Max. and Min. Thermometer

Photograph of the prototype hardware:

Note: the LM35 temperature sensor is at the end of the flexible lead shown at the bottom of the picture.

Circuit diagram:

Controlling program:

(*$d 2313 - processor is AT90S2313*)

(*$c 4 - 4MHz clock crystal *)

PROGRAM Thermometer;

(* Simple thermometer program to check operation of LCD and ADC0831A modules *)

USES

LCDdisp2, Convert, ADC0831A; (* declare these library modules *)

VAR

max, min, ambient : BYTE;

(* declare subroutines from LCDdisp2 module *)

PROCEDURE InitLCD; LIBRARY;

PROCEDURE WriteCh(ch:BYTE); LIBRARY;

PROCEDURE WriteStr(str:STRING); LIBRARY;

PROCEDURE CursorAt(posn:BYTE); LIBRARY;

PROCEDURE ClearLCD; LIBRARY;

(* declare subroutines from convert module *)

PROCEDURE Bin2BCD(VAR hundreds,tens,units:BYTE; data:BYTE); LIBRARY;

FUNCTION Bin2String(data:BYTE):STRING; LIBRARY;

(* declare subroutines from ADC0831A module *)

PROCEDURE InitADC; LIBRARY;

FUNCTION GetADC:BYTE; LIBRARY;

BEGIN

(* setup LCD *)

InitLCD;

InitADC;

ClearLCD;

(* display constant text *)

CursorAt(#1);

WriteStr("Ambient="); (* msg on top line *)

CursorAt(#11);

WriteCh(Chr($b2)); WriteCh('C'); (* °C *)

CursorAt(#16);

WriteStr("Max= "); WriteCh(Chr($b2));

WriteStr("C Min=");

CursorAt(#31);

WriteCh(Chr($b2));

(* set initial temps *)

ambient := GetADC;

max := ambient; min := ambient;

(* main loop *)

REPEAT

(* display temperatures *)

CursorAt(#9);

WriteStr(Bin2String(ambient));

CursorAt(#20);

WriteStr(Bin2String(max));

CursorAt(#29);

WriteStr(Bin2String(min));

Wait(500);

(* sample temperature again *)

ambient := GetADC;

(* update max/min temps if necessary *)

IF ambient > max THEN

max := ambient

ELSE IF ambient < min THEN

min := ambient;

FOREVER;

END.

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