ABS Demonstrators

Locate the wiring diagram for your demonstrator vechicle. Find the ABS wheel speed sensor pin out connections to the ECU on the wiring diagram and the demonstrator. Record which ECU wires go to which wheel speed sensors:

This demonstration is done on Mazda 323 JM BA

Left front: ECU Pin# 2O and 2P

Left rear: ECU Pin# 2R and 2Q

Right front: ECU Pin# 2N and 2M

Right rear: ECU Pin# 2S and 2T

By looking at the wiring diagram, what type of speed sensor is this?

It is a magnetic sensor, therefore its a four channel speed sensor which has individual sensor for each wheel.

Describe how it works:

It works according to the wheel sensor which approximately 1mm above the sensor rotor therefore when wheel rotates the pulse ring rotates as well. When each pulse ring passes under the sensor, a small voltage pulse is present in the sensor. Finally the pulse sents the input signals to the ECU.

Locate an oscilloscope. Turn it on and set it up to be fully operational. What oscilloscope are you using?

Digitech Dual-Channel Oscillioscope QC1992.

Record a waveform for each wheel speed sensor in the boxes below. Note voltage per division and time per division for each. Please don't keep the Abs units on very long because it drains the battaries.

Which wheel is this? Left Front 2O / 2P

Which wheel is this? Left Rear 2R / 2Q

Which wheel is this? Right Front 2N / 2M

Which wheel is this? Right Rear 2S / 2T

Are all the waveforms exactly the same? Yes or No. Discuss what are the differences, and what can cause these differences between the waveforms:

No, because the front and rear sensors provides different waveforms. The front right and front left sensors shows the amplitude reading of 0.6V whereas the rear right and the rear left reading were 0.4v but the frequency for both sensors are 0.38ms. Both the rotors have 44teeth but while checking resistance the front wheel is 0.430K and the rear wheel has 0.890K.

With the wheel speed sensors spinning, measure AC volts with a multimeter and record here:

Left Front - 3.17V

Left Rear - 2.68V

Right Front - 4.22V

Right Rear - 2.85V

Can a multi-meter be as accurate in finding problems with the wheel speed sensors as an oscilloscope? Yes or No.

No

Discuss what the oscilloscope could find that the multi-meter can not find and why:

The oscilloscope gives the visual reading of what is captured by the sensor, for example if there is a chip, dent, scratch or any type of damage on the the rotor teeth then the oscilloscope will detect and display broken lines or distorting lines and it will indicate the fault.

Wiring Diagram Practice

There are a number of components in the ABS systems that are also used for injection. These are mostly speed sensors e.g. wheel speed and engine speed.

Using the wiring diagram in the workshop manuals identify the wheel speed sensors and the list their wire colours for each sensor.

Front Right : Black/White

Front Left : Green/Red

Rear Left : Blue/Pink

Rear Right : Yellow/Brown

On th ABS wheel sensor what is the reason for the braded wire?

So it can be used for shielding purposes or used alone in flattened form as a grounding strap.

Advantages of the Braded wire.

1. Power -Braded wire can carry more power because it has a higher surface area. Each braded wire presents all sides that would be smashed against the center of the solid wire. Braded wire is also used to carry large amounts of power because it is easier to dissipate the heat that so much flowing electricity generates when there is space between wires.



2. Sound - solid strand wires are capable of carrying extremely high frequencies. These frequencies can be disrupted by imperfections on the surface of the wire, so solid wires perform better because they have less surface area. The only difference in sound is caused by the tiny air pockets between wires.



3. Flexibility - Braded wire is used for devices that need to be compact because of its greater flexibility. Car batteries are one of the most common devices that require tightly packed copper wire.

Identify and list all the fuses that are used by the ABS circuit.

F14 fuse box, FL main, Y-G, Gauge 10A, Dome 20A, STOP 15A (brake) and the ECU.

Identify the earths for the ABS control unit and ABS motor their wire colours what pins numbers.

The earths and the colours are 10B and 7B whereas the colour is white /black and the pin numbers and colours for ABS motor is 1A and the colour of the wire is white / black.

