LED Test Light

   Howdy folks! We're back again with TTEC 4841-Easy Car Electrical. I'm Tommy Alpa Shepard aka Tung Nguyen will bring you an easy insight of a device which handles, without wasting over 30 bucks at an electrical store and probably would damage your circuit. Yes, it is the logic probe LED tester. Even though this is an individual practical assessment, before that, BIG THANKS to my classmate Umar for helping me familiarize with soldering- one of the central skills needed to successfully pull this off.
   ITS THE LOGIC PROBE and the logic is simple: All constructions are shown in this wiring diagram as a both general and detailed idea shaping: 

  Though all instructions were provided during this assessment but there are some points I'd like to emphasize. During construction using this diagram as an instructor, you need to be clear about 4 things:
1. Where to put components, orders .etc.
2. Where need soldering.
3. Where need insulated.
4. Last but not least, know how the electricity will flow in all situation.
  Order is very important. You might as well put the diodes LED the wrong way just because the long lead of Green which supposed to be soldered to the rod were hooked up with the resistor, and then you continued to follow everything else in perfect order. In the end you tested it and pissed off and wondered why the F*** it didn't work. Well, that's why. I guess you know what I mean.
  One thing I realize about this is knowing how the current flows is the second most important rule that saves your ass when things go whacky. Instruction says Green is for positive, Red is NEG. But if we take a closer look, we will definitely see why it is called LOGIC PROBE. Let say you make a mistake hook the long Red into the brass and its short soldered to the R2 resistor. Don't panic because you just make your Red a positive indicator, so why the hell cry while you can make the rest into a negative indicator. Whatever you do, no matter how big your mess is when start, just remember to check it before too late, and for your sakes please remember these are just diode LEDs, so make use of their nature.
   OK! Back to some educational interpretation. I'm going to explain how this works. As there are 3 remarkable terminal in the whole circuit: Red Alligator clip positive; Black Alligator Negative; and the brass rod is a free terminal or it can be referred to as a ground. There are also 3 main situations at which this Logic Probe will operate also 3 main ways that we have to test our probe:
1. Positive-Negative
This is when we connect the red alligator to positive of a 12V battery, and black alligator to battery negative. And the whole thing works just like a basic series circuit:

From positive - Resistor R1 - Green LED diode - through rod - Red LED diode - Resistor R2 - Negative
This means both LEDs will light up equally. There is no current flowing till any end of the rod because it is not grounded. If the rod is grounded when Pos-Neg is happening then we've got a short circuit.

2. Positive- Ground
Red Alligator to battery positive; rod touched with battery negative. The current will flow like this:

Electricity finds it easier to go through the end of the rod to ground, after doing its job brightening up the Green LED. This is why the Red LED doesn't go on, because flow doesn't even bother to go through the Red LED and then has to go though the very tough R2 1 k Ohm resistor in order to get to ground. Plus, the black alligator is on air.

3. Ground- Negative ( or Free Terminal- Negative)

 The rod is touched to battery positive, the black alligator is clipped with the battery negative. The current only flows through the Red LED to ground. The Red Alligator is on air, plus it is a diode, current can not flow back.

  So in the end, we know the theory, we know how to make it, we know how to test it, we know how it works. We are all the way up to using it in the future as a reliable tool for back probing- checking sensors, battery.etc..

I built some circuits last week, simple ones

    Introduction: This is how we wire an individual circuit; a series circuit; a parallel circuit; and a compound circuit. Any interpretation following is purely my understanding of what is really going on in any of those circuit. Big THANKS to bigmitch, for opening my eyes about electricity. Here we go.

    We all know the drill: get a circuit board; enough wires; a multimeter. First of all check the probes for resistance, then check the supply for 12V, check if we got fuses installed( if we run out of fuses because we accidently short our circuit; we'll have to direct it, and make it right, and hopefully we won't blow anything on the wall). All done? Now lets get into the circuits.

   1.INDIVIDUAL CIRCUIT
Nothing special here really: Pos+; fuse; switch; bulb; Ne-. The key thing is  we try one with big bulb and then with small bulb. We were assigned to identify the change in current measure in the circuit if the resistance change: Small bulb-0.33A; Big bulb-0.72A. This explain that the small bulb lights less because it has greater resistance, which cause the current to be lesser hence smaller wattage than the big bulb.



