SIN2008

Electrical basic
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Electric Basic (DX225LCA)

Target

- Understanding voltage, current and resistance

- Understanding symbol of electric components
- Understanding character of general electric components

Contents

- Electric basic (Voltage, current, resistance)

- Electric symbol and detail
Electric Basic

Voltage (Denoted : V)

Electric potential difference between positive (+) and negative(-) points and it is similar as a pressure
on hydraulic system.
•Generally, most of machine uses D.C. Voltage(12V or 24V)
•Charging voltage is 13.5V ~14.5V / 27.5V ~28.5V

Low voltage

Low voltage

High voltage

High voltage
Electric Basic

Current (Denoted : A)

A flow of electric charge and it is similar as a flow on hydraulic system.(Units : A or mA)

Pump Pump

High current / Big amount flow Low current / small amount flow

Depends on size of pipe (resistance of pipe line size) or water level

Electric Basic

Current (Denoted : A)

Flow of electricity through cable or wiring (how much flow does go though wiring) with specific time
In order to check amount of flow, the flow could be go through measuring tools
On the machine, the value could be measure as 0 mA(0.0A) ~ 700 mA (0.7A)

Wire
Electron

Flow of current
Flow of electron
Electric

Resistance (Denoted : Ω Ohm)

Difficult of oil flowing due to inside of resistance in the line, electric is almost same, the Ohm is how
difficult flow goes though the line

On the machine, Solenoid coil or auxiliary resistance could be measured with 10 Ω or 30 Ω

High resistance / low amount flow Low resistance / high amount flow

Depends on size of pipe / length of pipe resistance

What about pressure?

Wire Color

Doosan electrical drawing system only

Electrical Symbol

Not connected wire Not connected wire Connected wire

Electrical Symbol

Fusible link Circuit breaker 12 Volt power socket

Electrical Symbol

X X
O O (Above 3.3 Volts)
X (Below 3.3 Volts)
Diode Zener Diode Relay
Electrical Symbol

M
Pressure switch Fuse Motor
Electrical Symbol

Illuminate (Diode) light Pressure sensor

Cigar lighter
Electrical Symbol

Proportional valve Solenoid valve Temperature sensor

Electrical Symbol

Master Switch (-) Ground Buzzer

Electrical Symbol

Indicator Fuel sensor Shield

Electrical Symbol

Resister WIF sensor Switch

Electrical Symbol

DC/DC Convertor Check connector Hour meter

Fusible Link

Some circuits use fusible links, or fuse links, for overload protection.
Toyotas can have as many as six fusible links protecting circuits for
charging, starting, ignition, and certain accessories. Check the “Power
Source” page in the Electrical Wiring Diagram manual for the specific
vehicle.
Fusible link A fusible link is a short length of smaller gauge wire installed in a
circuit with larger conductors. High current will melt the link before it
melts the circuit wiring. Such fuse links have special insulation that
blisters or bubbles when the link melts. A melted link must be replaced
with one of the same size after the cause of the overload has been
identified and the problem corrected.
The fusible link is placed near by battery box
Circuit Breaker

Circuit breakers are used for protecting circuits temporary overloads

may occur and where power must be quickly restored. A bimetal strip
is used, similar to that in a temperature-sensitive switch. When
heated, the two metals expand differently and cause the strip to
bend. The “breaker” is normally closed and it opens when the bimetal
Circuit breaker element bends. Some circuit breakers are self-resetting, others must
be manually reset. (Near by battery )
Fuse

Fuses are the most common circuit protection device. Fuses have a
fusible element, or low-melting-point metal strip, in a glass tube or
plug-in plastic cartridge. These fuses are located in a fuse block
under the dash or behind a kick panel. Most circuits – other than the
headlamp, starter, and ignition systems – receive power through the
Fuse fuse block. Battery voltage is supplied to a buss bar in the block.
One end of each fuse is connected to this bar, the other end to the
circuit it protects.
Pressure Switch

The switch is activated by pressure (on or off position with set

pressure)
N.O. N.C. There is two kind of pressure switch as Normal Open (N.O.) and
Normal Close (N.C.)
Diode

Diodes are semiconductor devices which act as one way electrical check
valves. Diodes will allow current flow in one direction (anode to cathode),
X but block it in the reverse direction (cathode to anode).
O The diode is placed near relay or solenoid valve

