Voltage Regulator and LED questions.

Hello EDABoard!

I am new to the field of electronics.

I am just starting out, and i would like to make my own extractor fan, since buying them isn't cheap, and it gives me a basic circuit to build.

I saw someone make one on YouTube, he had 2 12v batteries, a switch and a voltage regulator with 12v output (and of course a 12v fan). Why is the regulator needed? Why not one 12v battery to power the 12v fan? Sorry of this sounds really silly. I've tried googling this information but noone is ever specific.

In regards to the LED, another project I am interested in making that I saw on YouTube; the guy cuts flat SMD LEDS into single pieces, whereas everywhere else on the internet says you can only cut on the dotted line. What's the go here? He was able to solder on tonthe ends of each single flat LED light, but still the internet persists in saying no.

Thank you for taking the time to read my newbie questions! I hope someone has the patience to answer lol.

Hi,

The given "12V" of a battery is nominal voltage.
The real voltage of Pb battery depends mainly on charge status, load current and temperature.
It may vary from 10.5V up to 14.4V.

LEDs.
It makes no sense to cut SMD LEDs in pieces.
Maybe LED stripes.
Where to cu depends on the circuit of the LED stripes. The connection of LEDs in a string, usually with a current limiting resistor.

Klaus

The regulator is probably so the speed remains constant for as long as possible. If you connect a 12V battery to a 12V fan it will run but as the battery discharges, it's voltage will drop and the fan will lose power. Depending on the motor type used in the fan, it will either not try to rotate as fast or it will lose energy and be slowed down by the air drag. The regulator will attempt to keep a steady 12V out so the fan runs at full power until the batteries can't cope any longer. The drawback to the regulator is you lose some voltage across it, you have to put more in than you get out, that is why the two batteries are needed, to give it the extra 'overhead' it needs.

I'm not sure what you mean about the SMD LEDs, I use lots of them but they are always delivered individually or on plastic tape. I always solder to the ends, it's how the manufacturers tell you to do it. I suspect what you are looking at is someone salvaging LEDs from a 'light rope'. If I'm right, you are not seeing the normal way to use them, instead you are seeing an already manufactered device being dismantled to recover the LEDs. 'Light ropes' DO have a specified voltage so cutting them in the wrong place will result in smaller strips of LEDs with indeterminate voltage ratings. If you buy the LEDs from a component supplier you will not have this problem.

Brian.