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Control direction of power flow and other things I don't know
(04-27-2019, 05:27 PM)revnarwhal Wrote: So a FET is sorta like a relay, except the charge that closes the relay also is the charge that passes through it?

Sorta, but not really. There are plenty of tutorials on youtube explaining how FETs work. The gate is triggered by voltage applied via the microcontroller. Altho, you don't "need" a controller to trigger the gate if you use a few other parts, like resistors and logic gates.
Some FETs only need, for example, like 5V to turn the gate on, but will allow 20V to travel through the switch. So they aren't "always" the same voltage. Other FETs act as variable gates depending on the voltage applied to the gate. For example, if 10V is fully closed, you could apply 5V to the gate and allow half as much current through the gate. so they could be used as current limiters as well.

I'm a bit rusty on the details, so the above may be slightly off. But again, there are a lot of YT videos that do some great explaining.
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(04-27-2019, 05:27 PM)revnarwhal Wrote: With regards to the magnets.  I had made some nickle strips with magnets on both ends for connecting batteries quickly in series or in parallel and without soldering. 
When will I have that USB port in my head where I can insert PDFs and EPUBs directly into my memory?!?!

So a FET is sorta like a relay, except the charge that closes the relay also is the charge that passes through it?

OK that magnetic thing is fine, - I thought you meant something different.  I think North or South pole matters only because the cell cases are steel & magnets don't like same poles facing each other.  Eg if you stuck the say north pole of a magnet to a cell, it would "extend" the north pole to the other end of the cell. If you then tried to attach another north pole magnet face at that end, they'd repel.

So yes a FET is sort of like a relay - the voltage on the gate "opens" (0V) or "closes" the relay (+10V, Nch type MOSFET).
Like Korishan says you can have in between partially on state but many power MOSFETs have a fairly sharp point from off to on, they're designed to be either off or on for switching circuit use.

The USB upgrade (join the Borg now) is no doubt coming soon :-)
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