Originally Posted by
Slide_me_crazy
Hey. As you can see from the title what are fets. I have like 3 long strips of them so like 30 or so and i know this size fet is for an xmod. But what does soddering them on do and allow the car to do. And is there such a thing as too many fets on 1 car
Long story short, they're a big electronically controlled switch. So now you're asking, why do I need that?
Your electronic speed controller is a microprocessor of sorts, and is a fairly dainty little thing. Capable of handling "a few ma" of power on any particular pin, at rather low (most likely 3.3v) voltages. Realisticly, the daintyier the better, as it will suck up less power you intend to use anywhere else.
Your Xmods will draw 4-5-12 amps of power, when you hammer the throttle. That processor that takes your radio singals and tries to control your motor, can only handle those few ma. But what you can do, is use that little bit of power, to control a LOT of power.
Transistors are the second tool we had to do that. They can take really small signals, and amplify how much work they can do. (first being tubes, but lets pretend those horrors aren't a thing.) Transistors require a fair amount of current to keep switched on. And the more power they pass, the more current they need.
That's a problem, since our dainty little ESC processor can only generate so much current, and that current needs to be at a proper voltage so the Transistor doesn't do something really sily. Like operate in a "analog" range. You can read "analog" as "heater". They don't like living there. (There's special transistors to help this, called darlington pairs...)
FETs are the solution to that. They are voltage controlled switches. Go above the right voltage, and they switch on, and switch on hard. And skip most of that analog region.
Transistors and FETs both have some resistance, and at the voltages you run, a few miliohms of resistance, is a BIG thing. By stacking FETs, you're dividing the resistance that the switching part of the circuit has. Two FETs have half the resistance... It also helps with the current carrying capacity.
FETs have current capacities, which if exceeded cause them to let the magic smoke out. That's where stacking them helps two. Having two FETs doubles the current carrying capacity of that part of the circuit.
Originally Posted by
biz77
A FET or MOSFET is a semiconductor. It has 3 pins. Think of them as an input, an output and a control pin (actual names are source, drain and gate respectively). It's basic job is to regulate current and voltage from the input to the output via information it receives through the control (gate). In an ESC, this is the component responsible for regulating the large amount of current that travels from your battery to your motor.
The ones the OP has, are actually 8 pins...