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

[Jake]

Oh, i guess I totally missed that Garrett was posting about PWM buck 
converters that are drop-in replacements for 7805, which is why the links 
contain "7805".  I looked them up and they are actually pretty cool:

http://pdf1.alldatasheet.com/datasheet-pdf/view/238738/CUI/V7805-500.html

sorry for assuming you were a n00b garrett.

-jake

On Tue, 8 Jan 2013, Jake 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
>
> 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
>> 
>> And the big brother for 1000mA:
>> http://www.digikey.com/product-detail/en/V7805-1000R/102-2178-ND/2352137
>
>