Re: Power cycling Mark IV

[hjohnson@pluto.njcc.com (Herbert R Johnson)]

On Wed, 27 Sep 2000 08:47:47 -0700, Chris Albertson <chris@216-178-250-236.lax1.phoenixdsl.net> wrote:
*>Ron, Arne,
*>
*>If what you really want is the ability to power cycle the
*>camera then why not simply power cycle the camera?  You
*>must in addition to the serial and parallel data cables 
*>also have a power cable running outside  You could switch
*>the power from indoors either manually or under control of
*>the PC.
*>
*>Ron Wickersham wrote:
*>> 
*>> Regarding reset:
*>> 
*>> rather than an extra line, i could supply a module that would look for
*>> "break" on the serial line to reset the Stamp.  the advantage being that
*>> if one wants to use fiber or other isolation technique then only the
*>> Tx and Rx lines need to be connected.
*>> 
*>> is the host PC going to be moved out on the pier when everything
*>> is debugged as was discussed before and then just run an isolated or
*>> fiber ethernet for communications to improve survival from lightning?
*>> 
*>> -ron
*>> 
*>> On Tue, 26 Sep 2000 aah@nofs.navy.mil wrote:
*>> 
*>> >  17) If the Stamp has a reset line, you might bring it back to the
*>> >      host computer so that you can reset the Stamp without having
*>> >      to run outside and cycle the power.  ----n you can cheat and
*>> >      use one of the serial cable handshake lines for this feature.

There seem to be two issues, one of a reset for the Stamp, and one for
power cycling either the camera or the Stamp. Then there is the business
of a long control/data cable between the camera and the controlling computer,
which is the current configuration. As for a "fiber ethernet", it simply
does not exist yet for the Mark IV.

Frankly, I'm always spooked when I see this "long cable" business, seems
like a long cable is an antenna looking for noise, or a wire looking for
lightning-induced surges or worse. More than one of the Mark III's has
suffered from some kind of power damage, ask the sites.

So the idea of a wire that would in effect LOOK for a big spike to reset
either the Stamp or the whole camera strikes me as a bad idea. It would
be a shame to mess up a camera run with a "reset" caused by a power surge.

If you must have some kind of remote power cycle, try to come up with
something which
is either wireless or has some kind of protection from noise and surges.
For instance, a really DUMB "power cycle" is to put an AC timer on the
camera which briefly turns off AC at, say, 9AM when the camera is neither
in use nor under development. I could imagine an X10 module to do the
same thing, except the camera's AC supply may not be on the same AC circuit
as the X10 controller - X10 control codes are transmitted by the
AC lines. Or, I suspect most large hardware stores carry an "ac remote" to turn
on a lamp with some kind of hand-operated RF controller. None of these require
any software, just a shopping trip and human intervention at the computer.

If a reset is to be sent over this 90-foot cable, some circuits
should be added to make sure the command must be a long pulse rather than
just any old "spike".

Herb Johnson

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