7. Electric expansion valve control circuit
B − 1 2 V
R 4 1 8
1
6
C N 1 5
1
5
6
1
4
5
1
3
4
1
2
3
1
2
1
0
1
E L E C T R I C
E X P A N S I O N
VALVE
• To drive the expansion valve, use the B-12 V output. Use a 4-phase coil and feed power to the phases
1 and 2, then switch over the filed poles to control the opening of the valve.
• The reference between conducting phase switch over direction and the open/close direction are
shown in Table 7-1. When the power is turned on, approx. 0.9 V is applied to the CN15 and the pins
(① to ④) and when no power is supplied, 12 V is applied. When the power is reset, the expansion
valve starts initial operation for 5 to 10 seconds.
• During the initial operation, measure each pin of the CN15 (① to ④) with a multimeter. If no change
is found around 0.9 V or 12V in this step, the expansion valve or the microcomputer has failure.
• The logic waveform during the operating of the expansion valve is shown in Fig. 7-2.
Table 7-1
CN15
pin#
④
③
②
①
Operation mode
④
③
②
①
9
1
2
3
4
5
1
6
7
8
I C 1 1
B − 0 V
Lead
wire
1
2
ON
ON
OFF
White
OFF
ON
Yellow
Orange
OFF
OFF
OFF
OFF
OFF
OFF
Blue
1→2→3→4→5→6→7→8 VALVE CLOSE
8→7→6→5→4→3→2→1 VALVE OPEN
50ms.
5 V
P Q 4 0 1
R219
R219
4 8
R220
R220
P Q 4 0 2
4 7
R221
R
2
2
1
P Q 4 0 3
4 6
R 4 2 4
R222
P Q 4 0 4
4 5
Fig. 7-1
Driving state
3
4
5
6
OFF
OFF
OFF
ON
ON
OFF
OFF
ON
ON
ON
OFF
OFF
ON
75ms.
200ms.
Fig.7-2
69
M I C R O
I C 2
C OM P U T E R
1 3
4
3 4
VALVE4
VALVE3
1 4
3
3 2
1 5
2
3 0
VALVE2
2 9
VALVE1
1 6
1
7
8
OFF
ON
OFF
OFF
OFF
OFF
ON
ON
12V
0.9V