long distance IR
DESURMONT,BENJAMIN LOUIS J,MR
HP48g, you can communicate from 10 meters ? And, Is it easy to make an
FM radio i/o which, you can communicate from 1 Km (and do a HP48 radio
network) ? am i dreaming ?
from DXA
WayneAtDSN
About withdrawing a resistor: I've opened up the case, and as far as I can
see, the two IR leds feed directly into one of three IC's. To me: There is
no IR cripple.
As for the FM radio thing: I won't know until I get into Ham.
Hope this helps.
--Wayne Lee
Matthew Carlson
: Message-ID: <19JUN95.25...@VM1.MCGILL.CA>
: --Wayne Lee
Trust me there is a shunt resistor to limit the current in the reciever.
Where it is or how it is implamented is another thing. They could have
used an op-amp in one of the ic's for it. Or they could have just used a
real resistor in the ic. It could be a transistor circuit. Anything that
limits the current. If you give me the part numbers of those ic's, a
diagram of how they are connected to the reciever and any resistors or
caps they connect to. I may be able to help.
--
Matthew Carlson <car...@rahul.net>
Dave Arnett
>WayneAtDSN (wayne...@aol.com) wrote:
<snip>
>: About withdrawing a resistor: I've opened up the case, and as far as I can
>: see, the two IR leds feed directly into one of three IC's. To me: There is
>: no IR cripple.
>Trust me there is a shunt resistor to limit the current in the reciever.
>Where it is or how it is implamented is another thing. They could have
>used an op-amp in one of the ic's for it. Or they could have just used a
>real resistor in the ic. It could be a transistor circuit. Anything that
>limits the current. If you give me the part numbers of those ic's, a
>diagram of how they are connected to the reciever and any resistors or
>caps they connect to. I may be able to help.
Never say we keep technical info from the intelligent public....
Vco--------------
| |
| |
R R
R 1M R 18k
R R
| |
| C
| Q
|---------BQ |------------Pin 160
| Q PNP IR Sens | "IRI"
| E C Yorke CPU chip
| | Q 00048-80048
| |------RRR---------------BQ (Different part
| | 220k | Q on S-series,
| R R E NPN same function.)
| R 220k R 560k |
| R R |
C | | |
Q | | |
QB---------| | |
Q | | |
E NPN C | |
| === 0.022 uF | |
| C | |
| | | |
| | | |
GND-----------------------------------------|
For Info, Vco is the 5V power supply which is NOT energized during
the sleep modes. And Yes, the IR is sensed through a photosensitive
PNP transistor. I hope this diagram has no typographical errors.
Use it at your own risk and discretion. THis describes the G and S
series HP48 calculators, as designed and shipped from the factory.
Dave.
------
I don't speak for HP when I post here, and I do not recommend opening
HP48 calculators. I also maintain that "crippled" is an incorrect
word for describing the HP48 IR detector circuit.