Alternator

On the practical with alternators, we dismantled the alternator and checked to see that all the components are in good working order. First we tested for the winding to ground on the rotor.
I placed the black lead to the centre of the rotor and places the red of the slip ring with the ohmmeter at 2K ohms. It read 1 which is also infinite which is what the specs was. Then tested the winding internal resistance by putting the red and black on the slip ring and the ohmmeter set at 200. The meter read 3.4ohms which is a good pass as it meets the specs. Then we tested the resistance on the stator winding which read 0.4, 0.5 and 0.5 ohms which all met the specs.

Next we tested the positive diodes for the rectifier by placing the common lead on the end of the rectifier and putting the positive the lead on each of the terminals. They read 0.5, 0.5 , 0.5 and 0.6 which all passed the specs. Then tested the same test but with the leads switched around and it all read infinite which also met the specs.
As we dismantled the alternator, we had to check for the bush protrusion length with a vernier caliper. The caliper read 4mm which meets the spec and is good.

Overall, the alternator that we tested was in good condition and all components met the specs.

Stator motor

we first tested the starter on a machine to test and see that the starter is actually functioning before we start dismantling it. The voltage on the starter motor was 11.9V and 58.9 amps. Next we disassembled the starter motor and performed a visual check of the components for any damage, burning physical damage to the coil and poling. The brush on the motor was worn alot. Next we tested the ground test by putting the red lead on the segments of the commutator and black on the armature shaft.The reading was infinity, which is good. Next we tested for the continuity on the armature by placing one probe on the segment and another on another segment. It read 0.2ohms which meets the specs.

Next was to test the diameter and the mica undercut of the commutator with a vernier caliper. My results were 27mm for the diameter and 0.6mm for the undercut. Both met the specs. After that we tested the armature with a 48volt test light, putting the two probes on the segment and it lighted up.

Next we performed a visual check on the field coils and pole shoes and they were all in good shape. Then we tested for continuity in the coils and the grounding. Both met the specifications as they both had 0 ohms when it was not grounded. Now we had to measure the brushes with the vernier caliper. The minimum length was 5mm and my results were 13.94, 16.4, 13.1, 12.8mm so, all were in good shape.

We then tested the solenoid magnetic switch to see the current draw on the component and to check it pulls in when power is supplied and it is held there for atleast 10 seconds. Before reassembling the starter motor, we did a visual check of the pinion gear,brushes and the clutch to check for wear. All were fine.

We reassembled the starter and checked it on the machine to make sure it is working. The no load readings were 11.8V and 46A. The starter is all good.

Relay

relay sues a low amperage circuit to switch on a higher amperage circuit.
we are done by making realy circuit at the class.

There are very common on vehicles and there are many types of relays but they are very similar in how they work. the diagram above is one of the relay procedure on the car..

we were making parallel circuit with 3 bulb and check the voltage drop.
86, is input position so no matter switch is on and off, there will be always 12 volts.
85, when "on"switch opsition, the coil starts consuming the voltage which available voltage dropped as 0volt.
30 is the low amperage but another input position so always 12volts available.

87a. when the switch is off, the switch connect to the 87a so that 12volt goes through here until switch on position.

Diode

In practical for diodes, we first measured the resistance in the diode with the ohmmeter on 2K. Anode to Cathode read 0ohms and Cathode to Anode read 0 ohms.
Then we tested the voltage of the meter probes set on 2K ohms with another meter set on 20V. The meter read 0.6V which is enough voltage to push through the binary layer of the diode. Then we tested the diode for voltage in both direction. From anode to cathode it read 0.52V and from cathode to anode it read 0V. This means it is working good.

We built a circuit with both a diode and a resistor in it and tested the voltage drop across the resistor and the voltage drop across the diode. The resistor had 13.37v drop and the resistor had 0v drop.
Next we tested the amp flow through the diode which was 0.01A and voltage supply was 13.39V.
The voltage drop across the resistor and diode was added together and compared to the supply voltage which was 13.37v.

Now we tried the same experiment with a higher resistance resistor. The voltage drop across the resistor was 12.67v and voltage drop across the diode was 0.6v. Amp flow through the diode was 0.006 amps.
This showed that the more resistance there is, the less amp will go through.

