Temperature And Latch; Hot Switch Inverter; Aid System Card Enclosure - Komatsu 930E-2 Shop Manual

FIGURE 3-2. AID SYSTEM CARD ENCLOSURE
1. Diode Matrix With Sound
2. Diode Matrix Without Sound

3. Hot Switch Inverter

4. Hot Switch Inverter (Not Used)
5. Temperature & Latch
6. Coolant Level & Flasher
The other half of the circuitry on the Coolant Level and
Flasher Card operates the Coolant Level Light. The
Water Level Probe connected to terminal B11 grounds
the 31L circuit when the coolant in the radiator is above
the probe position. The coolant saturates the probe
and electrically grounds the circuit. When the circuit is
grounded, Q6 transistor is off, resulting in no indication.
When the coolant level drops below the probe, 31L is
no longer grounded and Q6 turns on to ground the
flasher through D5, ground the Coolant Level Light
through terminal D11, and ground the alarm horn
through D6. The light and alarm horn will operate
intermittently as their 24 volt supply is from circuit 12F,
the flasher output.
NOTE: Some electronic engine controls monitor cool-
ant level. If the engine controls monitor the circuit, a
2KΩ resistor is installed to replace the probe and
disable the AID system circuit.
D3-4

Temperature and Latch

The Temperature and Latch Card has two circuits to
operate two different indicating lights. The temperature
circuit is controlled by a coolant temperature sensor
which decreases electrical resistance as its tempera-
ture increases. It will have a resistance of approxi-
mately 1000 ohms at 185
o
250 F (122
When the temperature is low and the resistance is high,
Q1 is off and no high temperature indication occurs.
When the coolant temperature is excessive, resistance
decreases to a point where Q1 will turn on and ground
the flasher through D8, the alarm horn through D12,
and the High Temperature Light through terminal D8.
R14 can adjust the temperature (resistance) at which
the circuit is activated.
NOTE: Some electronic engine controls monitor cool-
ant temperature. If the engine controls monitor the
circuit, a 2KΩ resistor is installed to replace the tem-
perature sensor and disable the AID system circuit.
The Latch Circuit monitors the accumulator precharge
pressure switches. When one of the pressure switches
closes, Q5 will be turned off which supplies power to
the gate of SCR Q7. With Q7 turned on, Q9 will supply
the ground path to turn on the Low Accumulator Pre-
charge Indicator Light and sound the alarm horn. The
Indicator Light is connected to 12F and will flash off and
on. The SCR will remain on until power is removed from
the card by turning the key switch "Off".
Hot Switch Inverter
The Hot Switch Inverter Card (Slot 3) is used to operate
and test the service brake indicator light. In normal
conditions Q4 transistor is off and the Indicator Light is
off. When the stoplight switch is activated, 24 volts is
sent to pin "E" of the Hot Switch Inverter Card. Tran-
sistor Q4 is turned on by this voltage and, in turn,
grounds the service brake Indicator Light. There is no
alarm horn operation with this card.
A second circuit on this card is used to operate and
test the Retard Speed Control indicator light. When
RSC is turned Off, transistor Q7 is off and the indicator
light is off. When RSC is turned on, 24 volts is sent to
pin "J" of the card. This voltage turns on Q7, grounding
the indicator light circuit.
24VDC System Components
o o
F (85 C) and 500 ohms at
o o
C). Normal setting is 204
o
F (96 C).
D03019 04/01