Re: where to go ? any ideas ?

Posted by Karl on
URL: https://www.es-forum.com/where-to-go-any-ideas-tp4034304p4034316.html

The type of inductor didn't matter as much as I was expecting. The ones in the video are these:

https://www.mouser.com/productdetail/jw-miller/2200ht-102-v-rc?qs=vHwXmp3ZSzbSLwSr5MNnyw%3D%3D

They're connected in series with the fan - the plus-side current passes through one, and the negative-side current passes through the other.

I've also used larger Bourns inductors:

https://www.digikey.com/product-detail/en/bourns-inc/2324-H-RC/M8847-ND/775386

...as well as these:

https://www.ebay.com/itm/233033066308 (I found them by searching for "toroidal inductor.")

All of those worked well for the fan, but none of them worked as well on the AC side of a switching 5V charger. Inductors as big as 8 mH performed about the same in both situations. I should test some small ones with the fan to find the minimum useful size, but I haven't done it yet.

About your laptop power brick: The small Bourns toroids will probably get too hot. Even the larger ones (second link) are only rated to 2.4 amps. You can run two inductors in parallel to handle twice the current with half the inductance if you need to.

If you run inductors on AC, they'll get hotter. I'd also cover them with electrical tape or heat-shrink insulation if the manufacturer doesn't list a maximum voltage.

The little capacitors in the video were these (metallized film capacitors rather than electrolytic capacitors):

https://www.mouser.com/ProductDetail/Panasonic/ECQ-UAAF224M?qs=sGAEpiMZZMu3dWSqd4Tl0P8JmQac6bjpnrc8j0jdlD4%3D

Supposedly the reason they worked as well as the large ones is that they have lower internal resistance.

https://en.wikipedia.org/wiki/Equivalent_series_resistance
https://xtronics.com/wiki/Capacitors_and_ESR.html

Their other advantage is that they won't explode if you reverse the + and - terminals.

I haven't built RC filters. They seem to be common in low-current devices like ADSL filters. LC or RLC filters seem more common in high-current devices.

You can compare them here:

https://electronicbase.net/low-pass-filter-calculator/
http://sim.okawa-denshi.jp/en/RLCtool.php

...and you can use this to predict how much power the resistor in an RC, RLC or RL filter will consume:

http://www.ohmslawcalculator.com/ohms-law-calculator