Lastly we created a circuit with a LED instead of a diode. We measured the voltage drop across the resistor which read 11.46V, the current flow through the LED which was 0.001amps and the supply voltage which was 13.39V. This test proved that the LED has less voltage drop because the LED has a light in the component which is a load

It was quiet hard to put together with LED and resistor because we did different from other groups later on we connect the same way as others like connect directly from the battery. if somebody make the circuit then we just look through that, i would feel bored but by thinking and making the circuit, i felt time went so fast that i thank that i didn't miss the class

Resistors

Resistor test.. It was all about calculations, as we read the colour code number....
In oder to read it, we need to know the colour identification. we just can simply check the resistors with multi-meter because that is easier than reading and calculating however by understand this identification, we can just realize the size of the resistor without multi-meter quickly.

Picture above is the colour identification.

band colours	measured value	low tolerance	high tolerance	pass or fail
red red black gold	22.1	20.9	23.1	pass
blue grey yellow gold	686k	646k	714k	pass
brown red brown gold	118.7	114	126	pass
green blue brown gold	552	532	588	pass
orange orange brown gold	326	313.5	346.5	pass
grey red black gold	80.8	77.9	86.1	pass

all measurements are in Ohms units

to calculate total resistance in a series circuit, all you have to do is simply add the resistance within the circuit.

to calculate total resistance in a parallel circuit, you must follow the formula:
1/RT= 1/R1 + 1/R2
we put the 552ohms and 326ohms together in series circuit so that the total resistance is 552+326=879ohms.

And when the two resistors become parallel 1/552 + 1/326 = 1/total resistance which is 204.95

LED test light

LED test light, Actually i mostly liked this class during the weekdays. i love making and fixing something in other word, i love practical especially this LED test. We can buy LED test in the shop but by making ourselves, we will know how it works.

parts list,
brass rod with a sharpened tip and a clean central section half way on the rod which we did the day before.(this will be your sharp probe)

Red LED
Green LED
Black wire 2m long
Red wire 2m long
2 resistors 1Kohms(1000ohms)
Red alligator clip
Black alligator clip
100mm plastic tube 7mm long
pre fluxed solder
shrink tubing:
black 2.4mm diameter about 400mm long
red 6.4mm diameter about 200mm long
black 12.7mm diameter about 150mm long


tool list:
long nose plier
wire cutters
wire strippers
scissors
soldering iron
heat gun
hot glue gun

method:

the LED, resistors and wires need to be soldering together, it helps to have the contacts tinned. solder the resistor to the LED, then the resistor to the wiring, do this for both green and red. cut some black heat shrink, slide it from the wire end to insulate the resistors and led legs (make sure its properly covered).

make sure the brass rod has a nice pointy tip and the middle section is brushed clean (around 10mm), tin the middle 10mm section, then heat shrink the entire rod EXCEPT for the tip (leave a 20mm clearance) and the middle 10mm tinned section.

now before you solder the LED legs to the rod, place a 20mm of the 6.4mm heat shrink through both wires and rod to give extra support. twist the legs of the LED onto the tinned section of the rod, solder the legs onto the rod. make sure its soldered well. to give the LED extra support, hot glue under the LED to the brass rod to give extra support.get the 100mm long 10mm plastic tube, cut a groove on one end, the groove needs to be as long as the two LED is in line, plus 5mm past the LED. slide the support tube from the wire end onto the rod.

now slide a 100mm piece of the 10mm heat shrink over the support tube, slide a 20mm piece of 10mm black heat shrink from the point side of the rod to cover the exposed part of the support tube, then cut 20mm pieces of the 6.4mm heat shrink and cover the ends of the black heat shrink, repeat this process twice for the wire end, you want as much support there as possible. twise the wires and place 15mm of heat shrink every 250mm along the wire, when there is 300mm of wire left, heat shrink it two times then untwist the wires so you have the black and red wire seperated. customise how you like, if you have more than just black heat shrink, go hard!

time to now fit the alligator clips, take out the plastic covers from both clips and place them the right way around on the appropriate wire (red plastic cover for red wire, black for black). strip the ends of the wires about 10mm, twist the wire tightly, insert the wires into the holes on the clips and solder it securely. once the clips have cooled down, slide the plastic covers onto the clip.

if you have followed everything properly, then you will now have a functioning LED test light.
test light is for 24V DC or less
connect the red to the positive of the supply the black to the negative, both led lights will light up. take off the black clip, and touch the point to the negative, the green will go off and the red will brighten. take the red clip off the positive on the supply, reconnect the black to the negative of the supply, touch the point to the positive of the supply and the green brightens.

