# powering a project

Discussion in 'The Projects Forum' started by dmize, May 18, 2013.

1. ### dmize Thread Starter New Member

May 18, 2013
3
1
I am working on a project that requires to circuits to have power. I'd rather not have two power cords running to this project. If I could get one wall-wart to produce the power and then build a circuit to split the power and supply the correct amount to each circuit that would be ideal. I understand basic electronics (more from a troubleshooting side). I took courses in electronics almost 15 years ago, but I really haven't used much of it in the meantime other than basic troubleshooting.

The first circuit requires: 12VDC 4A

And the second circuit requires: 5VDC 1A

If anyone could tell me how to get started on this project I would be very appreciative.

Thanks,
Dan

2. ### #12 Expert

Nov 30, 2010
16,665
7,313

File size:
422.4 KB
Views:
19
• ###### LM7805.pdf
File size:
1.8 MB
Views:
6
dmize likes this.
3. ### GopherT AAC Fanatic!

Nov 23, 2012
6,303
4,026
Yes, the second circuit can be powered by the first. Just use the 12v source as the input to a LM7805 voltage regulator chip.

Unfortunately, I don't think you will find a 5 amp

4. ### kubeek AAC Fanatic!

Sep 20, 2005
4,687
805
The standard solution would be to use a linear regulator to get that 5V off the 12V supply, but that would waste 7W of power as heat and will be not easy to achieve. Also the 12V wall wart would have to be capable of delivering 5A which it probably is not.

5. ### MrChips Moderator

Oct 2, 2009
12,624
3,451
You can purchase a wall-wart that provides both 5V and 12V DC. Getting the right combination of amperage is going to be a bit tricky. Usually it is the other way around, 5V/4A and 12V/1A.

One possibility is to meet the 12V requirements, say 12VDC @5A and use a 5V@1A linear voltage regulator. That means having to waste 7W as heat.

Another solution is to use a 12VDC to 5VDC converter.

Finally, you can build your own dual supply with a suitable step-down line transformer.

May 18, 2013
3
1
7. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,143
768
Use an old Atx psu readily available to give out 5Volts and 12Volts and lots of current if you need it.

Easy to convert to bench psu just connect the Green wire to Black wire to make the psu work,
Red is 5v, Yellow is 12V, Black is Ground..Video

Last edited: May 19, 2013
8. ### dmize Thread Starter New Member

May 18, 2013
3
1
Thanks Dodgy, but I want this project to be slim in the end as something that be displayed. If it were going to stay on the bench that would be a great idea, thanks for your input though.

Dodgydave likes this.
9. ### Shagas Active Member

May 13, 2013
802
74
12 volts 5 amps ... mmm thats going to be expensive . Your local hardware store might not have such a power pack .
-I suggest finding a used Laptop switching power supply . They usually give 12-18 volts and 3-5 amps.
-Another good choice might be a cheap computer PSU which will give you the amps that you need . A cheap PSU will probably be much cheaper than a wall-wart (powerpack) with the amperage that you need

When you have that , then you can use LM317 (variable) or fixed LM regulators which are available at 5v and 12volts regulators for both circuits independantly .

Last edited: May 19, 2013
10. ### John P AAC Fanatic!

Oct 14, 2008
1,638
225
I don't think you will ever find a wall wart that produces that much power. An external "brick" is more like it. Stepping down 12V to 5V at 1 Amp output shouldn't be a problem, though.