On Mon, Dec 07, 2015 at 10:41:15AM -0800, Bob Blick wrote:
> On Mon, Dec 7, 2015, at 10:35 AM, Byron Jeff wrote:
>=20
> > Bob,
> >=20
> > My thought process is trying to track down the chip is a fools errand
> > just
> > because there are so many chips that fit the description.
> >=20
> > Is it possible to do a black box approach? Essentially there are only 6
> > pins to decode. Figure out which are inputs and outputs. Then use a log=
ic
> > analyzer to grab the functional operation of the device.=20
> >=20
> > At that point figure out if a PIC can mimic that operation. If so, then
> > it
> > really doesn't matter what the original chip was since its functionalit=
y
> > was captured.
> >=20
> > I hope I didn't miss some obvious flaw to this approach.
> >=20
> > BAJ
>=20
> Hi Byron,
>=20
> I pretty much figured out what it's doing. One pin sends pulses to the
> LED, another monitors the phototransistor, another drives the motor. The
> discretes are for buffering and the phototransistor amp. I'm not sure
> what the comparator chip does, perhaps they don't trust the
> microcontroller's brownout detector.=20
>=20
> What really caught my interest is why there are no markings on the chip.
> It seems very strange. The operation is so simple there wouldn't be any
> reason to try to obscure the part number.

Chip marking costs money.  Especially if it is a custom or programmed
chip, or a chip that is commonly requested of the foundary by other
customers without markings.  Why would they waste money on marking?

The markings on the tape reel should be enough.

I'm interested in any photograph of the board.  The most likely
matching product that I've got are three liquid soap dispensers,
powered from either 4 AA or 3 AA (variation in purchase date).

Transmissive IR though, not reflective.  Runs what sounds like a
peristaltic pump.  Also has a red LED for battery low indicator.

Haven't had the joy of disassembly yet, saving it up for a rainy day.
But no rain for a while.

I mention the matching product because it seems likely that a similar
design may have been used for the non-liquid product you've described.
;-)

--=20
James Cameron
http://quozl.netrek.org/
--=20
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