LM35 to ADC
Published in issue 356, July 2006
The circuit described here is the digital and display section of a thermometer; the analogue circuitry and signal conditioning required to use an LM35 temperature sensor are described elsewhere in this issue (‘LM35 to ADC’). The analogue-to-digital converter used here is hidden inside a PIC16F873 microcontroller behind the RA5 port pin. It has a resolution of 10 bits (1024 steps), allowing a temperature range of 128 ?C to be divided into steps of exactly 128 ?C / 1024 = 0.125 ?C.
R1 = 10k
R2-R13 = 220
C1 = 100nF
C2 = 10µF 16V radial
D1-D5,D7-D11 = LED, 5mm
D6 = TwinLED (DuoLED) green/yellow
IC1 = PIC16F873-20/SP, programmed, order code 030190-41
X1 = 8MHz ceramic resonator (3 pins)
S1,S2 = BCD complement switch (APEM PT65-702)
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Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.