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Re: Anything like a No-Slot Clock for a II+?
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The new paint is drying on the fridge...finally got around to digging
through the catalogs to see what the new electronics will cost.
In article <20030120190031.19058.00000240@mb-fp.aol.com>,
Michael J. Mahon <mjmahon@aol.com> wrote:
>Scott Alfter replied:
>>In article <20030120054747.14490.00000200@mb-fc.aol.com>,
>>Michael J. Mahon <mjmahon@aol.com> wrote:
>>>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 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 can write a routine that'll read a paddle input with greater resolution
>>than the one that's in ROM. If that's not sufficient, it shouldn't be much
>>to lash up a circuit around a 555 that would do the job...if that ends up
>>being necessary, a button input would be used instead of a paddle input.
>
>That should do it. Just be sure that the thermistor you choose can
>easily provide the needed resolution near room temperature, since
>thermistor response is nonlinear.
Since I was already thinking of putting in a SmartWatch (more on that
later), I figured I'd see what else is available from Dallas. It turns out
that there's a temperature sensor (the DS18B20) available. It uses their
one-wire interface (should be able to lash something compatible together
that'll work through the game port) and offers 0.5�C accuracy from -10�C to
+85�C...more than a wide-enough range for the beer fridge. It's available
in a TO-92 package, so all it'd need is a three-wire cable to carry power
and signal to it.
>>>>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?
>>>
>>>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...)
The DS1216E would be the most likely candidate...but DigiKey wants over
$38.00 for one of these. I might spring for one of these for my IIe, but
it's a bit more than I want to put into this project.
As it turns out, though, there are other timekeeper chips available. The
DS2417 uses the same interface as the aforementioned temperature sensor.
It's basically a 32-bit counter that gets bumped once every second. I'd
have to write a driver for it if I want ProDOS 8 to recognize it, but it
costs less than $3. A crystal, backup battery, and diode should be all it'd
take to make a RTC out of it that would keep running while the computer is
shut off.
>>I already have a relay with contacts rated for either 5A or 10A...don't
>>remember which offhand, but 10A seems more likely.
>
>The starting current could easily exceed 10A, but since it has held
>up OK controlling this motor, it should be fine.
>
>The critical question, then, is what is its coil current? You may
>be able to get by with a 2N2222 driven hard, but you may need
>a Darlington pair.
It's Radio Shack #275-218:
http://support.radioshack.com/support_supplies/doc9/9525.htm
Coil current is 75 mA. Here's a 2N2222 datasheet I found after a quick
google:
http://www.semiconductors.philips.com/acrobat/datasheets/2N2222_CNV_2.pdf
Looks like a 2N2222 should easily be up to the task. Even if the coil
current at turn-on is 10x nominal, that would still be within the limit, and
it would quickly settle down to less than that.
_/_ Scott Alfter
/ v \ salfter@salfter.dyndns.org
(IIGS( http://salfter.dyndns.org Top-posting!
\_^_/ pkill -9 /bin/laden >What is the most annoying thing on Usenet?
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