On Thu, 10 Jan 2019 12:45:25 +0000, Andrew Gabriel wrote:

> I've used car/truck cigarette lighter adaptors for years.
> Usually, I pull out the guts and put it in my case with the Pi.
> The truck ones are 12-24V input.
>
Same here, mainly so I could use soldered 12v connections rather than the
horrible alternative of using cigar lighter socket on a flying lead and
strapping the converter in with insulation tape so it couldn't leap out
of its socket at an awkward motive. I also put the lot into a metal box
(rather than plastic) to limit RF noise from it and (paranoia!) added
ferrite cores to its input and output cables.

> They work, but they generate so much RF noise the WiFi was unable to
> work on the Pi. None had any output filtering other than just the single
> electrolytic capacitor.
>
The 12v -> 5v@3A converter I'm currently using was bought because the
cigar-lighter converters have vanished from eBay. Its installed inside
the same metal box that used to contain the old converter and with the
same ferrite cores on the external wiring.  Again, no RF interference
despite being mounted less than 10 cm from my glider's airband
transceiver.

> WiFi working. Went back to a car cigarette lighter adaptor, which works
> fine. (A friend told me some of the car adaptors have bad RF radiation
> too - he used them in a glider to power a GPS, and you would get the odd
> bad one which killed the GPS signal.)
>
I never saw that - probably because I thought it might be an issue and
put it inside said metal box.

FWIW the only bad source of RF I've had came from the mechanical
turn&bank I carry when it was first fitted. That was silenced by putting
a capacitor across its power leads: one that Maplins sold specially for
suppressing sparking from motor commutators & brushes. Fitting it
immediately got rid of all the noise.


--
Martin    | martin at
Gregorie  | gregorie dot org

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