Technical information

Appendix B: Touble Shooting 38

DRV Operator’s Manual and Technical Reference (rev 1 0 June 30, 2000)

Never use a test light to check an output. Unexpected motion can result causing

personal injury and/or damage to the equipment. If a test light were connected

between the groundside of the load and ground, the load would be in series with the

light and the circuit completed. The low impedance of the test light may allow

enough current to flow to drive the output device. The dump body valves are driven

by the digital outputs via a set of relays. The relays require little power and could

easily be driven. Always use a digital voltmeter to check all voltages on the control

system.

The dump body valves are driven off of the digital outputs via the control relays. The

control relays coil is supplied with a +12 VDC voltage and the controller sinks the

current to ground. The pole of the relay is +12 VDC and switched to energize the dump

body valves. For each valve there are two relays, a primary and secondary. The

secondary relay determines which direction the valve is to be driven. The primary relay

supplies the +12 VDC to the pole of the secondary relay and serves as an on/off switch.

An example of an open collector output is illustrated in Figure B.2. Refer to the wiring

diagrams, Appendix C, for details.

+ 12 VDC

LO AD

DIODE PRO TECTION

LOGIC GATE

OUTPUT

BASIC OPEN COLLECTOR OUTPUT

Figure B.2

B.1.4 Analog Outputs

The analog outputs are used to drive the Pulse Width Modulating (PWM) Amplifiers.

The analog outputs from the D-A expansion board vary nominally from 0 to +10 VDC.

To verify that the analog output is working a voltage reading, utilizing a digital voltmeter,

can be taken while the joystick is being swept. This can be accomplished with the truck

engine turned off such that the hydraulics are non-operational, accessory power on, and

the controller energized and in the system ready state. On each amplifier board there is a

LED next to each output transistor. Therefore to verify that the amplifiers are working,

check that the output LED’s on the PWM boards are lighting as the corresponding input

channel is set active. For example, if the joystick commands that the short arm be driven

then the LED corresponding to the short arm channel should light up.