Airsoft electronics - Today: MOSFET and you

HarryHirsch

PART I

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Hello and welcome to MOSFET and you!

MOSFET - What is MOSFET ? It stands for metal–oxide–semiconductor field-effect transistor. In other words, a transistor with a very low resistance.
What are the advantages of a MOSFET? It preserves the battery and it provides more power for the motor. How does it work? You can compare it with a relay. So if you pull the trigger the switch assembly switches the MOSFET and this switches the motor, because the the MOSFET has ha much lower resistance than the switch assembly, that means more power for the motor.

Next: Which parts do you need to buy from Maplin and how to put them together.

BioHazRd

Harry, while i applaud your initiative, I must point out some issues with your post.

yes, a mosfet does have low resistance, once it has been switched on, but unlike a standard transistor, you don't lose the .8 volt across it when activated. This is the main advantage over using a transistor circuit (consequently, more voltage would be available to the motor). I would also add that the switching speed of a mosfet is far quicker than a transistor

However you say that the mosfet has lower resistance than the trigger switch contacts, but this is not necessarily the case. When new, the resistance across the trigger contacts would be negligible allowing max current and voltage to go to the motor. Some times, with the high current involved, some trigger contacts will burn out causing higher resistance across the contacts. this will cause lower voltage and current to be available to the motor, and in some cases, a sticky trigger contact. A mosfet combats this by acting as a switch where we apply voltage to the gate (very low current across the trigger contacts required) which will allow the mosfet to pass high current through it, thus saving your trigger contacts.

so to be a bit pedantic, a mosfet does not preserve your battery, nor does it necesarilly mean more power to your motor - but it is a good thing to have if you can

tonky

Getting your facts right is never pedantic.:)
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Harry : Good idea. I've forgotten most of my Electronic theory (long ago) - Looking forward to more Airsoft related stuff. E.