Diode

Symbols for various diodes are shown. The arrow points in the “forward”
direction of current flow (anode to cathode). Zener diodes have a “Z”
X shaped bar on the cathode side. LEDs and photodiodes are enclosed in
O (Above 3.3 Volts) a circle with incoming or outgoing light indicated.
X (Below 3.3 Volts) The diode is placed near battery realy.
Zener Diode
Relay

In operation, when the control circuit switch is open, no current

flows to the relay. The coil is not energized, the contacts are open,
and no power goes to the load. When the control circuit switch is
closed, however, current flows to the relay and energizes the coil.
The resulting magnetic field pulls the armature down, closing the
Relay contacts and allowing power to the load.

* Question
1) When the switch is open, which lamps are lit?
2) When closed, then?
Proportional Valve

The proportional is activated with current value generally, one oil

line goes to proportional valve block and it controls (secondly) out
put pressure proportinally with current value. Doosan uses two
kinds of proportional valve on hydraulic system.

Positive curve type Negative curve type

Pressure Sensor

Physical pressure could be transferred electrical signal and it

would be measured with output voltage value from pressure
sensor, the output value is depends on pressure

Supply voltage : 10 ~ 30 DCV

Out put voltage : 1~ 5 V DCV
Ground
Solenoid Valve

The solenoid is activated with eclectic power and it becomes

magnet when the eclectic power (voltage) is supplied.
(The solenoid valve activities with ON or OFF function)
Temperature Sensor

The temperature is measured by resistance value

(High Temp. Low resistance value)
Temperature Switch

Temperature-sensitive switch – a bimetal element bends

when heated to make contact completing a circuit or to break
contact opening a circuit. The same principle is also used in
time-delay switches and flashers.
Switch

The switch is activated manually by operator (on or off)

There is many kind of switch as fixed position and return activate,
normal connect or open.
WIF Sensor

Water in fuel sensor is placed on fuel water separator bottom on

fuel line, it is one of variable resistance sensor, the out put value
is changed depends on medium of diesel or water in bottom cap.
EPOS/ VCU senses the value of WIF and gives information to
operator through monitor panel

WIF sensor
Motor

Motor is converting electric energy to mechanical energy

(Rotating) by magnetic force of current flowing on rotor.
The machine uses the electric motor as wiper, AC blower, throttle
M and engine stop system.

Motor

Spin

Current
Illuminate (Diode) light

LED (Light Emitting Diode) is converting electric energy to light

energy with semi-conductor
Recently the machine uses LED for head lamp,working lamp
including illuminate on switch in cabin

Illuminate (Diode) light

Buzzer

Buzzer makes sound or ringing with vibration

The machine uses it for warning (system problem) to operator in cabin
or working/operation warning to workers nearby machine

Buzzer

Convert electric energy to heat energy

Cigar lighter
Shield

Shield protects against any electric noise or unexpected effect

while current flowing on wire or cable, on the machine, CAN
communication components are there, communication signal of
CAN components are very sensitive from electric noise,
In order not to do wrong communication or giving wring signal,
to each components, need noise protecting stuff.
Shield

G/P

EPOS
Indicator

Indicator is one of pressure switch(sensing negative pressure), it

is placed on near air filter, Intake air pressure is lower then
specific value with specific time, warning to operator to check the
filter due to filter is clogging

Indicator
12V Power Socket

Power socket is for charging small capacity of electric

components (mobile phone)
Never use/charging over 7 A capacity of electric components

12 Volt power socket

Fuel Sensor

Fuel sender is one of variable resistance, the resistance value is

changed depends on float/Fuel level position (Fuel level in tank)
The EPOS takes the resistance value and display the fuel level
on monitor panel to the operator

Fuel sensor

Floating position F 3/4 1/2 1/4 E

Resistance (KΩ) 0.50 1.20 2.68 3.94 5.00
Voltage (DC) Full : 0.5~1.5V DC / Empty : 2.5~4.5V DC
Tolerance (KΩ) ± 0.5%
Let’s try to check mentioned components on machine

And check the symbol on electrical schematics at

machine.
COURSE SUMMARY – Electric Basic

Thank you for your attention

• In this course, you have

☞ Electric basic of Doosan DX225LCA Excavator

Continue to ‘Course survey’ & ‘Quiz’ to complete the course.