Basic Electronics OTOMOTIF DIODA

7/27/2019 Basic Electronics OTOMOTIF DIODA

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Solid State UniversityUnderstand the following components:PotentiometersThermistors

Capacitors

Diodes

Zener Diodes

Transistors


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Potentiometers

Differentiate between potentiometers

and rheostats

A rheostat changes current flow in a series circuit

A potentiometer is a voltage sensor in parallel


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Rheostat

Less resistance


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Rheostat

More resistance


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Potentiometer


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4 volt

PotentiometerVery low current


7/682 volt

PotentiometerUsed as a sensor


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2.5 volt

(should be 2 volt)

Potentiometerpoor ground


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5 volt

(should be 2 volt)

Potentiometeropen ground


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Rheostats are wired in series with the load

their purpose is to change amp flow

Potentiometers sense motion

check for: reference voltage

good ground

un-interrupted signal


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5.03 V5.02 V4.51 V4.51 V0.01 V0.01 V


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4.52 V0.52 V


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0.52 V0.0 V MIL lamp lit. TPS code

What is wrong?


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Thermistors

Thermistors change resistance with temperature

Negative Temperature Coefficient thermistors decrease in resistance

when they heat

Commonly used to sense changing temperatures


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High Resistance

when Cold!


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Low Resistance

when Hot!


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4.52 VHot or Cold?COLD!


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1.53 VHot or Cold?HOT!


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1.45 V1.15 V

Gauge reads colder than actual temperature


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0.49 V0.02 V



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0.47 V



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Thermistors

Thermistors are checked with an Ohmmeter or a Voltmeter

A temperature probe or thermometer should be used when

checking


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Capacitors

Capacitors store an electrical charge

Capacitors provide an alternate path for electrons and act as a current

shock absorber

Capacitors are commonly used to suppress noise

alternators

coils

motors


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Capacitors

Capacitors are rated in microfarads

Capacitors are connected in parallel

with a load

they can be checked with an ohmmeter for short or open

circuits


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Find the

Capacitor


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EMI & RFI

When coils turn off they self induce and create a voltage surge

this surge can create electromagnetic interference and radio frequency

interference

capacitors absorb this surge to dampen interference


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Semiconductors

Conductors have 3 or fewer electrons in the valence ring of

the atom

copper has one

aluminum has three

Insulators have 5 or more electrons in the valence ring of the

atom


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Semiconductors

Elements with four valence electrons are not good as

insulators or conductors

Silicon, when is a crystal form, shares valence electrons to

make a good insulator

Silicon can be doped to add electrons to the valence ring or

remove electrons from the valence ring


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Semiconductors

Silicon doped with phosphorous (which has five electrons in

the valence ring)will create an N type semiconductor

Silicon doped with boron (which has three electrons in the

valence ring)will create a P type semiconductor


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Diodes

Placing an N type semiconductor with a P type will create

a diode.

In a forward biased diode current will flow with a small

amount of resistance

Too much current will overheat and destroy the diode


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Diodes

Reverse biasing a diode will create very high resistance at the center

of the diode and current will not flow

Too much voltage will overcome the internal resistance and thediode will short out


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12.6 V0.0 V

Arrow shows conventional theory (hole flow)

Diodes wired like this will block current


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Arrow shows conventional theory (hole flow)

Diodes wired like this will allow current to

flow with a slight voltage drop

12.6 V12.0 V0.1 V


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Testing Diodes

Diodes require .2 - .6 volts to forward bias

Digital ohmmeters may not supply this voltage with ohm

check

use diode check feature when using DVOM


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Testing Diodes

Shorted diodes on alternators will allow A/C voltage that may

confuse a control module

Routine checks with oscilloscope are easy


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Anti- Spike Diodes

Clamping or Anti-Spike diodes protect sensitive control modules


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Anti- Spike Diodes

Functioning anti spiking diodes will exhibit

un-equal resistance when reversing polarity (using an analogue

meter)


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Failure in Anti- Spike Diodes

An open, or shorted diode will damage computer control modules

Open diodes allow spike voltages to harm electronic components

Shorted diodes (and relay coil windings) will cause too much current

to flow and burn out switching transistors in computers


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Testing Anti- Spike Diodes

Open diodes will show equal resistance with reversed polarity

(using an analogue meter)

Shorted diodes will show equal, and low resistance


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Open Diode


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Shorted Diode


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Good Diode


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Good Diode


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Types of Diodes

Positive diode

Negative diode

Zener Diode

Light Emitting Diode (LED)


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Transistors

Transistors can act as a relay

they use a small signal current to control

a larger working current

Transistors can act as a signal amplifier


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PNP transistor

Points InPermanently

Will conduct current when the base sees a Negative polarity


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NPN transistor

Never Points In

Base must be Positive to allow transistor to conduct current


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Transistors

Transistors are damaged by too much current

Transistors are damaged by high voltage


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Basic Electronics OTOMOTIF DIODA

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