JLG 450AJ ANSI Service Manual - Manual (Page 86)

SECTION 2 - PROCEDURES
2-68 – JLG Lift – 3120749
2.26 LIFT AND SWING CONTROLLER
Adjustment
NOTE: The following procedures are for a preliminary
adjustment. Final Adjustments are to be based on
the function speed of the operation.
Lift Swing and function speed control are all adjusted to
the same values. Threshold 300ma, Low Range 800 ma,
and Hi Range 1200 ma.
1. To adjust Lift and Swing Threshold, and Hi Range
trimpots, Pin 5 on the control card requires 12 volts.
2. To adjust the Low Range trimpot, Pin 5 requires no
voltage.
3. The function control switch turns power on and off at
Pin 5.
4. To check and adjust milliamps on Lift Up and Down,
connect an amp meter inline between the tan lines
at terminal strip #8.
5. Turn the function speed switch past the snail posi-
tion, operate the Lift joystick just past the Off posi-
tion in both directions.
6. Adjust the Threshold trimpot to 300 ma.
7. Fully stroke the joystick and adjust the Hi Range
trimpot to 1200 ma.
8. Turn the function speed control to snail position and
fully stroke the joystick and adjust Lo Range trimpot
to 800 ma.
9. To adjust swing left and right connect the amp meter
inline between the white wires at terminal #9. Per-
form adjustment steps the same as outlined for Lift.
2.27 FUNCTION CONTROL
Rotary Selector Controller Theory &
Definitions
This Rotary Selector Controller is specifically designed
and manufactured to provide a proportional output to a
HYDRAFORCE flow control electro-hydraulic valve. The
Rotary Selector Controller you are about to calibrate has
the following features:
PWM Output (Pulse Width Modulation)
The HYDRAFORCE valve being driven by this Rotary
Selector Controller requires an electrical current, between
360 and 1400 milliamps in order to shift the valve spool
from minimum to maximum flow. Because of the mass of
the spool, shifting it a very small distance would be very
difficult to do without overshooting the mark. This over-
shoot is called hysteresis and makes precise control of
the function very difficult. PWM output provides a pulsed
current to the spool which actually vibrates the spool so
that it is never at rest and very easy to shift. This Rotary
Selector Controller pulses the spool 130 times (cycles)
per second and as you move the handle, the electronics
change the time period the pulse is on within that cycle.
As you move the handle away from center, the on time
period or width of the cycle pulse will increase and as you
move the handle back towards the center, the pulse will
decrease. The percentage of on time to off time of the
PWM signal is called the Duty Cycle, if it is on for 80% we
call that an 80% duty cycle.
Current Regulated Output
This Rotary Selector Controller output is also current regu-
lated. This Rotary Selector Controller was designed to out-
put from 360 to 1400 milliamps through a 4.7 ohm coil
using a 12 volt supply. Ohms Law dictates that the Current
is always equal to Voltage divided by Resistance. If the
supply voltage or the coil resistance should change,
Ohms Law dictates that the output current must also
change which will affect the speed of the function accord-
ingly. Because this Rotary Selector Controller is equipped
with a current regulated output, it senses a change in volt-
age or resistance in the circuit and adjusts the duty cycle
of the PWM signal so that the output current remains a
constant current. Because the Current is constant and
Resistance is machine dependent, the duty cycle will vary
in an attempt to supply the required level of output. This
feature ensures that the function speed the operator
wishes to select always remains the same, within the limits
of Ohms Law.
Figure 2-38. Lift and Swing Adjustment