SpudFiles

Lentamentalisk wrote:think of it like this:
the power plant sends out its electricity, at bazillions of times the voltage and watage that comes out your wall. the electricity does not instantly turn the first house it comes to into a gigantic fireball, the house takes what it needs, and then the rest continues on to the next house, otherwise we would all need our own power plant, and that would just not be economically possible...

Erm, no, that is not how it works.... There is a transformer for each group of houses, otherwise it would probably burst into a fireball.

OK so is the diagram that jimmy101 posted right or wrong?

wangpushups wrote:OK so is the diagram that jimmy101 posted right or wrong?

It will work just fine.

I can tell you, from experience, that Jimmy's circuit will work perfectly fine.

just don't go trying to wire different LEDs in parallel cause only the one or ones with the lowest resistance will light up, the only way to wire LEDs in parallel is to put a resistor on each!

ammosmoke wrote:

Lentamentalisk wrote:think of it like this:
the power plant sends out its electricity, at bazillions of times the voltage and watage that comes out your wall. the electricity does not instantly turn the first house it comes to into a gigantic fireball, the house takes what it needs, and then the rest continues on to the next house, otherwise we would all need our own power plant, and that would just not be economically possible...

Erm, no, that is not how it works.... There is a transformer for each group of houses, otherwise it would probably burst into a fireball.

Erm, no, that isn't how it works either. There are step down transformers between the high tension (=high voltage) lines and the standard 120V used in a US home but they really only swap voltage for current. The total power entering the house is still typically 24KW (200A at 120V). So, even with the stepdown transformers there is enough power in the house to turn the typical appliance into a fireball, if that was how electrical devices used power.

Most simple devices (light bulbs, heaters etc.) self limit the amount of power they will draw. So even though there is 24KW available to the typical 100W light bulb it will only draw 100W. (If it did draw 24KW the circuit breaker would trip.) Some devices are not self limiting. In general, semiconductors will not properly self limit their power useage. That is why a LED fries itself if hooked to a power source that isn't current regulated. More complex decices like a TV are current limited by their own internal stepdown transformer and power supplies.

All devices in the typical home are wired in parallel and self limit the amount of power they draw.

wangpushups wrote:

Yep, exactly correct. Just remember that LEDs are polarized devices, they have a "+" and "-" contact (unlike an incandescent bulb). If the LED doesn't light up then you have it wired backwards.

If the LED is too dim, use a smaller value resistor to make it brighter. If the LED is too bright, and is getting hot to the touch, you'll need a larger resistor to keep from cooking it.

In the LED circuit it doesn't matter if the LED or the resistor is first in the circuit. Either way will work.

Depending on the type of fan you are using the fan may also be polarized. Generic DC motors will operate with the voltage supplied in either direction but the direction the fan rotates will change. CPU fans (and most other brushless fans) will only operate with the correct polarity.

they are polarised because they have a circuit inside that is a brushless motor controller for the fan because the motor actually requires at least two AC sources that are out of phase with each other.