Switch Wiring - Low Side, High Side - JLG 1930ES Service Maintenance Manual

3. Operate system such that the switch actuates. This could be going over a certain pressure or temperature, for exam-
ple. The state indicated in the control system should change.

Switch Wiring - Low Side, High Side

When controlling a load, a switch can be wired between the positive side of the power source and the load. This switch is
called a "high side" switch. The switch supplies the power to the load. When a switch is wired between the negative side
of the power source and the load, it is a "low side" switch. The switch provides the ground to the load.
A low side switch will allow voltage to be present on the load. No power is applied because the switch is stopping current
flow. This voltage can be seen if the measurement is taken with one test lead on the load and the other on the battery
negative side or grounded to the vehicle. What is actually being measured is the voltage drop across the switch. This
could mislead a technician into thinking the load is receiving power but not operating. To produce an accurate picture of
power or voltage applied to the load, measure voltage across the load's power terminals. Also, the technician can mea-
sure the voltage at both power terminals with respect to battery ground. The difference between those two measure-
ments is the voltage applied to the load.
7.6 CIRCUIT BOARDS: INPUTS AND OUTPUTS
Pin
1
2
3
4
5
6
7
8
9
10 Left PHP Switch
11
12 CAN Bus Low
13 CAN Bus Shield
14 Analog Power
15 Elevation Angle Sensor
16 Ground
17 Ignition
18 Right PHP Switch
19 Ignition
20 Brake Release Swtich
21 Steer Left Coil
22 Steer Right Coil
23 Left Brake Release
24 Right Brake Release
25 Lift Up Coil
26 Lift Down Coil
27 Ground
28 Ground Alarm
29 Charger Interlock
30 Ground
31 CAN Bus High
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SECTION 7 - GENERAL ELECTRICAL INFORMATION & SCHEMATICS
Table 7-1. Ground Board J1 (1600346 Power Module ONLY)
Function
Ground
Analyzer Power
RS-232 Receive
RS-232 Transmit
Platform EMS
Ground
Ignition
Platform EMS Source
Ignition
CAN Bus high
Type
Power Output
Power Output
Input/Output
Input/Output
Input
Power Output
Power Output
Power Output
Power Output
Input
Input/Output
Input/Output
Power Output
Power Output
Input
Power Output
Power Output
Input
Power Output
Input
Output
Output
Output
Output
Output
Output
Power Output
Output
Input
Power Output
Input/Output
– JLG Lift –
Range (V)
0
12
Comm
Comm
Vbatt
0
Vbatt
Vbatt
Vbatt
Vbatt
Comm
Comm
0
5
5
0
Vbatt
Vbatt
Vbatt
Vbatt
Vbatt
Vbatt
Vbatt
Vbatt
Vbatt
PWM
0
PWM
Vbatt
0
Comm
7-13