JLG 450AJ Service Manual - Manual (Page 70)

SECTION 2 - PROCEDURES
2-54 – JLG Lift – 3120869
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.
Dual Range
This Rotary Selector Controller is capable of providing
two, independently adjustable, maximum output ranges
with the same amount of handle travel. The Hi Range
would normally be adjusted for full flow (maximum func-
tion speed) of the valve at full handle travel. The LO Range
would provide some portion of the Hi Range setting, pro-
viding reduced oil flow to the valve, with the handle at full
travel. LO Range provides the operator with excellent con-
trol of the proportional function with increased resolution
for precise maneuverability. Both outputs are linear
between the Threshold setting and their respective set-
ting. The Rotary Selector Controller is in the Hi Range
mode when 12 volts is applied to the (R) terminal. As a fail
safe, when system voltage is removed from the (R) termi-
nal, the Lo Range feature is active.
I.R.S (Integrated Ramp System)
This Rotary Selector Controller is calibrated to provide a
maximum ramp time of 3 seconds. This feature limits the
rate of change of the output, eliminating a jerky response
associated with sudden handle movements. Any change
in handle position will result in a smooth change in func-
tion speed. The 3 seconds is measured between the
Threshold and Hi or LO range setting.
Adjustment Procedure
NOTE: The trimpot adjustment screws are multi turn
devices. No harm can come to the trimpot if it is
turned too much. The trimpot will "click" when the
wiper is at the end of the element. It may be neces-
sary to turn the adjustment screw several turns to
observe a change in the output.
1. Disconnect the output wire from the card to terminal
12. Install a volt-ohmmeter in series in this wire and
set the volt-ohmmeter to mA.
2. Turn on all power; engine does not need to be run-
ning.
3. With the function speed switch turned to the fully
CCW position, activate the Telescope out switch and
adjust Threshold to 300 mA.
4. With the function speed switch turned to the fully
CW position, activate the Telescope out switch and
adjust Hi Range to 1100 mA.
5. With the function speed switch turned to the fully
CW position, activate the Platform Rotate switch and
adjust Lo Range to 800 mA.
6. Set Ramp about 10 turns CW from the fully CCW
position.
Figure 2-37. Function Control Card Adjustment
Updated 10-12-99