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ABSTRACT
The o bjective o f the project was to develop a t e mp e ra t ur e co n trol
syste m for maint ai ning a pre se t se qu e n ce of s pecified temperatures in
a liquid substance during the mixing p rocess in a boiler. The de po\:v er
s uppl y i s res ponsible · for po wering each pa rt of the sys t e m . T he
temperature of the liquid chemical i s sensed by a temperature-sen s itiYe
re s i s t o r called a therm is t o r. The t em p erat ur e of the c h emi cal m ixture
determine s the re s istance of the th ermist o r. The temperatur e- t o-vo lta g e
conversion ci r cui t produ ces an o utput vo lt age that i s prop ortion a l to
the temperatu re. The output goes t o an analog-to- di gital converter
(A D C) which co n vert s the vo lt age to di g ital form. The digital
processo r ad d s t h e appropriate scal in g and lineari zat i o n t o the
di giti z ed vo l ta ge and send s i t to the heater co ntrol circuit th a t is
programm ed t o sequence throu g h a ser i es of se t - point temperature s
durin g th e mixing process. The heater control ci r cu it co mpar es the se
t-p oin t t e mt-p era t ure to the actual temt-pera tu re as mea s ur ed b y the
t e mperature- t o-vo lta ge co nver si o n circuit and m a ke s t h e p roper
adjustment s of t he beatin g el eme n t. The details of th e de sig n
devel o ped were based on a Microch ip PI CI 6F84a, are d escri bed . The
pedag og i ca l va l ue of the probl em · i s also di s cussed t h rough a
d escript io n of some of th e k ey s t e p s in th e de s i g n process. lt i s s hown
t hat sol uti on r equ ir ed bro ad knowledge dr aw n from s ever a l engi n eering
d iscip line s including el t: c tr ical. mechanical and con t r o l S ' s t ems
e n grneen n g.
