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update on DS1620 project

D

Dan

Jan 1, 1970
0
Last weekend I posted for help on running several DS1620's from a controller
card. I had problems getting more than 2 to work. Each run was less than 30'
using ethernet wire going to supply air, return air, outside under eve and
in the attic. I tried putting a decoupling cap on each remote board which
held the chip, then I tried doubling up the gnd and vcc with the extra
wires, then I tried bringing out more signals from the board - clk2 and rst2
in addition to clk1 and rst1. Now it works after modifying the software.
Only thing I can figure is there's too much of a voltage drop when all chip
are init'd and or queried at the same time. So as long as I don't access
more than 2 at a time it works.

Dan
 
M

Michael

Jan 1, 1970
0
Dan said:
Last weekend I posted for help on running several DS1620's from a controller
card. I had problems getting more than 2 to work. Each run was less than 30'
using ethernet wire going to supply air, return air, outside under eve and
in the attic. I tried putting a decoupling cap on each remote board which
held the chip, then I tried doubling up the gnd and vcc with the extra
wires, then I tried bringing out more signals from the board - clk2 and rst2
in addition to clk1 and rst1. Now it works after modifying the software.
Only thing I can figure is there's too much of a voltage drop when all chip
are init'd and or queried at the same time. So as long as I don't access
more than 2 at a time it works.

Dan


I have never used the DS1620 - use DS1820 exclusively - but probably
they're alike in the respect of pulling significantly more current after
a CONVERT-T command and until conversion is complete than when
quiescent. I know I went the 3- instead of 2-wire route because of the
extra hardware a "hard" pullup for the 2-wire config. would have
entailed.

By the way, one of my DS1820 devices reports that the outdoor temp. is
41.2F at the moment.
 
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