On the wiring diagram for the ABS actuator, identify which solenoids control which wheel cylinder. Then note the wire colours and pin numbers.

Front Right Wheel : Pin number - 2B/6B and the Wire colour - Red White / Red Green

Front Left Wheel : Pin number - 3B/7B and the Wire colour - Blue Red / Blue White

Rear Left Wheel : Pin number - 1B/5B and the Wire colour - Brown White / Brown Red

Rear Right Wheel : Pin number - 4B/8B and the Wire colour - Green Black / Green Yellow

Using the picture above as a guide, which of the following gives the correct condition of the inlet and outlet solenoids valves under normal braking?

B - inlet valve open and outlet valve closed.

Using the picture above as a guide, which of the following gives the correct conditions of the inlet and outlet solenoids valves when the ABS is operating to reduce wheel brake pressure?

C - inlet valve closed and the outlet valve open

Using the picture above as a guide, which of the following gives the correct condition of the inlet and outlet solenoids valves when the ABS is operating to hold brake preesure?

D - inlet valve closed and the outlet valve closed.

Using the picture above as a guide, which of the following gives the correct condition of the inlet and outlet solenoids valves when the ABS is operating to increase wheel brake pressure?

B - inlet valve open and the outlet valve closed.

In the four cases above state when the ABS motor will be working?

Case two: It will be working only to reduce the wheel brake pressure.

There are three main types of wheel sensors on modern vechicles. One sends an analogue signal using and inductive pick up, the others send a digital signal using ether hall effect or magneto-resistant encoder.

On the graph below draw a digital signal switches 5volts every 2 seconds. Mark volt and time scales on the graph that will show the signal well.

On the graph below draw an analogue signal with a frequency of 0.5Hz and a maximum of +3 volts. Mark volt and time scales on graph that will show the signal well.

ABS Wiring and Operation

Lets review the ABS system to remind ourselves what components are included ang how they should work.

1. Wheel



2. Wheel Speed Sensor



3. Pulse Ring



4. ABS / TCS / ECU



5. Master cylinder



6. Brake caliper



7. Brake Booster
   
   

Antilock Braking System (4825) Second Course

Off - Car Exercises

Think about ABS repair:

Misconceptions, The ABS system should be simple and robust, with the Module/ECU/Controller almost never giving any trouble.

Below are some possible causes for damaging an ECU.

• Spiked by careless welding, i.e. MIG welding without dissconecting the battery.

True

• Enclosure seal damaged and with obvious sign of water ingress.

True

• Obvious signs of mechnical damage to the enclosure.

True

Often the ECU will be misdiagnosed as faulty, usually because the technician is inexperienced in fault finding.

• Faults are much more likely to be with connections or sensors.

True

Discuss how this ECU issues should be incorporated into diagnostic practises to test and ABS system:

ABS controls the brake pressure at the wheels, therefore its purpose are stabilty and steerbility. During the braking session the ECU controls the wheel speed sensor.

Sensor Circuit Board Write-Up

Oxygen Sensor Circuit

Parts Lists

• D1, D2 and D3 1N4001 1000v silicon diode 0.7 forward biased
• Capacitors x2 Monolythic Dip C5K, 1uF
• LEDs Red, Yellow, Green 1.8volts
• R2, R3 and R4 resistor 1k
• R5 resistor 330R
• R6 resistor 10K
• R7 resistor 270R
• R8 resistor 470R
• Zener diode 9V1
• Integrated Circuit LM324AN 14pins
• Jumper wires

