The temperature control circuit is a circuit thermal simple but very precise control that can be used in applications where automatic temperature control. The circuit switches a miniature relay on or off depending on the temperature detected by the sensor chip LM35DZ single temperature.
When LM35DZ detects a temperature higher than the preset level (set by VR1), the relay is activated. When the temperature drops below the set temperature, the relay is deactivated. The circuit can work with any 12V DC source or battery (100 mA min.)
When LM35DZ detects a temperature higher than the preset level (set by VR1), the relay is activated. When the temperature drops below the set temperature, the relay is deactivated. The circuit can work with any 12V DC source or battery (100 mA min.)
Part list:
IC1 : LM35DZ
IC2 : TL431
IC3 : LM358
LED1 – 3mm or 5mm LED
Q1 – General purpose PNP transistor ( A1015,…) with E-C-B pin-out)
D1, D2 — 1N4148
D3, D4 — 1N400x (x=2,,,,.7)
ZD1 — Zener diode, 13V, 400mW
Preset (trim pot) : 2.2K (Temperature set point)
R1 – 10K
R2 – 4.7M
R3 – 1.2K
R4 – 1K
R5 – 1K
R6 – 33Ω
C1 – 0.1 µF ceramic or mylar cap
C2 – 470 µF or 680 µF electrolytic cap. (16V min)
Miniature relay – DC12V DPDT, Coil = 400 Ω or higher
