JLG 120-SXJ ANSI Service Manual - Manual (Page 49)

SECTION 3 - CHASSIS & TURNTABLE
3121105 – JLG Lift – 3-21
Telescope, Level, Rotate, & Jib
1. Connect Amp Meter inline between the function card
plug pin #4 and red/wht 50-1 wire.
2. Turn function control knob fully CCW (Do not go into
snail mode). Operate telescope switch and adjust
threshold trimpot.
3. Fully turn knob CW operate the telescope siwtch.
Adjust HI range trimpot.
4. With the knob turned fully CW, operate the level
switch. Adjust the LO trimpot.
5. Adjust ramp trimpot to provide a smooth start and
stop function.
Drive
1. Connect Amp Meter inline between the drive control-
ler plug pin #2 and orange 8-1 wire.
2. Operate the drive controller forward until the red
LED glows. Adjust threshold trimpot.
3. Fully stroke controller. Adjust the HI range trimpot.
4. Turn function speed control CCW to snail position.
Fully stroke controller and adjust the LO trimpot.
5. Adjust the ramp trimpot to provide a smooth start
and stop function.
3.11 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 turn the knob, the electronics
change the time period the pulse is on within that cycle.
As you move the knob away from the slow position, the on
time period or width of the cycle pulse will increase and as
you move the handle back towards the slow position, 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.
Table 3-1. Controller Settings
Function
HI LO THRES
Lift 900 200 100
Swing 500 180 140
Telescope, Rotate, Level,
& Jib 900 230 150
Drive 140 70 12