# 24v to 12v

Discussion in 'General Electronics Discussion' started by JMods, Aug 5, 2011.

1. ### JMods

5
0
Aug 5, 2011
Hi

I'm trying to power a laptop from using the battery connector as the wall socket connector board is broken, but it's not worth replacing.

So I need to convert 24v DC to 12v DC and then either 12v DC to 5v Dc or 24v DC to 5v DC - two separate outputs.

I'm handy with a soldering iron so if I could make a circuit myself that would be best.

Any help would be appreciated

Thanks

Julian

443
3
Jun 10, 2011
Why not buy two 5 V wall warts that supply the needed current (which you didn't specify)?

3. ### JMods

5
0
Aug 5, 2011
Hi

Thanks for your reply, I would prefer to use 1 psu and since i have the one that came with the laptop, i would prefer to use that, but i will see if i have any 12v psu's in the cupboard - thanks for the idea.

Julian

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,418
2,788
Jan 21, 2010
So you need 12V and 5V (typical for a PC by the way).

You need to determine the current required from each rail -- your power supply may tell you what it's rated at. If your power supply is not helpful you will need to measure each rail and determine what the maximum current required from each is (this is not straightforward since you may not manage to create the situations that require peak power).

With this information we may be able to help you a little more.

Do you want to run the PC from 24V or 12V? If you want both it may be more efficient to create 2 different power supplies.

Also is either/both of these a lead acid battery or a vehicle power system? (What is the source of the 12/24V?)

5. ### JMods

5
0
Aug 5, 2011
Hi

I want to power the computer using 12v which will be supplied by the 24v power supply using some kind of step down transformer. The source of the 24v is the power lead that came with the computer, and the source of the 12v will be the same.

Hopefully this helps

Julian

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,418
2,788
Jan 21, 2010
OK, well the first thing to do is to determine the current requirements for the 12V and 5V rail.

7. ### JMods

5
0
Aug 5, 2011
Hi

How would i do that?

Julian

8. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,418
2,788
Jan 21, 2010
Measure the current draw under a variety of conditions and try to determine the maximum value for each.

The original power supply may have some indication of its rated output which would be an easier option.

9. ### JMods

5
0
Aug 5, 2011
Hi

The output is 24.5v at 2.65A

Julian

10. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,418
2,788
Jan 21, 2010
No, you need to measure the REQUIRED power on the 12V and 5V rails.

11. ### TBennettcc

292
2
Dec 4, 2010
Typical laptop power supplies run about 90 watts... do you happen to have the original power adapter for your laptop? How many volts and watts does it supply?