16
Automatic Control
APPENDIX B
Hydraulic Valve Guide
PT - Proportional Time Valve:
PT - Proportional Time Valve:
The PT valve, sometimes referred to as on/off or "bang-bang" valve is not a true proportional
valve. It can only be turned on or off.
The proportionality is achieved by rapidly turning the valve on and off over time at varying duty
tionality is achieved by rapidly turning the valve on and off
tionality is achieved by rapidly turning the valve on and off
rates as shown in the chart below.
Lower
Correction
Raise
Correction
On Grade
Deadband
0%
50%
100%
Valve Min.
Correction
Gain = 1
Gain = 1
Gain = 8
Gain = 8
Gain = F
Gain = F
PT Valve Signal
(% On, Duty Cycle)
Full machine voltage is applied to the valve to turn it on.
To achieve desired fl ow rates at "100% on" corrections, proper sizing of the valve or a fl ow
control device is required.
Application Note: These valves as a group are least expensive, but control performance is not
as smooth as with the PC or PV valves.
Since this type of valve pops open or closed over time, the hoses can jump about and the
rushing hydraulic fl uid actually make a snapping sound, hence the name "bang bang" valve is
often used.
PT Valve Wiring:
PT Valve Wiring: (P/N ATI-026040-XX)
1
2*
GND
Danfoss PT
Hirschmann Connector
1
2*
3 or 4
Danfoss PT
Amp Connector
*Raise cylinder port is the port closest to black electronics module.
Lower
Ground
A
B
C
D
E
F
G
H
I
J
Raise
Load Sense
Raise
Coil
Lower
Coil
M
CB
1
or
M
CB2
10-Socket
Connector
Blue
Green
Red
Orange
White
Black
White/Black
Switched Power
Ground
Not Used
