Archive for August, 2009

When purchasing a car, how do you determine the amount of your down payment and how much monthly payment you can handle?

The best way to determine how much monthly payment you can handle is to complete a monthly budget. Start with the amount of your take home pay and deduct your monthly expenses (fixed, flexible and variable expenses). Don’t forget to include the expenses associated with the new car: gasoline, insurance and maintenance.

Determine the amount of your down payment after you determine how much you want to pay as a monthly payment. Let’s say for example that you want to buy a car that costs $15,000; the special finance rate is 0 percent (for example). After completing your budget, you determine that you want to pay $250 per month for 48 months – this totals $12,000. In light of this, your down payment needs to be $3,000.

There might also be a chance that the financing source is only willing to finance $10,000 of this same vehicle. If such were the case, then, your down payment would increase to $5,000.

History & Principles of Cars Alternator

Electricity is produced by moving coils of wire through a magnetic field, thus producing a current flow in
the coils of wire. Two different devices have been used on cars to produce electricity: Generators and
Alternators.

Early GM cars, up through 1962, used a Generator to produce electricity. Generators, for those of you too  young to have seen one, are about the size, weight and shape of a GM starter. They use permanent magnets  to produce Direct Current (DC). The magnets are located stationary around the case, and the currentproducing  coils are spun on a shaft in the center of the generator. Generators are neat in that they do not  need any external source of power (a battery) to begin producing electricity: all you have to do is to spin  them, and they produce a DC output. But they are heavy, and they do not produce much output at low rpm:  you’ll typically see the headlights on older cars with generators go noticeably dim at idle.

In 1963, GM introduced Alternators on its cars. Alternators do not have permanent magnets, but rather  send a small current through a series of coils to produce an electrically-induced magnetic field. In an  alternator, the magnetic field is created by spinning the electrically-induced magnetic field in the center of  the alternator, producing current in the stationary, case-mounted coil. This makes an alternator much  smaller and lighter, and its output at low rpm can be maintained by increasing the strength of the magnetic  field. An alternator, however, does not produce DC output: Due to its design, an alternator, as the name  implies, produces Alternating Current (AC). This AC must be changed to DC before it can be utilized in an automotive electrical system.

Alternating current, if visualized, is like a wave moving up and down: it cycles from positive to negative.  It the mid point between positive and negative, there is no current flow at all. Obviously, then, if we only had a single coil producing AC power at low rpm, this cycling and “dead spot” would make our lights and electrical system blink on and off very quickly. Not good for our application. An alternator, then, typically has three separate coils, each producing its own “wave.” These waves are set as far opposite each other aspossible, so by the time they “overlap,” they are producing a steady stream of AC power. But now we must convert it to DC.

Each of the three current producing coils is attached to two diodes. A diode is an electrical component that  allows current to flow one way, but not the other. It’s like a one-way door. One of the “one-way doors” is set to “open” in one direction, while the other one “opens” in the opposite direction. Thus, when the alternating current is flowing in the “positive” direction, the positive output is shuttled out of the one diode.

When the current shifts to the “negative” direction, it is allowed to go only out of the other diode. Thus we have separated out the two elements of the alternating current into a positive and negative DC power output. With all three of the coils doing this at staggered times, a steady stream of DC power is realized.

Pretty simply, huh?

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