Sir/madm . Using 7805 , i want to make my own varaible voltage .ie. 3vdc,6vdc and 12 vdc. so in this case , how do I calculate value of resistor for 3vdc, value of resistor for 6vdc and value of reistor for 12vdc. Please help me here
thank you

 

You really can't make a proper 3 volt regulator using the 7805 and resistors.

An LM317 would be better and go even lower than 3 volts.

 

I have too much time that I need to waste today.

 

Can I buy some extra time from u ??

EDIT : Yard Work

 

I have too much time that I need to waste today.

Is that for real? That's all there is to it?

 

Is that for real? That's all there is to it?

Maybe

The thing is, learning what the available components can do.

Years ago It wasn't (quite) as tough.

Now, it's a bit mind-boggling (In my opinion)

But, I still appreciate stuff that glows

 

But, I still appreciate stuff that glows

Wish I could get to that point! I seem to have got hooked on the smoke.

 

Can I buy some extra time from u ??

Sorry. Already stuck with yard work. Finished a plumbing job at 5 pm. Have to wait until 7:30 pm when the heat index goes down to 93 degrees so I can mow the lawn. (Mowing sucks in August in Florida!)

 

Wish I could get to that point! I seem to have got hooked on the smoke.

A little smoke, once in a while is a good thing ...

 

Sorry. Already stuck with yard work. Finished a plumbing job at 5 pm. Have to wait until 7:30 pm when the heat index goes down to 93 degrees so I can mow the lawn. (Mowing sucks in August in Florida!)

How in the heck can you STAND plumbing !%$#@$#^%# ???

I have boxes of plumbing pieces that don't fit what I need at the moment.

EDIT: I HAVE plumbing stories .......

 

How in the heck can you STAND plumbing !%$#@$#^%# ???

It comes with the territory, but among things I don't like to do, from worst to less worst, the list goes:

Painting
Plumbing
and gets better from there.
There's nothing quite like laying in a puddle of poop water, trying to fix ruined metal, while the mosquitoes try to eat you alive...and yet, I hate painting even worse.

 

#12,

Does it still rain every afternoon in Florida ??

 

I hate painting more than anything............

But, what about the ghekos ?? (small lizards how do you spell that ??)

 

#12,

Does it still rain every afternoon in Florida ??

It has this week.

 

I hate painting more than anything............

But, what about the ghekos ?? (small lizards how do you spell that ??)

The native lizard is the anole. Geckos (insurance sales lizards) are very rare here.

http://en.wikipedia.org/wiki/Brown_Anole

 

...and yet, I hate painting even worse.

Gosh, I enjoy the actual painting. Getting ready to paint - scraping, sanding, chiseling, repairing, cleaning, and on and on - would be considered cruel and unusual punishment if you forced prisoners to do it. Painting goes so quickly and makes such a big difference.

 

Gosh, I enjoy the actual painting. Getting ready to paint - scraping, sanding, chiseling, repairing, cleaning, and on and on - would be considered cruel and unusual punishment if you forced prisoners to do it. Painting goes so quickly and makes such a big difference.

I quite agree. Painting is like soldering: 90% of the work is preparation.
The difference is that if painting takes 4 to 6 hours, the preparation time was 40 to 60 hours. Soldering a pipe takes about 50 seconds, so the preparation takes about 8 minutes.

 

Thanks for valuable suggestion made by tubeguy. I have gone through the circuit diagrame for LM317. But here, i wan to know how the value of resistor is calulated. And also, from where did we get 1.25 volt.Please kindly explain for me.

Thank you all

 

thanks for the diagrame of LM317. Please kindly explain me how the value of resistors are calculated.
Thanks you somuch

 

1.25 volts comes from the data sheet for the LM317 chip.
The value of the resistors is calculated by using the formula I wrote on the drawing or by using the formula on the data sheet for the LM317 chip.