Calculations for resistors used in the Sensor Circuit

R2, R3 and R4 = 12- 0.7

= 11.3v - 1.8 = 9.5volts

= 9.5/0.095

= 1000

Therefore the preferred value resistor used is 1k

R5 = 11.3/0.330

=34.24

Therefore the preferred value resistor used is 330R

R6 = 10k

R7 = 0.23v/ 0.00091A

= 252ohms

Therefore the preferred value used resistors is 270R

R8= (0.63-0.23)/0.00091A

= 439.56ohms

Therefore the preferred value used resistor is 470R

How the sensor circuit works

Inorder to get this cicuit operational you need a 12volts power supply with the common or earth to get the first set of LED working (green). As the current flows through the first diode which uses 0.7volts passing through the capacitor(C1). The zener protection resistor (R5) reduces the current flowing to the zener diode which now regulates the voltage down to the 9.1volts. All currents going into the input of the Intergrated Circuit is later limited by the resistors 6, 7 and 8. Pins number 3, 6, 9 and 12 are the input sensor which is from 0.3 to 1.0volts maximum. The pin number 11 from the Intergrated Circuit is connected to the earth whereas the pin number 4 is connected to the 12v power supplied rail. Pins 2, 5, 10 and 13 are the (in) connected between two resistors and to earth. When you connect the input PL2 the green LED goes off and then when you adjust the voltage to 0.3volts the yellow LED lights up as increase from 0.3 to 0.7 volts the yellow LED goes off and the red LED lights up.

Fault Findings

After making this circuit I conected my circuit to the power supply and my circuit did not work because I did not separated the pins 2,5,10 and 13 from the pins 3,6,9 and 12 after fixing all that problem my circuit looked very untidy so I decided to make a new design and new circuit board. After i made my new circuit board i tested it and than it worked.

Test Procedure

To get this circuit working you need to have 12v power supply and additional 0.3 to 0.7volts is required inorder to allow the yellow and red LED to light up as you adjust your additional voltage. This will show you that the yellow LED switches with the red LED as u change the voltage.

Power Circuit Board Write-Up

Power Circuit

Parts List

• D1 1N4001 1000v silicon diode
• D2 1N4001 100v silicon diode
• Zener diode
• Capacitor electrolyte radial 25V 33uF x2
• Voltage regulator LM317T
• R1 resistor 1k
• R2 resistor 330R
• R3 resistor 100R
• LED 2.02v 30mA 5mm
• Jumper Wires x3
• Red lead 12volt outputpower supply
• Yellow lead 5volts output power supply
• Black lead Earth wire

Calculation for resistors used in the Power Circuit

R1 = 1k +/- 5% 0.5 watts

R2 = 330R +/- 5% 0.5watts

R3 = 100R = +/- 5% 0.5watts

Test Procedure

To make this power circuit working you need to have 12v power supply. This is connected to red lead (positve) and black lead (negative) of the power circuit, therefore when the 12v is linked then the Red LED should light up but not only Light up it should be able to get 5v output from the power circuit when the 12v is supplied.

How the circuit works

Inorder to get this circuit working 12volts power supply is needed. The first diode is in the 12volts positive rail which is in forward bias of 0.7v dropping the voltage to 11.3volts. The zener diode is also connected in the reversed biased direction passing through the capacitor which does not make any difference in regulating the voltage and links up with the voltage regulator. The adjust pin from the voltage regulator attaches to 1k resistor then to earth. 330R resistor is then connected from the 1k resistor to the output of voltage regulator. The capacitor 2 is now attached in the output rail from voltage regulator therefore the jumper lead is connecting from the output rail to the second diode which makes the circulation of power in the voltage regulator. Finally 100R resistors is now linked from the output rail to the LED to earth. This completes my circuit and it works leaving the three lead wires of 12v output, 5v output and grounding.

Fault Findings

In this circuit I did not have any faults because my circuit worked at the first attempt. Inorder to find the fault its must to check for volt across the components and to ensure that they are in good working condition.

Injector Circuit Board Write-Up

Injector Circuit




























































Parts Lists

• Vero Board
• Jumper wires x4
• R1 resistor 470R x2
• R2 resistor 47R x2
• Transistor NPN type BC 547 x2
• LED 1 2.02volts 5mm 30mA Yellow
• LED 2 2.02volts 5mm 30mA Clear but red when it lights up

Calculation for resistors used in this injector circuit

R1 = 12/0.03mA

= 400 ohms

Therefore preferred value is 470 ohms resistor

R2 = 5 - 0.7

= 4.3

4.3/110= 39.09

Therefore preferred value is 47 ohms resistor

How the circuits works

To begin with, the 12V power supply is needed to connect to the red lead (positive) and the black lead (negative) to the circuit as a constant power supply, the LED will not just light up with the 12V power supply there is additional power added to the circuit which is input of 5V to the yellow lead which allows the first LED to light up this happens when the transistor gets the power to close up so it completes the circuit and LED lights up. The same principle is applied to the white lead which allows the second LED to light up. Therefore the user can switch the 5Volts power to yellow lead and to the white LED to allow the light to glow at each time.