It almost looks like this. i couldn't take the picture so tried to find same one on internet but only i found is it.

Anyway during making LED test i got a really great time and Fun

Batteries

This week, we worked on a bettery at the workshop. The battery on the car is to supply electrical current to the stator motor which cranks the engine and to all accessories while the engine is off.

There are a number of different batteries, conventional, maintenance free, gel cell, etc, the one we worked on was conventional lead acid batteries.

To understand a lead acid battery better, .there are 6 plates inside of the battery casing when you remove the battery cover, 3 positive and 3 negative are alternated, each set of 6 plates has a charge of 2.1V (volts), 6 sets which total to 12.6V



to inspect the battery, first you must first check the battery specifications, take visual checks, check the electrolyte levels, battery open voltage (OCV) test battery electrolyte specific gravity, high rate discharge test using a load tester. seems like a lot? may be, but it must be done!


lets start with the battery specifications, these are labelled on a sticker on the side of the battery, the battery specs which i got were.
make: Repco
battery number: NS402L
Battery capcity in Cold Cranking Amps (CCA) :310
type of battery: Conventional
Electrolyte accessibility: Yes

Visual check
terminals are tight and clean: No
does the battery show signs of swelling? (caused by over charging): No
Check for corrosion under mounting clamps: No
what areas need attention? terminal corrosion need to be sanded off, electrolyte leakage needs to be cleaned with soda water.

Electrolyte levels
while carrying out this test, make sure you have thick rubber gloves and safety glasses, that no part of your skin is exposed (acid burns is no joke!), that there is a water supply to clean your self if anything should occur.
to check the electrolyte level, you must remove the cell caps and use the srynge to check, they will either be high, ok or low

Our group findings
cell 1ok cell 2ok cell 3ok cell 4ok cell 5ok cell 6ok

OCV test
before taking an OCV test, you must remove the surface charge, you can do this by turning the headlights on for about 1 minute. after that, use a voltage meter set to DC, take a reading over the terminals. set the range on the meter to 20V (unless you have an autoranging meter). i had received a measurement of 12.9V, this is overcharged.

Battery Electrolyte Specific Gravity
to check the electrolyte specific gravity, use the srynge to perform a hydrometer test, write down the readings for each cell and also the colour (clear or murky/white'ish)
our readings were

Cell: cell 1 cell 2 cell 3 cell 4 cell 5 cell 6

reading: 12.25 12.25 12.50 12.50 12.50 12.25

colour: murky murky murky murky murky murky

the specific gravity variation i got from my test is 0.025, which is allowable since the specification of the battery is 25-50

high rate discharge test using a load tester

to do this test, the battery must be atleast 50% charged (12.4V) to be able to supply cranking voltage, if it isn't, charge the battery using a quick charger.

firstly, you must first determine the load current to apply, we have got 155A (1/2 of the CCA of 310)

the specified voltage to be held while load is applied is 9.5V, i had 10.8V

you apply the load for 10 seconds

We also used a Digital Battery Tester. It is a hand-held tool, designed to test lead-acid batteries used in the modern motor vehicle. its ranges include Capacity in cold cranking amps(CCA)'s, Voltage, Temperature in which the tester will operate correctly, Minimum voltage a battery must be able to deliver before a successful test can occur. To check the battery with it, turn the ignition key off, not in the accessories position, then connect the red clip to the positive and black clop to the negative terminals. So then the digital gauge will automatically show up.
The reading shows SAE with 460CCA's. then we move on to the cold test by simply push the cold test button. O.C.V of the battery is 12.86V with 300CCA's which shows pass.