[Noisebridge-discuss] DC-DC Power conversion - Cheapish finds!

[Nicholas Granado]

it might be useful to examine (it was to me) the mintyboost circuit (uses a
buck converter). there's a great write up by ladyada here:
http://www.ladyada.net/make/mintyboost/process.html



nick


On Tue, Jan 8, 2013 at 5:27 AM, Jake <jake at spaz.org> wrote:

> For me, when i want a DC stepdown regulator up to an amp or so (maybe two
> amps) i just grab a cellular phone car charger.  They are all the same, a
> tiny circuitboard inside with a DIP version of the 34063 buck converter.
>
> up to 14 or 15 volts input, 5 volts output, just drop it in.  If you need
> a different output voltage, just add a resistor across one of the two
> resistors in the resistor-divider network.  If you need more than 15 volts
> input (up to 40v) just replace the capacitor with a higher voltage (unless
> it is already rated at least 10% higher than your working voltage).
>
> If you need more current, and/or want to be able to make buck converters
> from scratch, the LM2576 is great.  There is a fixed 5v-output version (so
> the only parts you need are inductor, diode, and two capacitors) or a
> variable output version (add two resistors to select voltage).  It's simple
> enough that you can put it together without a circuitboard if you're in a
> hurry.  Just ask Zach!
>
> The LM2576 goes up to 40V input, and the LM2576-HV goes up to 60V!
> Both can put out THREE AMPS of current.
>
> http://www.ti.com/lit/ds/**symlink/lm2576.pdf<http://www.ti.com/lit/ds/symlink/lm2576.pdf>
>
> Garrett, when you mentioned the 7805 you missed that we were talking about
> PWM-style buck converters, which are up to 90% efficient.  A 7805 linear
> regulator is basically just an automatic resistor which burns up the extra
> voltage, times the current you're using.  So, powering something with 5V
> from a 15V power source, you're literally burning off twice as much power
> as you're making use of (33% efficiency).
>
> -jake
>
>
> Garrett wrote:
>
>> This is better/cheaper for 5V 500mA from 6.5-36V:
>> http://www.digikey.com/**product-detail/en/V7805-500/**
>> 102-1709-ND/1828602<http://www.digikey.com/product-detail/en/V7805-500/102-1709-ND/1828602>
>>
>> And the big brother for 1000mA:
>> http://www.digikey.com/**product-detail/en/V7805-1000R/**
>> 102-2178-ND/2352137<http://www.digikey.com/product-detail/en/V7805-1000R/102-2178-ND/2352137>
>>
>
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