Electrical Questions

[Hoosch]

Electrical idiot here. ops:

Can someone please explain these to me?

Lumens
Color Temperature [K]
Color Rendering Index

I'm trying to pick out the best 96 watt pc bulb. Any suggestions?


Also, I'm trying to hook up canopy fans and would like to have the following explained:

volts vs. amps
AC vs. DC
power supply vs. transformer

Does the power supply that comes with a cell phone also act as a transformer? This is just an example. I'm not actually using a cell phone power supply.

If I have a 12VDC power supply and two 12VDC fans, will I also need a transformer? I'm assuming if I just hook the power supply up to both fans without anything else inline, each fan will only receive 6VDC? How do I figure amerage into this equation? I have one fan that is 12VDC and listed as 0.14amps.

I'm sure this seems extremely basic to all of you.

[m.lemay]

Here s the article you want to read for the lighting questions.http://www.plantedtank.net/forum/viewtopic.php?t=819

volts vs. amps

If you can imagine electricity as being water in a plumbing system then volts would equal water pressure, and amps would equal flow(such as gallons/min). Are you with me so far?

AC vs. DC

AC=alternating current, DC=direct current. AC power comes through in waves which can be seen with an oscilloscope. AC current here in the US comes thru at 60Hz or 60 cycles per second. An easy way to visualize this would be: If you could chart the peaks of The AC waves there would be 60 peaks every second. There would also be 60 valleys per second. DC power comes in straight, no waves. DC is typical of the type of electricity you would get from a battery. AC is typical of the type of power you get in your house outlets.

power supply vs. transformer

Power supply is a generic term meaning: A source of power. A power supply can be a transformer, a battery, the sun, electrical outlet etc....
A transformer is a device that changes the input voltage to a different output voltage usually via magnetic inductance. A ballast for flourescents is a type of transformer. The coil for the ignition system in your car is also a type of transformer.

These are pretty simple explanations to help you to visualize. I hope this helped.

[Buck]

It helped me , Im a pipefitter

[^iMp^]

Can someone please explain these to me?

Lumens
Color Temperature [K]
Color Rendering Index

This link explains everything (I think):

http://www.floridadriftwood.com/lighting.htm

Generally, you don't have to worry about this stuff. If you choose some bulbs that are round 55000K-65000K, you'll be fine. The K rating doesn't matter much except how we (humans) perceive the light.

volts vs. amps
AC vs. DC
power supply vs. transformer

Try these links (or one of the links listed on the link):

http://www.amasci.com/elect/elefaq1.html#aj
http://www.theelectroniccompany.com/converter_faq.asp#2

Very basically, volts are a measure of voltage (electric potential) and amps are a measure of current (charge flow, like through a wire). Simply put, a voltage will cause current and vice-versa. The two are related by Ohm's Law, V=IZ, where Z is some load.

DC is a direct current--like water flowing out of a pipe. Think of the gravitational force as a voltage and the water through the pipe as a current. AC is an alternating current (and thus voltage)--basically, the current/voltage changes with time like a sine wave (or another periodic signal).

A "power supply" simply supplies either a current or voltage (usually voltage). So if you have a 12-volt DC power supply, there are 12 volts DC across its terminals when it is "on". Your wall outlets can be viewed as power supplies. A transformer is used to change (well, not necessarily) a given current/voltage to a current/voltage that a device uses. Your 12v DC fans couldn't simply plug into a house outlet (110V AC @ 60Hz). You'd first have to find an appropriate transformer/converter/whatever.

If I have a 12VDC power supply and two 12VDC fans, will I also need a transformer? I'm assuming if I just hook the power supply up to both fans without anything else inline, each fan will only receive 6VDC? How do I figure amerage into this equation? I have one fan that is 12VDC and listed as 0.14amps.

You won't need a transformer--a transformer is used when converting one voltage/current to another. A 12V power supply will theoretically "always" have 12 volts across its terminals. This 12V power supply can also supply a current. The current that is supplied depends upon the load. For example, if you connect a fan across the power supply, your fan will draw 0.14 amps (current) from the power supply and 12 volts will be across the fan (and power supply). If you place two fans across the power supply terminals ("in parallel" so the removal of one fan will not deactive the other fan) then there will be 12 volts across each fan, but 0.28 amps will be drawn from the power supply--0.14 amps will flow through each fan.

The power supply should have some sort of "max current" rating--as long as its greater than 0.28 amps, you can supply the two fans just fine. Just remember that when devices are connected in parallel, the currents add and the voltages across the devices is equal. When devices are connected in series, the voltage is split (not necessarily evenly) and the current is the same.

Note that I am NOT an electrical expert. I know most of this from a purely academic (and not practical) background.

^iMp^

[^iMp^]

Ack! You beat me to it, Lemay.

I have little experience with transformers, so ignore the stuff I posted about transformers and listen to the moderator.

^iMp^

[m.lemay]

Nothing lost, everything you said just added more detail to what I said.

I just want to clarify one thing about the 12 volt power supply. It is basically a transformer that converts 120 VAC to 12 VDC. IMP is correct in stating that you don't need a transformer in addition to the power supply as the power supply has already done the transforming. The explanation for hooking up the fans is good. Pay particular attention to the part about not exceeding the output Amp ratings of the power supply. I've SMOKED a few transformers in my years :lol:

Marcel

[Hoosch]

Thanks for the explanations guys! That helps a great deal!