Test Procedure

Inorder to test the circuit you must have 12volts power supply and additional 5volts power supply. Both of the negative leads should be connected to the negative input of the circuit. Connect the 5volts wire to the yellow wired input to let the yellow LED light up and you can also use the same 5volts wire to connect to the white input wire which will allow the second LED to light up.

Fault Finding

After making the circuit I connected to 12volts power including my 5volts my first LED did light up whereas my second LED did not light up I checked my components with the volts meter as a result I got to know that my second transistor was a manufacturers faulty good, therefore when I replaced with the new transistor all the components and circuit worked.

Reflection

If I was to re make this injector circuit one thing I would improve is that ill check all my components to ensure that they are working and safe to use.

Experiment No.8

Summary

Vary the base resistor and measure changes in voltage and current for Vce, Vbe, Ic, and Ib. Then plot a load line.

Setup the following circuit on a bread board. Use a 470R for Rc and a BC547 NPN transitor.

Pick five resistors between 2K2 and 1M for Rb. You want a range of resistors that allow you to see Vce when the trnsistor is the saturated switch region and when it is in the active amplifier region. I used 47K, 220k, 330k and 1M, but this can vary depending on your transistor. Some may need to use 2k2. Put one resisitor in place, and measure and record voltage drop across Vce and Vbe. Also measure and record the current for Ic and Ib. Then change the Rb resistor and do all the measurements and record the new readings. Do this for each of the resistor values above.

Your voltage drop measurements across Vce should vary from below 0.3 v ( showing the transistor is in the saturated switch region) to above 2.0v (showing the transsistor is in the active amplifier region) If this is not the case, you may have to try a smaller or bigger resistor at Rb. Talk to your teacher to get a different size resistor, and redo your measurements.

Discuss what happened for Vce during this experiment. What change took place, and what caused the change?

During this experiment the Vce has more volatge gain when ever there is more resistance.

Discuss what happened for Vbe during this experiment. What change took place if any, and what caused the changed?

In this experiment the Vbe is at 0.7V because the transistor only passes the current when it exceeds 0.7V. When the transistor is fully saturated then the Vbe should above the 0.7V.

Discuss what happened for Ib during this experiment. What change took place, and what caused the change?

In this experiment the change is that the current is always very small when crossing the base. Therefore usually the micro amps and since the current is small it is not used for equation.

Discuss what happened for Ic during this experiment. What change took place, and what caused the change?

In this Experiment I have noticed that the bigger the resistor the less current is across the collector.

Plot the points for Ic and Vce on the graph below to create a load line. Plan the values for so you use up the graph space. Use Ic as your vertical value, and Vce as your horizontal value. Using Vbe on the Vce on the Vce scale, plot the values of Ib so the finished graph looks similar to fig 13.

Calculate the Beta (Hfe) of this transistor using the above graph.

At 2590mV B = 1.19/0.01

= 119

At 1420mV B = 3.43/0.01

= 343

At 1066mV B = 4.22/0.01

= 422

Explain what the load line graph is telling you. Discuss the region s of the graph where the transistor is saturated, Cut-off, or in the Active area.

According to the load line which I have constructed shows me that my transistor is in saturated, active and cut-off regions. My readings of Ic is 5.16mA, Vce is 0.609V and Ic is 4.96mA, Vce is 91.6mV these are both located at the suturated region, iilustrating me that these points Ic is very high whereas Vce is low therefore large amount of collector current can flow.

Experiment No. 7

Exercise : Connect the circuit as shown in Fig 12 and switch onthe power supply.

Connect the multimeter between base and emitter.

Note the voltage reading and explain what this reading is indicating.

According to my experiment which I did with voltmeter across base and emitter my reading was 0.802v which is a good reading therefore it means that my transistor is saturated and working well.

