[time-nuts] Power supply for OCXO using "USB power blocks"

[Taka Kamiya]

Let me try it.  I have a few of those 5V USB power supply.  I have on my desk, DC/DC converter that will take whatever to whatever.  Got a dozen from Amazon.  I'll set it to 12V.  I'm sure it will work in some fashion.  I've used unknown power supply (switching type) for various things, and I have yet to see it in any meaningful way in output.  But, measure it well enough, I'm sure it is there.  I'm also interested in re-using those laptop power supplies.  

Only problem is, each one is SO different.  My result won't apply to you or anyone else.  A few months ago, Apple actually did a recall on counterfeit products.  I think a person died or house burned down or something of that nature of what was supposed to be a genuine product - except it was not.  An amazing response from Apple.

But, I'm curious enough now.  I'll try apple kind and generic kind.  What shall I look for?  Load it up to say 100mA and measure voltage and ripple?  I wonder if I should put DC de-coupling and put it though an audio frequency FFT?  I'd expect NOT to see 60Hz anywhere but probably few 100KHz.

I will report back in few days.

--------------------------------------- 
(Mr.) Taka Kamiya
I'm stuck in a wormhole....  Hello, worms! 

    On Sunday, March 10, 2019, 7:00:12 PM EDT, jimlux <jimlux at earthlink.net> wrote:  
 
 On 3/10/19 12:07 PM, Achim Gratz wrote:
> jimlux writes:
>> How quiet is the output from those USB battery things..I've used one
>> to run a RTL-SDR, but that's hardly a ultimate low noise receiver.
> 
> Depends, but I suspect that most of them favor cheap over quiet -- they
> do already have a DC-DC in there that gets whatever the accumulator
> voltage is to 5V.  I also have one of these that is really noisy when it
> has no load, but seems to be OK when I start pulling a few mA.
> 
> Plus, chaining DC-DC like you outline really isn't helping efficiency
> wise.  Unless you already have a bunch of USB power banks you want to
> reuse (I'd still think about just using the cells then), perhaps have a
> look at some of the stuff that the RC model crowd is using.




it was the idea of reuse of the ubiquitous USB 5V sources, whether line 
powered or battery powered.


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