# how can i convert 24v to 12v?

Discussion in 'General Electronics Chat' started by CornyCorn, Feb 13, 2016.

1. ### CornyCorn Thread Starter New Member

Feb 13, 2016
12
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Hello, this is my first post so please bear with me.
I am 12 years old and i am working on a prototype for an invention i have. I will need to turn 24vdc into 12vdc, but i want to use something that:
-will not generate heat
-that is small in size (about an inch)

Thanks!

2. ### panic mode Senior Member

Oct 10, 2011
1,329
305
you can make voltage divider using two same value resistors. but you will quickly find drawbacks to this if you need significant current. in that case switching regulator is what you need.

3. ### ScottWang Moderator

Aug 23, 2012
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777
How much current does the 12V needed?
The size is 1 inch=2.54cm?
If just a light current then you can using one resistor and one 12V zener or LM2576-12V 3A, LM2596-12V 3A.

CornyCorn likes this.
4. ### dl324 Distinguished Member

Mar 30, 2015
3,379
651
Welcome to AAC!
Don't want to discourage you, but what you want to do is not possible. Even the most efficient regulator will generate heat.

5. ### Lestraveled Well-Known Member

May 19, 2014
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Perhaps you are being too critical. He is 12 years old and not a crusty old fart like you.

@CornyCorn What is your definition of "will not generate heat"?

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6. ### CornyCorn Thread Starter New Member

Feb 13, 2016
12
1
I apologize for being vague. i already have a transformer to 24v. I need to step down 24 volts to 12, power a few components, and then step it down to 5 to power some more components.
Also should I have the voltage stepped down to 12v then 5v or should I have 24v stepped down to 5v then stepped up to 12?

Thanks

7. ### hp1729 Well-Known Member

Nov 23, 2015
2,099
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24 Volts, 12 Volts and 5 Volts at how much current. Power (E x I) will determine the method you use to a big extent..

8. ### dl324 Distinguished Member

Mar 30, 2015
3,379
651
If you specify your current requirement(s), you'll get more appropriate suggestions.

9. ### Alec_t AAC Fanatic!

Sep 17, 2013
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1,136
If you don't know the current requirements, at least tell us what the 'few components' are that you will be powering at 12V and at 5V.
Incidentally, 1" is just one dimension. What are the other dimensions?

10. ### Evanguy Member

Dec 21, 2014
81
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A simple buck converter should work for you. there are some circuits on google or they can be had on ebay for about 2\$ i assume you will be drawing less then a few amps. some even with led screens to show output as they can be varied

Mark Colan likes this.
11. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,155
772
Lm7812, Lm7805, Lm2596, Lm317, all of these regulators will work, but until you give your current limit, we just keep guessing.

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12. ### AnalogKid Distinguished Member

Aug 1, 2013
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1,299
Where are you located, and what is the general nature of your invention?

ak

13. ### CornyCorn Thread Starter New Member

Feb 13, 2016
12
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The current draw will be around 1-2 amps.

14. ### CornyCorn Thread Starter New Member

Feb 13, 2016
12
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Are there any models that you recommend? I prefer to have ones with PCB pins.

Last edited: Feb 14, 2016
15. ### hp1729 Well-Known Member

Nov 23, 2015
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7812 for 12 V. Same circuit but 7805 for 5 V. Actually only the regulator is needed. The caps and stuff are not mandatory, depending on the rest of the circuit. Even with a small heat sink you are looking at about one cubic inch.

16. ### GopherT AAC Fanatic!

Nov 23, 2012
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He said no (little) heat. Now you recommend a part that works as a voltage regulator by purposely converting the excess (VxI) as heat? That poor little 7812 will dissipate 24-12volts of voltage drop = 12V and then 12V x 2 amps = 24 watts of heat. Try again.

17. ### dl324 Distinguished Member

Mar 30, 2015
3,379
651
A 5V linear regulator would dissipate P = IV = 2A*19V = 38W. You should use a buck (step down switching) regulator to minimize power dissipation.

They sell switching regulators that are drop-in replacements (PCB hole pattern only) for LM78xx regulators, but they're relatively expensive and probably won't handle more than 1A.

18. ### ScottWang Moderator

Aug 23, 2012
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Did you see the current he needed -- around 1-2 amps?

19. ### hp1729 Well-Known Member

Nov 23, 2015
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Good point!
He could possibly put together a switching regulator. One of the "Simple Switchers". You trade complexity and cost for heat and cheap.

20. ### Alec_t AAC Fanatic!

Sep 17, 2013
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1,136
For that current, the voltage converter is likely to be bigger than your "1 inch" you hope for.