Connect the multimeter Between collector and emitter. Note the voltage reading and explain what this reading is indicating.

In this experiment I connected my voltmeter across the collector and the emitter therefore my reading was 53.2mV.

In the plot given below what are the regions indicated by the arrows A & B?

Hows does a transistor work in these regions? Explain in details:

In the region marked A the transistor is fully sturated and works fine whereas the region B is the cut off therefore the transistor is not been sturated and it is not working due to lack of current and voltage.

What is the power dissipated by the transistor at Vce of 3 volts?

Pd = Vce x Ic

= 3v x 12.5mV

= 37.5v

What is the Beta of this transistor at Vce 2,3 & 4volts ?

B= Ib/Ic

Vce 2v = 20/0.8 = 25 is the Beta

Vce 3v = 12.5/0.5 = 25 is the Beta

Vce 4v = 5/0.2 = 25 is the Beta

This indicates and tells me that the Beta is same at all stages of the graph.

Experiment No.6

Meter Check of a Transistor

Identify the legs of your transistor with a multimeter. For identifying and testing purposes, refer to the representation shown above.

Experiment No. 5

The capacitor

The capacitor stores electric charge

Identifying Capacitor "Size"

If thr Farad "size" is not printed on the capacitor, you may find an EIA code listed. Use the table below to figure out the capacitance.

RC Time Delay or "Charging Time"

Capacitors take time to charge. It doesn't happen instantly. The charge time is dependent on the resistor in the circuit and the size of the capacitor. And it is expressed in the equation :

R x C x 5 = T. This is the time it takes to charge up to the applied voltage.

For example, 1,000,000 ohms x 0.000001 F x 5 = 5seconds to charge to applied voltage. This can also be expressed as 1M ohms x mF x 5 = 5 seconds.

Capacitors are often used for timing when events take place. And often the voltage only has to get up to about 2/3 the applied voltage, and this happens about 1/5 the time of their charging. So this is why the 5 is built into the equation. The concept of "time constants"is used here, where whatever the time it takes for a capacitor to built up to the full charge, it takes about 1/5 of that time to build up close to 2/3 of the charge. So you can divide the charge time into 5 segments, and the first time segment is often the time you are interested in.

Practice watching the capacitors charge up the inthe exercise below.

First calculate how much time it would take to charge up the capacitor. Then, connect the circuit as shown above. Measure the time taken by the capacitor to reach the applied voltage on an oscilloscope. Fill in the chart below. Also draw the observed waveforms in the graphs below, filling the details on each one.

The formula for calculating time

T = R x C x 5

0.0001 x 1000 x 5 = 0.5s

0.0001 x 100 x 5 = 0.05s

0.0001 x 470 x 5 = 0.235s

0.0003 x 1000 x 5 = 1.5s

How does changes in the resistor affect the changing time?

As the resistance increase the more time the capacitor takes to charge inorder to reach the maximum capacitance.

How does changes in the capacitor affect the changing time?

The bigger the capacitor is, the more time it will consume to charge up and it will also work for longer period of time compared to smaller capacitor when it is unplugged from the power source.

Experiment No. 4

Exercise : Obtain a breadboard, suitable components from your tutor and build the following circuit.

Vs = 10 & 15volts, R = 1K ohms

Describe what is happening and why you are getting these readings:

The zener diode acts as a voltage regulator and has the output of 5.1 volts even when I vary the voltage from 10 volts to 15 volts. Only the resistor increased in high volts because it comes before the diode.

Experiment No. 3

Exercise : Obtain a breadboard, suitbable components from your tutor and build the following circuit.














What is the value of Vz?
The value of Vz is 5.93V


Vary Vs from 10V to 15V
What is the value of Vz?
The value of Vz at 10V is 4.96volts and at 15V the value is 7.49volts


Explain what is happening here
As you increase the supply voltage the voltage at Vz also increases.


What could this circuit be used for?
It can be used as per 5V1 voltage regulator circuit.


Reverse the polarity of the zener diode.
What is the value of Vz? Make a short comment why you had that reading.
The value of Vz at reverse polarity is 0.9volts.
It is because when I reverse the zener diode it acts as same as the normal silicone diode.