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This PIC based LCD Temperature measurement project
was planned to measure two Temperatures Simultaneously. It can be
effectively used to measure your room temperature and may be used for
measuring RF Amplifier Temp. I made
this project for a friend who wanted to measure inside & outside
temp in a Vegetable cold storage. It worked very accurately and
reliably for last few months.
In addition to LCD display, TH1 also produces
DATA Logger output available at D9F connector which may be used for
such purposes.
The Hardware is quite simple using a PIC16F876A
& its two 10bit A/D measuring inputs. Temperature sensors are tiny
3 terminal MCP1047A.
Accurate reference is created for PIC by using
MCP1541 which is a 4.096. Its buffered by a Rail to Rail Op.Amp
MCP6022. A voltage divided is used to get 2.56V for sensors resulting
in a simple calculation of T = Reading - 200/4
Data-Logger output is available at Pin RC6, in a
serial output – the TH1 will send the temperature readings every
second using 9600/N/8/1 format. Please note that Output from TH1 is at
TTL level.
A MAX232 level converter
is necessary in order to feed this info to a RS232 port and any
terminal program such as HyperTerminal is suitable for this
purpose. Project details of making an RS232
level converter is available on this site.
Two sensors are used. Sensors are encapsulated
inside a 3.5mm phono jack and they were comfortable inside it! I
wanted to place one sensor inside the project board but a fear of heat
generated within the board (Especially from 7805 with backlight
"on") made me move both sensors out-board for peace of
mind!!
Sensors require a simple two core (2 wires in
center and a shielding braid) shielded cable used for microphone/audio
purposes.
Results of this LCD meter were very encouraging
and I am sure many radio amateurs would like to place this meter in
their project or in their ham shack to measure various temperature
levels. (Not to forget the Kitchen!!)
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