TeaAddict
Posts: 27
Joined: Mon Oct 15, 2012 11:12 pm
Location: Florida, USA

5V Regulation

Tue Feb 19, 2013 12:59 am

I just wanted to make sure this setup is safe before I try it.

Using a pack of 8 alkaline batteries (12V) or 8 NiMh Batteries (9.6V), and a 5V regulator, probably with a heatsink:

Image

I've heard some people say you should add capacitors, but some places say you don't have to. Is it necessary in this case?
n00b at electronics, n00b at programming...

But EXPERT at asking questions

klricks
Posts: 7154
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: 5V Regulation

Tue Feb 19, 2013 3:29 am

I would use the 9.6 V batteries if you can because not as much power is wasted as heat.
The 7805 efficiency drops off dramatically at higher input voltages.
You probably don't need capacitors if using batteries.

I would look into using switching or 'buck' type regulator instead.
Kind of expensive but you won't need a heat sink and your batteries will last way longer.
Efficiency is nearly the same in relation to the input voltage so higher input voltages don't matter nearly as much.
They also typically have a lower dropout voltage.

Here is one example of a completely self contained 'buck' type switching regulator:

5V version:
http://www.dimensionengineering.com/products/de-sw050

or adjustable version:
http://www.dimensionengineering.com/products/de-swadj
Unless specified otherwise my response is based on the latest and fully updated RPiOS Buster w/ Desktop OS.

sim_tcr
Posts: 331
Joined: Tue Nov 06, 2012 1:01 pm
Location: Bangalore
Contact: Website

Re: 5V Regulation

Tue Feb 19, 2013 7:48 am

Few months back, I had tried to power the pi from a battery using step down method. I never could complete the project. But here are few details on it.
LM317 and 7805 are old linear ICs and their efficiency is very low, they get heated up very fast.
LM2596S-ADJ (switching regulator IC) would be the best choice. (original discussion here http://www.raspberrypi.org/phpBB3/viewt ... 63&t=26532)
You also get ready made DC to DC Step Down Adjustable Power Supply Module using LM2596S such as this one http://fabtolab.com/index.php?route=pro ... uct_id=142. Its very cheap.
http://raspisimon.no-ip.org
Raspberry Pi Model B x 2, Raspberry Pi 2 x 2, Transcend 32GB Class 10, Transcend 16GB Class 10, Transcend 8GB Class 4, Custom 12V 1.5A (stepped down to 5.5V)

Return to “General discussion”