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Old 02-07-2006, 07:27 PM   #1
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Default Question about MOSFET

Not sure if this thread is in the right area, But seemed like it would work here.

My question is that a MOSFET works for a ESC, the same way a CMOS works for a computer system. This is what makes a ESC programable. If I and understanding the meaning of the MOSFET ( metal oxide semiconductor field-effect transistor).
If I am incorect which has happened once or twice before. LOL I am open to the right info.

Thanks Semore
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Old 02-07-2006, 07:36 PM   #2
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CMOS = Complementary metal oxide semi-conductor

CMOS is a PC is used in a PC to store the BIOS.
basic input/output system

Fet's in an ESC are used to as variable switches that allow current flow in steps.


Is this what your referring to?
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Old 02-07-2006, 07:49 PM   #3
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Well thats not what I was thinking but I understand better now, mosfet as what make you exelorate smoothly, and mantain a slower speed. Not the progaming of the profiles that are in the ESC.
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Old 02-08-2006, 12:06 AM   #4
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FETs are basically integrated circuit switches.
CMOS on the other hand is a way of making integrated circuits.

I'm pretty sure most FETs are an on/off sort of thing. This is why you have a drive frequency in your esc setup - the esc gives you partial power by switching the drive FETs on and off. The ratio of on to off controls how much of full power you get. The drive frequency is how fast it switches.

The control circuitry is the programable part of the ESC is not the FETs. The FETs are used to amplify the signals from some other control logic, possibly a embedded microprocessor like in a Schulze u-Force .

Here's a link to the plans for a simple airplane speed control SC6
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Old 02-08-2006, 12:36 AM   #5
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Quote:
Originally Posted by semore
Well thats not what I was thinking but I understand better now, mosfet as what make you exelorate smoothly, and mantain a slower speed. Not the progaming of the profiles that are in the ESC.
every ESC mostly consist of Mosfet IC's, Microcontroller/s, and BEC circuitry.

in automobile term, mosfet is equal to Fuel Injector, and Microcontroller is the car ECU,

mosfet is kind of on-off switch, in basic form such as IRF product, it has 3 pins : G (Gate), D (Discharge), S (Source), electric current flow in through S pin and exit through D pin, G pins control the currect flow
and driven by square pulse from on-board small programmable microcontroller,
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Old 02-08-2006, 01:43 AM   #6
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Quote:
Originally Posted by Faiz
every ESC mostly consist of Mosfet IC's, Microcontroller/s, and BEC circuitry.

in automobile term, mosfet is equal to Fuel Injector, and Microcontroller is the car ECU,

mosfet is kind of on-off switch, in basic form such as IRF product, it has 3 pins : G (Gate), D (Discharge), S (Source), electric current flow in through S pin and exit through D pin, G pins control the currect flow
and driven by square pulse from on-board small programmable microcontroller,
Good responese.

And to elaborate, the Mosfet aplifies a signal, basically the same way a car amplifier "amplifies" the signal from the receiver.

So, the microprocessors inside the ESC get a signal from the receiver to accelerate (from your controller) and so a microprocessor sends very low current pulses to the Gate. The ammount of current never varies, nor does the frequency from the microprocessor (unless you have a variable frequency ESC - some do that in response to the load). But it does vary the ammount of time that the pulse is "ON" for each cycle. Very short on pulses give low rpm, and longer ON pulses produce higher RPM.

Motors perform much better using ESC than just a resistor type of speed control for a couple reasons. First there is very little resistance in the circuit, so you are not losing power as heat through the speed controll.

Secondly, even at low speed (short pulses) the motor is still getting all available voltage, just on and off (off more) really really fast. So, at slow speeds, the motor will produce more torque with an ESC than with a resistor type speed control.
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