin if Vin were just another pin. I decided from the get-go that it was best to make Vin easily distinguishable from pins that wouldn't tolerate a high voltage.

-Phil

Don Pomplun

I guess your oint is that if they were just 2 more look-alike pins, you might mis-mount the prop chip and end up applying 5v to A15 & A16. Good point, except that I see no reason to ever remove & reinsert the chip. And as I look at the supplied 5v connectors, they seem *dangerously* close to those 2 I/O pins to be sticking wires in them. I think it's safest to feed power from the bottom by converting to a coule wirewrap pins for power.
-- Don

Phil Pilgrim (PhiPi)

Don,

I was actually more concerned about someone inserting a +5V (or more) lead into the breadboard at A16. Also, you just can't buy 21-pin socket strips off the shelf. That last pin position would have to be unique, no matter what. But, in any event, there's nothing that says you can't replace the little sockets with a couple wirewrap pins, if that's what you prefer!

-Phil

Don Pomplun

There's always the danger of sticking a HV lead into any breadboard hole, I suppose.
Maybe not 21 pin sockets, but I have a bunch of 24" long strips that you can break off at any number of pins (they're not wirewrap, but I imagine those would also be available).

Another question, now that we've beat this horse into submission - - - For 5v chips (like a PIC), one could feed 12v RS232 in using a 22K series resistor (because the input pin is not really infinite resistance). Isn't it reasonable to assume that you could do something saimilar with the 3v P-chip?

Now that I'm nearing the end of chap 4, I'll be heading into the examples. I'm intrigued that you can, somehow do A/D & D/A. I'm hopeful that I can implement a touchtone decoder in software.

-- Don

Phil Pilgrim (PhiPi)

Don,

The high-voltage input question has been dealt with pretty thoroughly here: http://forums.parallax.com/showthread.php?p=585920. It's a good, valid question that seems to get asked anew every time the thread falls off the front page. Someone who can should probably make it a sticky thread. I hope the new manual gives it an exhaustive treatment.

-Phil

Chris Savage

Phil,

·· You have a good/valid point, and so the thread is sticky now.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Phil Pilgrim (PhiPi)

Thanks, Chris!