Hi Michel,
you are right, I did not assume it was so complicated. However, have you
considered using frequency modulation of the IR signal? This way you
could easily subtract daylight digitally.
Jens
It really is a bit more complicated than that Jens. I generate a very
short but very strong IR pulse, I'd have to check the exact numbers
but it is somewhere around 250mA for 2 or 3 usec. The IR light
reflects from an object above the watch (a hand for example) onto an
IR photodiode. To make this work in all situations, the photodiode
should not saturate when there's a lot of light around (say you are
outside in the sunshine), so it's series resistor is relatively low
(which also helps making it very fast) and the signal received from
the powerful 250mA pulse is only like 40mV.
I first built that with some gates, capacitors and resistors. It
worked very well but used about 400uA average current if I am not
mistaken.
10uA is pretty much what it should be according to the data sheets if
you add up all the currents. Honestly, a battery will last for ages
(about 8 years) with a 10uA load, so I am really not worried about
that. It's just that the processor supports deep sleep mode, so I'd
like to incorporate that as well
Michel
On Apr 21, 7:59 pm, jb-electronics<[email protected]>
wrote:
Hello Michel,
Problem is that I need more components to be able to generate the
interrupt
I would have used simple diodes that are OR'ed together to the external
interrupt pin.
and believe it or not, it actually used more current.
Actually, I don't see that happening with diodes, do you? OK, if your
sources have different voltage levels you need shifters and these
require current, of course.
Standby mode means the processor is in sleep mode but wakes up about 8
times per second to check the sensor. The sensor only uses 2uA but the
processor uses more current in sleep than in deep sleep mode, so all
together it is 10uA.
Have you played around with the configuration bits? I once realised that
a silly enabled Brown-Out detect (which makes no sense with
battery-powered devices) takes up almost all the current.
Sorry if this has been mentioned before, but which processor do you use?
Best regards,
Jens
In deep sleep, the processor is completely powered down, only the RTCC
continues running. It can only be awakened by an external interrupt
(push button rather than motion sensor).
Michel
On Apr 21, 7:23 am, jb-electronics<[email protected]>
wrote:
Looks very good!
Total circuit power is about 10uA during standby mode and 2uA during
deep sleep.
Deep sleep will be entered after a standby time-out to save battery
life. Clock will still run in deep-sleep mode.
I am curious: Do you use an external interrupt to wake the processor in
case of a motion etc? This might be useful and could avoid the "standby
mode" altogether.
Jens
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