pcdangio
Posts: 21
Joined: Wed Oct 01, 2014 10:17 pm

Separate Switching Regulator for Pi Power?

Sat Feb 14, 2015 1:23 am

Hello.

My Raspberry Pi is going to be controlling a large number of LEDs that can draw up to ~7A max. My power supply is 12V, and I'm using a step-down switching regulator (rated for 10A) to step the 12V down to 5V. The LEDs and the Pi will both be running off of 5V. Now my question is, should I get a separate switching regulator just for the Pi? I'm worried that current spikes from the arbitrary LED use will mess with the Pi if they are both drawing 5V from the same regulator.

Thanks!

jimallyn
Posts: 51
Joined: Wed Nov 12, 2014 9:13 am

Re: Separate Switching Regulator for Pi Power?

Sat Feb 14, 2015 2:47 am

Most switching regulators are pretty well regulated, and respond quickly to changes in load. Unless you plan to switch all of the LEDs on or off at the same time, I wouldn't think it would be a problem, and even then it might not be a problem.
“So you say you love the poor? Name them.” - Gustavo Gutierrez

drgeoff
Posts: 9748
Joined: Wed Jan 25, 2012 6:39 pm

Re: Separate Switching Regulator for Pi Power?

Sat Feb 14, 2015 2:29 pm

If you do experience problems try putting a couple of thousand microfarad capacitor across the 5 volt supply at a place close to the LEDs.

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davidcoton
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Location: Cambridge, UK

Re: Separate Switching Regulator for Pi Power?

Sat Feb 14, 2015 10:16 pm

drgeoff wrote:If you do experience problems try putting a couple of thousand microfarad capacitor across the 5 volt supply at a place close to the LEDs.
Or even better, as close to the Pi as possible. It's the Pi that needs the uninterrupted supply, putting the capacitor near the LEDs means it has to supply their current to avoid propagating a dip, whereas putting it near the Pi means that the dip will arise but not get through to the Pi. Note this is because the supply cables have a significant resistance -- if they were perfect conductors the position of the capacitor would not matter.
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jimallyn
Posts: 51
Joined: Wed Nov 12, 2014 9:13 am

Re: Separate Switching Regulator for Pi Power?

Sat Feb 14, 2015 10:25 pm

Also, some power supply circuits can be unstable with too much capacitance on them.
“So you say you love the poor? Name them.” - Gustavo Gutierrez

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