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Re: [Phys-L] AC power calculations

On 2021/Feb/22, at 13:06, Daniel MacIsaac via Phys-l < <>> wrote:

Actually Bernie, there are a lot of cheapie power supplies out there using capacitive droppers to avoid the transformers in wall warts. Many LED lamps use these.

If you buy a super cheap (eg quite lethal when wet) $2 cell phone charger that’s for sure a capacitive dropper. The Apple charger costs 10X as much, but is much safer (real HV isolation).

Dan M <>


I obviously miscommunicated.

I meant as a load, i.e. the cap. across the AC domestic power. I may try that again to verify.

One may test if a cap is the connection to the wall wart or a better high freq W/toroid v. low standby consumption P/S (< one watt) if it sparks on connection. The 65 W apple book P/Ss (curiously) does this! The usual, now ancient, transformer types don’t, and standby is often about 4 W.

bc uses his kill a watt v. often. He's taken apart many wall warts, but not yet a “modern” one. (Too valuable and usually potted. He does not like potted electronic.)

BTW, I previously used a d’ Arsenal type watt meter, but now in the to be repaired box. They’re very interesting: The W/Q [1] is the armature, the current is the magnet. Smart, nicht wahr?

[1] I suppose nearly universally voltage, which makes as much sense as using feeterage or meterage for length. But then using voltage indicates not abvolt or statvolt. OTOH, coutures use yardage. Oh, I can use pd, except w/q is specific potential. The English maybe use tension especially in EHT The French tension, and the Germans a very long word, typical! (according to google translate)