FET explaination
 

There seem to be so many questions about fets that i thought i would explain what they are and what they do. I'll try to make it make sense...let me know if it needs more.

Not copied or pasted, these are my words. Fets, or field effect transistors control the power that is put out to your motor. You can search for pics but they are easy to pick out...they are small black squares with 3 shiny terminal coming off of them soldered to the board, there are 2 of them. They are gated and pretty much controlled by a square wave (-_-_-_-_-_-) when turned on they allow current to flow and when turned off they stop said current. The frequency or amount of time they are on compared to off determines how much current is fed to the motor. The power that goes to the motor is therefore actually pulsed but at such a great speed that it becomes seamless. A stock fet can only handle so much current so stacking doubles the available current (does not however double speed). The same goes for larger or upgraded fets. This is a pretty general and low tech explanation but I feel it should answer most questions about fets and stop the endless questions about them.

that helps out alot tho!

Very good explanation! That clears up many things for me!

correct me if im wrong but is a fet sort of like a anti resistor (opposite of a resistor) this is just me seeking more intellectual understanding not saying thats what it is just inquiring...

good job on the fet explanation!

Think of the fets as the spigot that your garden hose is hooked to. The more you turn it on the more comes out. The opposite of a resistor would be an amplifier.

good stuff... i was just wondering... i guess i dont get the whole fet concept...

What dont you get? The whole point of this was to help you understand so i failed if you dont get it:)

no i understand what they do...just not why they are there...

They are there for speed control, without them (using old school technology) the size of an xmod would be impossible. An old 3 step servo controlled speed controller would take up nearly half of an xmod by itself.

yeah don't worry about it im one of those people who like to have a complete understanding of things... i like to know things its weird... thanks for helping though...

know i get what they do but when i went from stock to 2x2 it seemed like there was more torque is this true or was i just excited

true...that is the whole purpose of stacking them...to allow more current flow (torque)

when i upgraded i reused to stock fets and stacked them on another vehicle with great performance changes.

Cheers for this, I had no idea what FETS were and was gonna search google but I found it here :D

97Supra? Are you on other forums?

FET's have limit current on some board. For example, the Micro-T. No matter how much current you feed the board, the motor still only gets 2.9v... I'll talk to ph2t about more on this, but I recall him saying this about the Xmods and Mini-Z boards as well...

I never said fets would increase voltage to the motor...that is impossible. Current on the other hand can be increased.

Er. Sorry. It's hard to explain, but the FET's on some cars limit the amount of VOLTAGE the motor recieves, meaning no matter how many batteries you get, it will still run the same, maybe just cooler... Not sure of this on the xmods, but I'll get back to it..

Once again...fets can not limit voltage...the circuitry that controls them however can but fets are basically just a switch which you could pass 1000 volts through if you so chose. Maybe you should stop relying on other sites for info and just post what you know.

Not sure if this is off topic, if so sorry, but does it matter when stacking fets if its an evo or a gen1 cuz i want to stack fets on my mustang evo

I'm a total newb to all this stuff, and electronics in general. Is there any way that you could post a pic of what FETS are, or something? :blush: