CHAPTER 5CHAPTER 5
RESISTORSRESISTORS
USES OF RESISTORS
1. LIMIT CURRENT FLOW
2. ACT AS A VOLTAGE DIVIDER
I= E/R = 15V / 30 OHMS= .5 AMPS
I= E/R = 15V / .0001 OHMS = 150000 AMPS
I=E/R=17.5/300= .05AMPS
A TO B (E=I x R=.05Ax30 OHMS= 1.5V)
B TO C (E=I x R=.05A x 120 OHMS = 6V)
C TO D (E=I x R= .05 x 200 OHMS = 10 V)
FIXED RESISTORSFIXED RESISTORS
HAVE ONLY 1 OHMIC VALUE HAVE ONLY 1 OHMIC VALUE WHICH CANNOT BE CHANGEDWHICH CANNOT BE CHANGED
TYPES INCLUDE COMPOSITION TYPES INCLUDE COMPOSITION CARBON, METAL FILM, CARBON CARBON, METAL FILM, CARBON FILM, METAL GLAZE, AND WIRE FILM, METAL GLAZE, AND WIRE WOUND WOUND
RESISTOR POWER RATINGS
IF POWER RATING IS EXCEEDED= LET THE SMOKE OUT IT
MOST COMMON TYPE: MADE OF CARBON GRAPHITE AND A RESIN BONDING MATERIAL
INEXPENSIVE: HAVE RANGE OF 1 TO 22 MEGOHMS POWER RATINGS OF 1/8,1/4,1/2,1,AND 2 WATT
TOLERANCE RANGES OF 20%, 10%, 5%
WIRE WOUND RESISTORS
*MADE BY WINDING A PIECE OF
RESISTIVE WIRE AROUND A CERAMIC CORE
*USED WHEN A HIGH POWER
RATING IS NEEDED
*ALLOWS AIR TO COOL BY FLOWING THROUGH IT
*SHOULD BE MOUNTED VERTICALLY: CHIMNEY EFFECT
STEPPED WIRE WOUND USED ON BLOWER MOTORS TO CONTROL SPEED
1st Band: 1st Number
2nd Band: 2nd Number
3rd Band: Multiplier
4th Band: Tolerance
If it has 5th Band: 1% Tolerance
If a resistor is replaced, use same tolerance& equal value
1500 ohms with 10% tolerance
VARIABLE RESISTORSVARIABLE RESISTORS
A RESISTOR WHOSE VALUE CAN A RESISTOR WHOSE VALUE CAN CHANGED OR VARIED OVER A CHANGED OR VARIED OVER A RANGERANGE
AVAILABLE IN DIFFERENT CASE AVAILABLE IN DIFFERENT CASE STYLES AND POWER RATINGSSTYLES AND POWER RATINGS
TYPES INCLUDE RHEOSTATS, TYPES INCLUDE RHEOSTATS, POTENTIOMETERS, THERMISTORS, POTENTIOMETERS, THERMISTORS, PHOTO-RESISTORSPHOTO-RESISTORS
RHEOSTATSRHEOSTATS
TWO WIRE VARIABLE RESISTORTWO WIRE VARIABLE RESISTOR HAS MOVEABLE LEVER THAT HAS MOVEABLE LEVER THAT
VARIES RESISTANCEVARIES RESISTANCE EXAMPLES: DASH LIGHTS DIMMER, EXAMPLES: DASH LIGHTS DIMMER,
FUEL SENDING UNITS, WIPER FUEL SENDING UNITS, WIPER DELAY SWITCHES DELAY SWITCHES
POTENTIOMETERSPOTENTIOMETERS
THREE WIRE VARIABLE RESISTORTHREE WIRE VARIABLE RESISTOR USED AS A POSITION INDICATOR USED AS A POSITION INDICATOR
(INPUT TO A LOGIC DEVICE)(INPUT TO A LOGIC DEVICE) EXAMPLES: THROTTLE POSITION EXAMPLES: THROTTLE POSITION
SENSOR (TPS), EGR POSITION SENSOR (TPS), EGR POSITION SENSOR, HVAC DOOR POSITION SENSOR, HVAC DOOR POSITION SENSORSENSOR
THERMISTORSTHERMISTORS
TWO WIRE SENSORSTWO WIRE SENSORS RESISTANCE VARIES WITH TEMPRESISTANCE VARIES WITH TEMP CAN BE “PTC” OR “NTC”CAN BE “PTC” OR “NTC” USED AS INPUT TO A LOGIC DEVICEUSED AS INPUT TO A LOGIC DEVICE EXAMPLES: COOLANT TEMP EXAMPLES: COOLANT TEMP
SENSOR, INTAKE AIR TEMP SENSOR, SENSOR, INTAKE AIR TEMP SENSOR, BATTERY TEMP SENSOR, IN CAR BATTERY TEMP SENSOR, IN CAR TEMP SENSORTEMP SENSOR
PHOTO RESISTORSPHOTO RESISTORS
TWO WIRE VARIABLE RESISTORSTWO WIRE VARIABLE RESISTORS RESISTANCE CHANGES WITH RESISTANCE CHANGES WITH
DIFFERENT LEVELS OF LIGHT DIFFERENT LEVELS OF LIGHT INPUTINPUT
EXAMPLES: AUTOMATIC EXAMPLES: AUTOMATIC HEADLIGHTS, SUNLOAD SENSORS HEADLIGHTS, SUNLOAD SENSORS ON HVAC SYSTEMS, ASSEMLY LINE ON HVAC SYSTEMS, ASSEMLY LINE SWITCH INPUTSWITCH INPUT
REVIEWREVIEW 1. NAME TWO 1. NAME TWO
FUNCTION OF FUNCTION OF RESISTORS?RESISTORS?
2. WHAT IS FIXED 2. WHAT IS FIXED RESISTOR?RESISTOR?
3. NAME THREE 3. NAME THREE TYPES OF FIXED TYPES OF FIXED RESISTORS?RESISTORS?
4. WHAT EFFECTS 4. WHAT EFFECTS POWER RATING?POWER RATING?
5. 5. NAME AN NAME AN ADVANTAGE OF ADVANTAGE OF WIRE WOUND WIRE WOUND RESISTOR.RESISTOR.
6. WHAT ARE THE 6. WHAT ARE THE COLORS FOR?COLORS FOR?
7. WHAT IS A 7. WHAT IS A VARIABLE VARIABLE RESISTOR?RESISTOR?
8. NAME THREE 8. NAME THREE TYPES OF VAR. TYPES OF VAR. RESISTORSRESISTORS..
THAT’S ALL FOLKS!!!THAT’S ALL FOLKS!!!