Jason S wrote:
"James Sweet" wrote in message
news:1ZOjf.1374$fY3.718@trnddc01...

Jason S wrote:

Hi,

I'm looking for a circuit that will represent temperature ranges up to 60
degrees (celcius) using at least 3 LED's or transistors as the outputs
for
each range, but I DO NOT want a digital display like a 7-segment or LCD
though.
I want to be able to utilize these outputs to control others parts of my
circuitry (perhaps like voltage calibration).

Example:
LED 1 (green) = -10-20 degrees,
LED 2 (yellow) = 20-30 degrees,
LED 3 (red) = 40+ degrees,

I am open to all suggestions.
Thanks in advance.

J




How about an analog bargraph IC? Otherwise a quad comparator chip could be
setup to do this, IIRC the LM329 is such a chip.



Hi thanks for the reply.
The quad comparator wouldn't really work, because only 1 'output'
LED/Transistor needs to be lit at any given time, not more than 1. The
analog bargraph would probably work, but would need to be able to set it up
as 'Dot' mode (probably easy to do), then I could use logic gates to provide
filtering from each of the outputs to produce my final 3 or 4 output ranges.
However, any ideas on how to hook up a temperature sensor to it? I found
schematics based on voltage measurement, not I know nothing about temp
sensors and how I would hook it up with this type of circuit. Can you point
me in the right direction?

Thanks, J



Use a darlington transistor, for silicon the leak current doubles
every 6 degrees celcius,and the leak current of the first
transistor multiplied twice by your current gain should be
around the Milliamp range.Up to about 100 degrees,works nicely.
Add 3 comparators to check for voltage level across a suitable
resistor,you could use a quad IC 741 type for that.