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

["Stephen Shaw" <bottrawler@junkbuster.zzn.com>]

On Sun, 26 Jan 2003 02:22:51 +0000, Scott Alfter wrote:

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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.

Try going to the Maxim Dallas website and ask for samples - I got two of
those that way - for free.


> 
> 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!
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>  Usenet?
> 
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