# DIY +3v/1A Regulator Circuit

Discussion in 'The Projects Forum' started by george0039, Jan 30, 2014.

1. ### george0039 Thread Starter Active Member

Oct 15, 2008
126
5
Hello

I was wondering if anyone here knows of a DIY +3volt, 1A output circuit? I have made regulator circuits with the LM7805 and the LM7806 BUT I was asked by a R.C boat club member if one in +3volts exists, it would be connected to the main battery: 12v upto 24v.

I tried ebay and No Luck for the Transistor. This circuit has to be small because of limited boat hull space. I was hoping it would be like the LM7805 regulator transistor with a few caps and a heat sink and leads.

Thanks for looking here and your help.
George

Nov 12, 2008
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3. ### george0039 Thread Starter Active Member

Oct 15, 2008
126
5
Hi ronv

Thanks for the link. Question, what about if the I/P volt. is 12v, is there a volt. reg. trans. that would give me 3v out and 1A?

George

4. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
1,066
The power dissipation (heating) of a linear regulator is (Vin-Vreg)* I, so for 12V in, you will be dissipating (12-3) * 1 = 9W, which is a lot of heat (large heatsink or water cooling required . it is a boat, isn't it), and a lot of wasted power from your batteries...

LM317 can be set up for any output voltage from 1.25V on up. Get the one in the TO-220 package.

5. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
If you use the 317 from a 12V input, you can also add a power resistor n series to burn some power but that's a pretty mickey mouse design. It is the cheapest way to go by far.

6. ### GopherT AAC Fanatic!

Nov 23, 2012
6,061
3,830
Go get the eBay part listed above. Little power is lost vs the lm317 and all you have to do is solder some wire, turn the screw PM the blue potentiometer to get the voltage you want and put it in a project box from RadioShack (or eBay)

7. ### george0039 Thread Starter Active Member

Oct 15, 2008
126
5
Hi gopherT

What do you mean by "PM the blue potentiometer"? Glue it in place when the desired output voltage is reached after adjustment?

George

Can that board also be used without it`s project box, just have it encased in silicon or epoxy for water proofing?

8. ### GopherT AAC Fanatic!

Nov 23, 2012
6,061
3,830
I meant, "PM" means "on". My thumb missed the "o" and hit the "p", the super-smart iPad gets credit for the rest.

By all means, put it in what ever case you want. Just be careful with silicone bricks, it is like putting a wool blanket around it so it cannot dissipate heat if you have a linear regulator (see option below).

You can also set it for 5 volts and use an LM317 circuit to get to the final voltage. The benefit there, there is not big heat issue or energy loss issue as you drop voltage with a switcher voltage regulator. Then, small voltage drop from 5 to your target of 3 is almost nothing for heat issues.

Linear regulators give cleaner power, less noise.

9. ### #12 Expert

Nov 30, 2010
16,337
6,820
If you can get a physically small, switching pre-regulator (24V to 5 V) then Gopher is right. 21 watts would need so much heat sink that a switcher could be smaller than just the heat sink for an analog regulator.

10. ### george0039 Thread Starter Active Member

Oct 15, 2008
126
5
Hello Again

I have taken gopherT `s advice and ordered the ebay one.

George

11. ### bountyhunter Well-Known Member

Sep 7, 2009
2,498
507
Hard to beat what you can get on ebay these days.