Logic probe construction.

For a probe construction we needed a couple of things like :
Brass rod 150 mm long.                                   Red LED.
Green LED.                                                     Black/Red wire 2 meters.
2 resistors 1KΩ                                               Red/Black Alligator clips.
100mm plastic tube 7mm.                                Shrink tubes.

 Her i have soldered a 1KΩ resistor to a red LED, and a black wire, the soldring cant be to bulky or rough as it will rip the shrink tube that we use to cover it all up with.

 Here i'm soldering the second resistor to a green LED.

now we just slide the shrink tube over the resistor and the soldring, and by using a heat gun we can apply enough heat for the shrink tube to shrink and wrap tightly around the wire.We do this again for the green LED.

 this just a photo of how i tied up the resistor with the wire and was ready to solder.

 as you can see the soldering had to be very neat.

 And this is what it looked like after we soldered the green LED and red LED on and put some shrink tube around the wire by using the heat gun again we just applied heat to the tube and it shrinked,

 this just the red LED ready now we were ready to put the plastic tube the LEDs but after we connected them to the brass rod, with a little soldering.

and we placed some shrink tubing ove the brass rod as we so it doesnt short with and wire, after this slided the plastic tube over the LEDs and with the sharp end of the brass rod out, we used hot glue to keep the LEDs stuck to the plastic tube. after that you just twist the wires up nice and neat, and jus place some heat shrink tube over the probe and apply heat to make everthing nice and tight so nothing goes lose and we'r done.You just add alligator clips to the end off the red and black wire with a little solder so the wire stays in place with the clip and you have finshed making a probe,



The probe tester we made is only for 24volts or less. but DC volts only, you just connect the postive aligater clip to the positive side of whatever your testing for example a battery and the black to negative. both the LED lights should glow green and red, and when to touch the brass front end of the tester to positive the green LED will go out and red LED will get brighter because now thier is postive on both end of the green LED, and since the voltage isnt been slip between red and green LED the red LED has got brighter.but when you connect the probe to negative, the same thing will happen but wit the green LED getting brighter and red LED will go out,

Alternator

The alternator is used to charge the battery,when the car is running, its kinda like a generator,the alternator supplies electrical  energy to the electrical system when the engine is running.Also it compensates for the changing electrical load on the cars battery or electrical system while the engine is running.

This is how i put what i learnt in theory into partical, by doing a test on the alternator,regulator and testing the diodes on the rectifier.

 this is how i took off the cover for the alternator, i had to remove the nut on B terminal and the insulator.

                               now i'm just removing the three nuts that hold the back cover,

 this is what it looked like after the back cover off, you can now see the rectifier and the voltage regulator.

 this is after the voltage regulator was off , here you can see the brushes which supply electricity to the slip ring.if they are to short the brush springs cant apply enough pressure to maintain constant contact.

                            now i was ready to take the rectifier off.and test the positive and negative diodes.

                                                           this is the rectifier that i took off.

                     this is the stator winding, and i did a resistance test, and also a ground test.

this is what the alternator looked like with the rectifier off.

                                        this is when i was doing the test on the positive and negative diodes

now i was ready and finshed with all the tests and ready to put the alternator back together,

                                      


Over all the alternator failed the test due to the regulator, it had a reading of 14.6 on the voltage test. But the spec was 14.4 so thats why it failed.

Circuits

i learnt that a fuse should be 20% higher then the current flowing through it, for example 10volts should have a 12v fuse, and also that in a series circuit if one blub fuses the whole circuit will fail because the current cant flow through, but in a parrel ciruit it doesnt matter due to the fact the blubs are connect by two differnt wires


In partical we made our own circuits using a circuit board and a power source, i learnt the reason why if a bulb fuses in a series circuit the whole circuit fails, that because there is only one voltage supply to the circuit, therefore voltage must pass through all the consumers, and if one fails they all fail, all the resitance does'nt have to be the same.But in a parrel circuit if one consumer fails, the other one stil goes because the current flow splits, to go to the diffrent resistance, so if one fails the other one stil goes.i learnt that to do calculations in compound circuit always find out the total resistance of the parrel area first.




　
Here are some circuits:

Car Battery

12/4/2011, We started learning about car batteries and how they work, why they work the way they do and what are the dangers of a battery. i think we all have thought about what will happen if we connect negative to postive and positive to negative, will the battery blow up ?. i've learnt it may blow up or it will blow the fuse, but its not the best test you will wana do, because a car battery is 34% sulphuric acid and 66% distilled water and is knowen as electrolyte. cloths and acid dont go very well together neither does skin and acid,So car battery is quite dangerous if we dont respect the manner its made to be used in.everyone thinks a car battery stores electricity but it stores chemical which produce electrons.when the car is not started the battery keeps the car computors alive and keeping the memory alive.sometime the battery might be to small or old and it wont be able to do everything its made to do,thier are two types of batteries one is a primary cell, its a everyday use battery exmaple the one you use in torchs and stuff and it can not be recharged once its discharged, but the car batteries are secondary cells which can be recharged once thier are discharged,Batteries have vent caps to let the gas out because batteries cause hydrogen,when a battery is discharged the water level inside the battery raises and the acid level drops, But when the battery is charged again the acid level raises and the water level drops.

COLD CRANKING AMPS AND CRANKING AMPS,

Cold cranking amps is the ability of a battery to deliver a specified current at -18.c for 30 seconds without voltage of each cell  of the battery falling below 1.2volts.

RESERVE CAPACITY,

Is the time in minutes a fully charged battery will supply a constant load of 25 amps, without the voltage falling below 10.5volts,

AMPERE HOUR (A/H)

Is the amount of current a fully charged battery can deliver for 20 hours without the battery voltage falling below 10.5volts.