On 2/6/2012 6:31 PM, Rich Webb wrote:
On Mon, 6 Feb 2012 22:29:52 -0000, "Gareth Magennis"
wrote:
"Rich wrote in message
...
On Mon, 06 Feb 2012 13:10:10 -0800, wrote:
I recently bought a heating pad which has a "feature" which shuts the
heat off after 2 hours. Virtually all pads seem to be made this way now,
unfortunately. I would like to defeat this. I can probably jumper
around the timer control portion of the switch to accomplish this, but I
see in doing some searching that on at least one older model, some
modification of the circuitry around the chip can accomplish this, too
http://www.ralree.com/2007/12/13/dis...e-heating-pad/
Unfortunately, the circuit on that pad is not the same as mine, which
is centered around an 8 pin chip marked "SEDS 13-000022 R1017A" I can't
seem to find any data on this chip. Tried www.alldatasheet.com, no info
that I could find. Anyone know where I might look, or have any other
ideas for eliminating the timed off action?
A 555 timer chip is only eight pins but so are many smaller
microcontrollers. Can you take a picture of the circuit board (both
sides, perhaps) and upload that to Flickr, ImageShack, or similar? That
might help narrow down the choices somewhat.
--
Rich Webb Norfolk, VA
I suspect this is probably a Chinese in-house number. The chip could be
anything and there is unlikely to be any data out there on it.
True but it's most likely going to be a counter like the other examples
or, perhaps, something more modern like the aforementioned uC with an
internal RC oscillator. Could be a 4-banger, even. But looking at where
it is in the layout can give some clues to getting the OP a way to
accomplish his intent.
Thanks for the great replies. I'm not sure what the chip is, it's a
SOP8 package, not a DIP like a 555 timer. Probably right, some
proprietary design with little data available. One side of the line is
switched via a small transistor, I disconnected the transistor & ran
that side of the line directly. Heat levels are adjusted with the
control switch on the other side of the line. So far so good. Also,
the bloody thing is SUPPOSED to shut off at 2 hours, and it's barely
making it past ONE. PITA.
Dan