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If you want a topic covered e-mail me!
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This is the start of my robot wars dictionary, if you would like a topic covered in this area please e-mail me!, I make no guarantee for the accuracy of this page but if you spot any mistakes feel free to yell at me and I'll correct them... This is only intended as a basic introduction to various things used in Robot Wars
Q: What Is A MOSFET?
A: They are little electronic switches that have no moving parts and can switch on and off VERY quickly. MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor (in other words it's a fancy transistor). The reason it's so fancy is that whereas when normal transistors are on they have quite high amounts of resistance, when a MOSFET is on it has resistance of only 0.01 Ohms or lower. The reson that these are used in high power devices (i.e. big speed controllers) is that with a normal transistor the resistance at high current causes an awful lot of heat, MOSFETs however don't make so much heat and less power is lost. The main problem with MOSFETs is that the aren't realy switches and when the current is passing through them one way they don't work as well as when the current is passing in the other direction.
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Q: What Is Meant By A PWM (or electronic) Speed Controller?
A: PWM stands for Pulse Width Modulated, this means that instead of varying voltages going to the motor, varying pulses are sent instead. This means that the motor is being fed on/off pulses of electricity, the longer it is left on in each pulse determins how fast the motor turns. The beauty of this method is that even at low speeds full power is being applied to the motor all the time it is on. So, unlike the voltage reducing speed controllers (where lower speeds mean less power) the motor always has full power just at a different speed. Another advantage to this system is that there is a potentialy infinite number of different speeds available. In order to achieve such fast jumping between on/off you need a pretty quick switch and this is where MOSFETs come in, a MOSFET can switch all the power on and off very quickly whilst not loosing to much of it to heat.
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