Temperature Control
Circuit :
Image
Courtesy Texas Instrument
The temperature
controller circuit using +5 V voltage source from I/O slot at IBM
PC/XT/AT.
IC LM 335 from Texas
Instrument have the ability to detect temperature from ranging -40
celcius degree until 100 celcius degree.
This LM 335 from
Texas Instrument , is zener diode which have the linear coefficient
voltage increment related with increment of temperature with formula
:
Vz = + 10 mV/
C (celcius degree) , with
current opeartion between 400 uA until 5 mA.
On
the circuit Resistor 2.2 K use for limit the current flow to cathode
pin from LM 335 which is output of LM 335 sensor temperature.
On
circuit Resistance of R is 2.2 K , and at 25 Celcius degree from data
sheet of LM 335 , voltage at LM 335 will be 2.982 Volt , so current
flow can be calculate :
Vcc
= + 5 V
Voltage
at 25 Celcius on LM 335 = 2.982 V
Voltage
at Resistor R 2.2K is = 2.018 V
Current
flow through LM 335 and R will be = 2.018 V / 2.2 K = 0.9 mA
This
0.9 mA current at LM 335 still on at range of sensor LM 335, and then
the output cathode pin of LM 335 sensor from Texas Instrument connect
to input 0 of ADC0809 Analog and Digital convertion data from Texas
Instrument at pin 26.
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