LED lowers Voltage

[kaspar389]

I dont know what you just said. Can you explain it more...simply lol.

I only understand I need a 120 ohm resistor. Can someone explain this whole resistor thing, and what it does to everything, and what it does to the britness of the LED. DO I hook up the resistor to the - or+ of the LED, is there a + or - on the resistor?

Sorry for asking questions, I just...want to know.

 

[audioguru]

The resistor in series with the LED limits its current. Its max allowed current is about 30mA. It is a very old LED so it isn't very bright at 30mA. At less current then it is less bright. A higher resistor value reduces its current.

The 9V battery does not have much capacity. Its voltage drops as it quickly runs down. The 5V regulator needs a minimum input of 7V so measure the battery voltage frequently and replace it frequently.Six AA cells in series have 5 times more capacity and cost about the same as a 9V battery.

 

[kaspar389]

The resistor in series with the LED limits its current. Its max allowed current is about 30mA. It is a very old LED so it isn't very bright at 30mA. At less current then it is less bright. A higher resistor value reduces its current.

The 9V battery does not have much capacity. Its voltage drops as it quickly runs down. The 5V regulator needs a minimum input of 7V so measure the battery voltage frequently and replace it frequently.Six AA cells in series have 5 times more capacity and cost about the same as a 9V battery.

You lost me at the ciruit drawning.

How do I hook up the 120ohm resistor.

And, I would get 6 AA, but I cant fit that into a portable altoids tin.

 

[kaspar389]

What kind of a resistor would I need if I got 8 AA batterys? Or 6AA batterys.

 

[audioguru]

You lost me at the ciruit drawning.

My circuit is drowning? My drawing? It shows all the parts that are needed, their values and what connects to what.

How do I hook up the 120ohm resistor.

My drawing shows one end of the resistor is connected to +5V and the other end is connectd to the anode of the LED. Solder them together.

What kind of a resistor would I need if I got 8 AA batterys?

8 alkaline battery cells make 12V when new. Most is wasted to make only 5V. The LED and its same resistor are connected to 5V the same as before.

What kind of a resistor would I need if I got 6 AAA batteries?

6 alkaline battery cells make 9V when new, the same as a 9V battery except their capacity is double. The LED and its same resistor are connected to 5V the same as before.

 

[kaspar389]

Does the resistor have a + or a - side? Which side is the anode? The long or short one.

 

[kaspar389]

Why do you have the .01 UF and the 100 UF in there?

 

[audioguru]

Does the resistor have a + or a - side?

No. A resistor is not polarized. Both ends are the same.

Which side is the anode? The long or short one.

The short wire on an LED is its cathode. The rim of its case has a flat part near it.

Why do you have the .01 UF and the 100 UF in there?

My drawing doesn't have a 0.01uF capacitor.
Regulator manufacturers recommend an input capacitor of about 0.22uF and an output capacitor of 0.1uF. For some circuits a 10uF output capacitor is best.
I increased the value of the input capacitor to 100uF because a little 9V battery is weak and the 100uF filters it well.

 

[kaspar389]

In your drawing you have a 100 uf, then a .1 uf, then a 120 resistor.

So, let me get this straight, I just need to connect the 120 resistor to the + of the LED(the long one)

 

[audioguru]

I just need to connect the 120 resistor to the + of the LED (the long one)?

Yes, you are correct.

 

[kaspar389]

Yes, you are correct.

So, I dont need all those other resistors( the .1 and the 100uf)

 

[audioguru]

So, I dont need all those other resistors( the .1 and the 100uf)?

They aren't resistors, they are capacitors.
The manufacurer recommends them and all circuits have them. Yours should also have them.

 

[kaspar389]

Could I use 2 nine volt batterys and get a better charge?

 

[audioguru]

Two 9V batteries in parallel have double the capacity of one battery. So they will last twice as long.

What are you charging?

 

[kaspar389]

Im trying to charge a ipod.

Cause, the last person said that 9v wont charge anything. I read online that 7 or 6 AAA or AA will charge a ipod, so I was wondering mabye two 9v will to.

 

[audioguru]

There are many ipods. One has a tiny battery and another has a pretty big battery. I don't know which battery yours has. What is the output rating of its charger and how long does it take to charge?

 

[kaspar389]

Well, every IPOD charges with the same cable, its just a USB cable which is 5volts.


But, either way Im charging a ipod nano. The old vers\ion

 

[audioguru]

There are a few 'MinyBoost" ipod chargers or extra battery circuits on the internet. One says it doesn't work. Most are "instructables" with no schematic or errors on their schematic.

The best ones use 4 AA Ni-MH rechargeable cells that last a long time and don't need a voltage regulator (4.8V to 5.0V).

 

[kaspar389]

!! I got the 100ohm and 2 10ohm resitors(RS didnt have 120ohms) so now it works. I just used a 9v. It should be fine..cause, I didnt want to have a big box, i wanted it portable.

Thanks for the help

 

[audioguru]

The resistor in series with the LED limits its current and adjusts its brightness.
120 ohms makes it very bright.
150 to 220 ohms makes it not so bright.
270 to 1000 ohms makes it dimmer.
1.5k to 10k ohms makes it very dim.
15k to 100k ohms makes it extremely dim.