   2. SERIES CIRCUIT.

    This is the difference between series and individual: the current change. In series, the current runs through any part of the circuit is the same. But voltage shares, V=IxR, therefore, the smaller bulb will draws more voltage. If u have 2, or 3 identical bulbs, voltages are the same for all. If u have a series of different bulbs, the bulbs with most resistance with draw the most voltage, and then same goes for the 2nd largest, 3rd largest.
    But also in series circuit, the more bulbs you add, the more the total resistance increases( Rt=R1+R2+R3+...+Rn), hence the more the total current decreases, and the result is dimmer for every additional light bulb as well as all light bulbs.
   3. PARALLEL CIRCUIT.

   We built a parallel circuit with 2 bulbs, and then we measured available voltage at each light bulbs, we got approx~ 12V for both. Also; voltage drops across each bulb is 12V. This indicates that the voltage rule for parallel applies here. Force from the supply is endless and there's no stopping when it has 2 ways to push. For the Amps readings, we got 0.73 for each bulb and supply current of 1.46. This means that currents from + travels to junction then splits up 2 ways distributing to each bulb, and then they come back and add up again, as Kirchoff Law states: Total I in= Total I out.
   In parallel circuit, the brightness of each bulb is maintained since each branch is an individual circuit. And because AV is preserved for each, the branch current is also maintained by only being affected by its own bulb resistance, therefore, the brightness is maintained.

  4.COMPOUND CIRCUIT.

This is when all the fun kicks in. We were supposed to wire 2 parallels and 1 series following, and all 3 are big bulbs. But somehow, the two parallels didn't light up as they supposed to, only the series bulb. So we decided to wire the 2 parallels using small bulbs, here is the result:

  Available Voltages(AV) through both bulbs are both 12.6V, and after are both 5.25V(approx~). This tells us that VD across both bulbs are about 7.35V, so 7.35V is comsumed by the parallel circuit, only 5.25V left for the big bulb. Why? Because small bulb has higher resistance(approx~ tripled the R of the big bulb), therefor the whole parallel compound's resistance is just happened to be larger than the big bulb stands alone, hence draws more voltage.

5.REALIZATION

   U see parallel is way better than series circuit because of no matter how many light bulbs you wire there, the voltage across each one of them is the same, the more you wire, the less total resistance you have. And the cool thing is the current doesn't drop for any additional bulb installed.
   In the experimental compound circuit we tried, we add one more bulb in series:



We can see clearly how a parallel brightness is worsened by adding series. More bulbs means more resistance as the total current drops, the voltage through each bulb also drops, leading to overall downfall of brightness.
So in conclusion, series circuit of consumers is not an effective way for optimal operation, but parallel. A series circuit in series to a parallel circuit sabotages the normal operation of consumers component in the whole circuit.
Because of its nature, parallel circuit is the main circuit for bits and pieces on your car. Multiple lights, countless switches,.etc..ưhich can only be met by parallel circuits. 

Electrical Circuit rules

In series, only series, the bulb with greatest resistance will draw all the available voltage to use first.

Electrons/ atom: conductors like metal has lots of "free" electrons.

Potential difference is the voltage diff between + and -: E.G: +=12.6; -= 0 => Po. Diff.= 12.6

Individual circuit: Fuse: restrict Amp; bigger the Amp; hotter the heat. As there is no fuse , the 2 big amp will heat up the wire on fire
Short Circuit: wire doesn't go through the bulb(resistance) but shorted 2 earth, will return to Ne- => this will nmaintain a super big Amp n will burn the insultator and set fire.
E.G battery charger broken wire n stuck 2 wire 2gether will get a big shorted circuit

Remember how to check 4 a shorrt circuit.

Variable resistance: use 2 control the Amps.

I: Impedance


WIRE SIZE: Resistance= length * diameter.
Long wire; narrow diameter= high resistance.

1st post safety

First lesson on electrical, read through all the safety notes; car jack needs 2 be concerned; 1st thing before using a fire exstinguisher; check if its the right one 4 the case: 4 example: electrical fire: use CO2 gas exstinguisher. Ed May book needs 2 be returned by 15th April.