Anyone? Step down converter from 13.8v to 5v

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LeeCavanagh
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Anyone? Step down converter from 13.8v to 5v

Post by LeeCavanagh » Mon Jan 25, 2021 12:39 pm

Does anyone have a simple circuit for 13.8v step down converter to 5v ?

Or recommend one
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Bton-FM
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Re: Anyone? Step down converter from 13.8v to 5v

Post by Bton-FM » Mon Jan 25, 2021 12:42 pm

5vreg.png
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LeeCavanagh
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Re: Anyone? Step down converter from 13.8v to 5v

Post by LeeCavanagh » Mon Jan 25, 2021 1:06 pm

Thanks bton-fm, Appreciated
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Albert H
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Re: Anyone? Step down converter from 13.8v to 5v

Post by Albert H » Mon Jan 25, 2021 3:31 pm

Minor changes - connect your 100nF caps right at the legs of the regulator, and use a couple of 4µ7 or 10µ electrolytic capacitors in place of the 10nF.

The 78L05 is only good to 100mA. If you need more current, you'll need a 7805 (good to an amp, but will need a small TO220 heatsink at more than about ½A. If you go for the heavier current device, you'll need the same capacitors to keep RF (in particular) out of the regulator.
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Re: Anyone? Step down converter from 13.8v to 5v

Post by Bton-FM » Mon Jan 25, 2021 6:37 pm

LeeCavanagh wrote: Mon Jan 25, 2021 1:06 pm Thanks bton-fm, Appreciated
What are you trying to power with this? I presumed it was a PLL?

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Re: Anyone? Step down converter from 13.8v to 5v

Post by Bton-FM » Mon Jan 25, 2021 7:04 pm

Albert H wrote: Mon Jan 25, 2021 3:31 pm Minor changes - connect your 100nF caps right at the legs of the regulator, and use a couple of 4µ7 or 10µ electrolytic capacitors in place of the 10nF.
That's how I normally do it with the legs soldered to the middle leg if its a 7805 on a tuner can or as close as possible if it's on a PCB. I guess it depends what it's powering to what the decoupling values are?

LeeCavanagh
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Re: Anyone? Step down converter from 13.8v to 5v

Post by LeeCavanagh » Mon Jan 25, 2021 7:49 pm

Bton-FM wrote: Mon Jan 25, 2021 6:37 pm
LeeCavanagh wrote: Mon Jan 25, 2021 1:06 pm Thanks bton-fm, Appreciated
What are you trying to power with this? I presumed it was a PLL?
Oh, a tiny pll which only gives out 100mw
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LeeCavanagh
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Re: Anyone? Step down converter from 13.8v to 5v

Post by LeeCavanagh » Mon Jan 25, 2021 7:51 pm

I did consider using a cigarette lighter to usb charger which i have spare, that give out 5v more than enough amps too
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Re: RE: Re: Anyone? Step down converter from 13.8v to 5v

Post by alfaeire » Tue Jan 26, 2021 6:49 am

LeeCavanagh wrote:I did consider using a cigarette lighter to usb charger which i have spare, that give out 5v more than enough amps too
Most of the time they give out a load of noise too. They can be used, but should be shielded.

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Albert H
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Re: Anyone? Step down converter from 13.8v to 5v

Post by Albert H » Wed Jan 27, 2021 3:31 am

Be REALLY careful with the filtering on the supply if you use the 5V adaptor. They frequently put out ~100kHz ripple, which can appear as spurs on your carrier!
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Re: Anyone? Step down converter from 13.8v to 5v

Post by rigmo » Sun Jan 31, 2021 12:30 pm

do not forger electrolyte capacitor
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Re: Anyone? Step down converter from 13.8v to 5v

Post by rigmo » Wed Mar 31, 2021 11:17 pm


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