Re: Anything like a No-Slot Clock for a II+?

[mjmahon@aol.com (Michael J. Mahon)]

Scott Alfter wrote:

>I'm thinking of taking a II+ that's currently gathering dust and putting it
>to work controlling my beer fridge.  I'm a homebrewer, and it'd be nice to
>have something that could slowly ramp temperatures up and down for the
>diacetyl rest, lagering, etc.  I figure a 64K II+ with a floppy drive would
>be perfect for the job...it'll still run ProDOS, so I can have it log
>temperatures to a floppy, read that disk into my IIGS, and export the data
>elsewhere from there.  I'm even repainting the fridge in beige (the original
>white paint was looking nasty), so an older Apple II will kinda-sorta match
>it in color. :-)
>
>I figure that the joystick connector has the necessary I/O...a thermistor on
>a joystick input and a relay on an annunciator output (along with whatever
>buffering electronics might be needed) would do the job.  Since I'll want to
>change temperatures slowly (maybe 1�F/hr) and I'll want to periodically log
>the temperature (maybe once per minute), a real-time clock of some sort will
>be necessary.

A thermistor will work fine.  You may have to fiddle a bit or use signal
conditioning to get 1 degree resolution over your desired temperature
range with the Apple paddle circuitry.

>I could wait for a clock card to show up on eBay or in
>comp.sys.apple2.marketplace, but that'd be too easy.  I know the No-Slot
>Clock was a variant of the Dallas SmartWatch that would work in a ROM socket
>in a IIe or IIc (which use 8K ROMs), but is there a version that would work
>in the 2K ROM sockets of a II+?  If there isn't, would it be feasible to
>build an "interposer" that would enable the clock to work in a 2K socket? 
>If I could put it in the right socket for the No-Slot Clock driver to see it
>and make it available to ProDOS, that would be an added bonus...but it would
>be enough if I could just access it through my software.

It will take an adapter, as you describe.  An alternative is to put it under
any standard (27xx) slot ROM, if you have any such card(s) in the computer.
(For example, a 3.5" disk controller...)

>While I'm at it, what would be recommended as a buffer circuit between an
>annunciator output and a relay with a 12VDC coil?  The relay would be used
>to switch the compressor on and off...since the contacts will carry 120VAC
>and moderate current, I'm guessing that something with a 12VDC coil would be
>needed.  I can tap power from the power supply wiring easily enough, but
>what would be needed to switch the relay without toasting the computer's
>annunciator output?

I'd actually recommend using a small 5v or 12v relay to control a
larger-contact
12v relay.  Motors have fierce starting currents, and compressor motors can
even stall on start (if short-cycled).  The coil current of a larger 12v relay
can
be hundreds of milliamps, so it's worth choosing one with a reasonable
coil resistance, to minimize arcing on the small relay contacts and to
reduce 12v supply loading on the Apple.

The small relay can be easily driven by a 2N2222, for example, switched by
the annunciator output.
-michael

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