Friday, September 14, 2007

[oopic] Oopic and the LM335 Temperature Sensor

Guys,

I am having a bit of trouble interfacing an LM335 to the Ooopic ADC
lines and wondered if someone has already been here and got a circuit
which works.

I cant seem to get a reliable reading or a precise enough measurement.
Even if I try to use the extvref line with a voltage as low as 4 volts
(which deosnt seem to make a difference) - I just cant seem to get a
correct reading. It deosnt help that the oopic cant do floating point
math.

Deos anyone have a suitable circuit that would allow me to read up to
5 lm335 temp chips but with some sort of op amp subtractor, say, to
remove 2 volts so I can more or less read the true temperature
directly, or at least make a eeprom lookup table to get the correct
values?

Any help, thought appreciated.

I have tried both firmware Version 1 and 2.2+ on Oopic 2's.

Cheers,
dicky


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