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6-V to 5.2V linear regulator

Hello!

I would like to know how it is possible to make a linear regulator from 6-V to 5.2V. I have already made a little board like this (mine is with 6-V to 5-V regulator) on Youtube:


But the problem I'm having is that my device needs 5.2V and 5.0V is not enough. I want to make a linear voltage regulator, not any switching one.

Thank you!
, Pete.
 

bertus

Moderator
Hello,

A voltage difference of only 0.8 Volts will be quite a challenge.
The 7805 shown in the video already needs about 2 Volts difference.
The BA00CC0 needs only 0.5 Volts difference.

Bertus
 

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Hello!

I would like to know how it is possible to make a linear regulator from 6-V to 5.2V. ...

But the problem I'm having is that my device needs 5.2V and 5.0V is not enough. I want to make a linear voltage regulator, not any switching one.

Thank you!
, Pete.

Hi, Pete

Question: What's the source of your 6V input and how stable is it? For example, if it's unregulated or coming from a battery, it would be pretty fanciful to imagine that it's stable to 0.8V (13%) in the first place. Have you measured it under a 3A load or is this all theoretical?
 
The source is a normal 6-v battery. I would need 5.2V from it. 3A load is theoretical. I might get along with 1.5A.

Then even if it is a LARGE battery, you will likely NOT have a true 6V for input to the regulator -- at least not for long. For example, here's a typical discharge curve for an alkaline D cell. Note the immediate drop when the load is first applied.

main-qimg-b2be82a994828d342da316a7a59ce1ca


To see what reality holds in store for your battery, put a 4 Ohm (at least 10W) resistor across your battery and watch what happens with an accurate voltmeter.
 
The source is a normal 6-v battery. I would need 5.2V from it. 3A load is theoretical. I might get along with 1.5A.

PS: Having no idea what you think a "normal 6V battery" might be, I used 1.5V alkaline D cells as an example of a fairly "large" battery. Their typical nominal amp-hour rating is ~15AH. But as you can see from the graph above, a 6V battery made from four of them connected in series would drop below 4 x 1.3V = 5.2V in just a (very) few minutes when connected to a 2A load.

So the good news is you may not need a regulator at all!
 
Yes, normal battery can really mean anything. -:) When I said "normal battery" I actually meant huge 6V 140ah battery. And the reason why I want to use linear regulator is that I want to get rid of the EMF interference which normal switching DC-DC converters have.
 
Why not just put a diode in series?
Would approx 5.3V be too much?.


Martin
This sounds intresting! How do I put diodes in series? I'm beginner with these so I would need very clear instructions. -:) What kind of diodes? And is it 5.3V the lowest you can get from 6-V battery with diodes?
 

bertus

Moderator
Hello,

A standard diode will drop about 0.7 Volts.
A shottky diode will drop about 0.3 Volts.

Bertus
 
Your 6v battery could be as much as 7.0v when fully charged and possibly as much as 8v while under charge conditions.
How did you intend to deal with that aspect?
 
my device needs 5.2V and 5.0V is not enough.
....and just what 'device' is it that's so voltage critical?

We need ALL the information to make a reasoned response - if we end up saying 'you don't need anything, just use the 6V' after numerous posts we won't be thanking you for wasting our time.......
 
Yes, normal battery can really mean anything. -:) When I said "normal battery" I actually meant huge 6V 140ah battery.

That's good news. Then all you have to worry about is its temperature coefficient -- about -0.01V/oC if it's lead-acid, although you didn't say..
 
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