Differential thermostate for solar pump

This concept only differential temperature controller is capable of reading several DS1820 sensors.

Schematics

Click on image

Also available as PDF

BOM

refdes	device	               value	        quantity
C1	POLARIZED_CAPACITOR	10uF		1
C2	CAPACITOR	        22p		1
C3	CAPACITOR	        22p		1
C4	POLARIZED_CAPACITOR	2200uF/16V	1
C5	POLARIZED_CAPACITOR	220uF/16V	1
C6	CAPACITOR	        100n		1
C7	CAPACITOR	        100n		1
D3	DIODE	                1N4001		1
D4	DIODE	                1N4001		1
F1	FUSE	                T20mA		1
L1	COIL	                Relay 12V SPST	1
LED1	LED			RED 3mm         1
PUMP1	Solar PUMP		UPS25/40       	1
Q1	Transistor              BS170		1
R3	RESISTOR	        10k		1
R4	NTC	                4.7ohm		1
R6	RESISTOR	        1k8		1
Rpu	RESISTOR	        3k9		1
S1	SWITCH_PUSHBUTTON_NC			1
S2	SWITCH_PUSHBUTTON_NC			1
S4	SWITCH_PUSHBUTTON_NC			1
T1	TRANSFORMER	        Trafo 5VA 2x9V 	1
U1	AT89C2051		DIP20+socket    1
U4	78L05			                1
V?	MOV	Varistor 250VK5	MOV	        1
X1	CRYSTAL	10.092MHz                       1
LCD1    LCD2x16		                        1
Q2,Q3,Q4 DS1820 digital thermometer             3