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29th November 2003 12:06 AM #1 
Digital Thermometer using op-amps, A/D converters & disp
Hi everybody! I'm on a new project...
Could anybody help me doing this circuit: I need to sense temperature and display it in 7-segments displays.
I suppose I have to use op-amp [what LM??], temperature sensor [someone told me to use LM335 and I read that AD590 could be usefull], an A/D converter, a decoder and of course two [?] 7-Segments displays.
I'm really really lost in this, i even don't know how to start. I have datasheets for all this things, but they don't seem to help me much :? ...
If somebody could show me a schematic diagram or something i would really appreciate it :wink:
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30th November 2003 02:08 AM #2
The AD590 puts out 1uA per degree Kelvin, so a negative bias of 2.73 volts is needed to have the A/D output read zero at zero degrees C. This is a start, check out the TC14433/A A/D converter. It has 3 1/2 digits output but you don't have to use all the digits. For another option, use an inexpensive voltmeter to read the voltage.
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3rd December 2003 10:02 PM #3
You could use the LM34 which measures 10mv/F. From that you send the analog output to an 8-bit A/D converter like the ADC0804. From there you need to output the digital output to a display. You could program an EPROM to convert the digital output to a BCD format and then feed those into a 7-segment display(using drivers of-course)
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