Posted by Karl on
URL: https://www.es-forum.com/where-to-go-any-ideas-tp4034304p4034348.html

Casper, you're right. I should have checked the voltage drop before recommending that board. (It's 1.3V at 7.5A, 1V at 3.5A and 0.95V at 1A.)

>> ...I have not tested what the limit might be.

I don't know either, and it's difficult to figure out. Some chargers vary the output voltage:

http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html

(From that link: "One reason the charger has more control components than a typical charger is its variable output voltage. To produce 60 watts, the charger provides 16.5 volts at 3.6 amps. For 85 watts, the voltage increases to 18.5 volts at 4.6 amps. This allows the charger to be compatible with lower-voltage 60 watt chargers, while still providing 85 watts for laptops that can use it.[13] As the current increases above 3.6 amps, the circuit gradually increases the output voltage. If the current increases too much, the charger abruptly shuts down around 90 watts.")

USB type-C chargers with the "power delivery" feature do the same thing.

If your laptop will run from any 18V power supply, then you could replace the charger entirely with a 100W toroidal transformer and a linear regulator. (A 50W transformer might also work if your laptop draws less than 4A in real use.) But that would be more expensive, and you may not have enough space to place the transformer far away from you.

>> I also have another question about the steel used in your pipes.
>> Does it have to be some specific type of steel to shield EMF?

Not for the first layer of shielding around a transformer. Any kind will work there. But it needs to be thick (a few mm) to help measurably.

Electrical steel is better when the field is already weak, because it aligns with outside magnetic fields more quickly.

Usually it has more silicon and much less carbon, aluminum and sulphur than normal structural steels.

These articles are about related materials with similar metallurgy:

http://www.jfe-steel.co.jp/en/research/report/006/pdf/006-06.pdf
https://www.horizontechnology.biz/blog/iron-powder-types-permeability

>> (I live in Finland, so I have to try and figure out where the local metal super markets are)

There seem to be a lot of good suppliers in Britain. I assume that there are others in the Continent.

>> The Bourns inductor on your AC outlet; I assume the inductor is connected in series,
>> and the capacitor you put across live and neutral?

Yes, exactly.