# how can i convert 24v to 12v?

#### CornyCorn

Joined Feb 13, 2016
12
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!

#### panic mode

Joined Oct 10, 2011
1,848
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.

#### ScottWang

Joined Aug 23, 2012
6,926
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.

#### dl324

Joined Mar 30, 2015
11,263
Welcome to AAC!
I will need to turn 24vdc into 12vdc, but i want to use something that:
-will not generate heat
Don't want to discourage you, but what you want to do is not possible. Even the most efficient regulator will generate heat.

#### Lestraveled

Joined May 19, 2014
1,946
...... Even the most efficient regulator will generate heat.
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"?

#### CornyCorn

Joined Feb 13, 2016
12
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"?
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

#### hp1729

Joined Nov 23, 2015
2,304
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
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..

#### dl324

Joined Mar 30, 2015
11,263
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?
If you specify your current requirement(s), you'll get more appropriate suggestions.

#### Alec_t

Joined Sep 17, 2013
11,520
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?

#### Evanguy

Joined Dec 21, 2014
81
A simple buck converter should work for you. there are some circuits on google or they can be had on ebay for about 2$i assume you will be drawing less then a few amps. some even with led screens to show output as they can be varied #### Dodgydave Joined Jun 22, 2012 9,313 Lm7812, Lm7805, Lm2596, Lm317, all of these regulators will work, but until you give your current limit, we just keep guessing. #### AnalogKid Joined Aug 1, 2013 8,536 Where are you located, and what is the general nature of your invention? ak Thread Starter #### CornyCorn Joined Feb 13, 2016 12 Lm7812, Lm7805, Lm2596, Lm317, all of these regulators will work, but until you give your current limit, we just keep guessing. The current draw will be around 1-2 amps. Thread Starter #### CornyCorn Joined Feb 13, 2016 12 A simple buck converter should work for you. there are some circuits on google or they can be had on ebay for about 2$ i assume you will be drawing less then a few amps. some even with led screens to show output as they can be varied
Are there any models that you recommend? I prefer to have ones with PCB pins.

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#### hp1729

Joined Nov 23, 2015
2,304
Are there any models that you recommend? I prefer to have ones with PCB pins.
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.

#### GopherT

Joined Nov 23, 2012
8,012
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.
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.

#### dl324

Joined Mar 30, 2015
11,263
The current draw will be around 1-2 amps.
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.

#### ScottWang

Joined Aug 23, 2012
6,926
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.
Did you see the current he needed -- around 1-2 amps?

#### hp1729

Joined Nov 23, 2015
2,304
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.
Good point!
He could possibly put together a switching regulator. One of the "Simple Switchers". You trade complexity and cost for heat and cheap.

#### Alec_t

Joined Sep 17, 2013
11,520
The current draw will be around 1-2 amps.
For that current, the voltage converter is likely to be bigger than your "1 inch" you hope for.