MOSFETs

[Ward8124]

Hey peeps whats the deal with these and what's your experiences with them? Are they for rapid fire on the trigger or just better at closing the circuits? Anyone fitted one to an GR300?

[Oli]

Re: MOSFETs

they are in reality nothing but a posh switch, imagine no contacts, just a straight through cable from your battery to your motor.

this is what a FET does basically, the open and close command comes from the traditional trigger switch, which functions as a low voltage gate.

you only really need them in the current draw is very high, ie when your using a big spring for high fps.

for fast rate of fire, you don't really need them, just good quality wire and good quality connections all around will do the trick.

[Ells]

Re: MOSFETs

they offer better trigger responce, higher r.o.f, contacts won't burn out, and allow you to use a small gauge wiring in certain parts of the circuit.

[rik]

Re: MOSFETs

A MOSFET is an electronic switch. It takes power in through one leg and emits it through a different leg if and only if it gets a small amount of power in through the third leg of the three. This is useful for an AEG because we want to control high current loads to drive the motor. The cheap way to do this is to use the trigger switch to do the whole job. This means that a lot of current goes through contacts just as they connect and corrode the edges. Basically it wears them down. If you put a MOSFET in then you can avoid that by having only a very small current go through the switch and use that current to the third leg in the MOSFET to control the power from the battery to the motor. Because the current is now taking a nice short electrically clean path from the battery through the MOSFET to the motor and back it is also a lot more efficient which means the motor will run a little better, meaning faster and possibly harder.

Manufacturers not putting a MOSFET in is a cost reduction on parts. Adding the MOSFET yourself will help with reliability (because of not putting large currents through the switch contacts anymore) and efficiency (because the resistance is lower through the MOSFET than a mechanical switch).

[amandla36]

Re: MOSFETs

Some MOSFETS will also allow you to do cool stuff like add three round burst capability to your weapon :D
EDIT: It usually replaces full auto though.

[rik]

Re: MOSFETs

That's a MOSFET with some extras. These are available too but more expensive.

[jagillham]

Re: MOSFETs

If you get a MOSFET you might aswell get an 'Active Braking' one. AB MOSFET.

These ones stop the motor after one spin, making for nice clean feeding. What can happen on rapid semi, or high speed set ups is the motor does one spin, and then continues half into the next cycle.

If you like semi auto, want a little up in ROF or are running a 9.6v battery then an AB MOSFET is a good investment.

[sniperiain]

Re: MOSFETs

yer i have a mosfet. it makes a huge difference on trigger responce. only problem. i cant get it to feed:P

[sj_asc]

Re: MOSFETs

for fast rate of fire, you don't really need them, just good quality wire and good quality connections all around will do the trick.

MOSFETs are beneficial for both high speed and high FPS builds, if anything, more so towards high speed setups, particularly those with High speed Motors and or High speed Gear sets.

As has already been said, they basically hammer the wiring resistance down to a minimum in order to achieve better efficiency(providing you use a decent FET), and as the main current switch is solid state, there is no arching form mechanical contact.
The majority of the current is directed away from the trigger switch, so the arching that causes heavy wear and increased resistance is no longer present.

There are motor controllers out there that offer variable burst fire, speed levels, different cutoff switches, soft braking, and full cycle completion etc..., but all cost money.

Active braking MOSFETs,
Works by shorting the motor when the power is cut (semi auto) to deaden the counter electromotive force, effectively stopping the motor dead at the point of cut off rather than let is slow down.
The original ABs cause more wear on the motor comm and brushes.
To simplify it, you can generate electricity by turning the rotor, the residual momentum that is left when the power is cut is still generating electricity which is being shorted out by the MOSFET when the power is cut.
The moving contacts in the motor (comms and brushes) make the mechanical short which produces an arc, often much bigger than that of the startup arc which causes pitting + carbon buildups (basically increasing wear)
The more recent designs have "soft braking" which IIRC is an addition of a resistor rather than a straight short. Often the voltage spikes from the motor when braked were killing the braking FET.

For those on budget with extreme speed setups, I will not put anyone off getting an AB FET. Sure I've had one of Franks original AB MOSFETs in an older setup, and it may have sped up wear an tear on my motor, but it certainly was far better than double shots. For those who want solid state switching with average ROF, I advise sticking with the basic single MOSFET switch, just make sure the MOSFET its self is decent (something 1404 or 3034 based would be ideal )

[jfox61]

Re: MOSFETs

Does anyone know of any "how to" forums or instructions for doing this yourself?

[sj_asc]

Re: MOSFETs

Does anyone know of any "how to" forums or instructions for doing this yourself?

Would that be installation instructions, or how build your own MOSFET Switch?

[sniperiain]

Re: MOSFETs

i do mate:D can PM you it:D

[jfox61]

Re: MOSFETs

Install instructions are what I am after. Also any suppliers of these mosfets in the UK as I tried Maplin and they don't do them. Sniper Iain that would be great if you could pm with the instructions. Quoted 60 quid for installation inc cost of a mosfet and about 20 quid extra for programmeable. I am sure I can do it for a lot less.

[jagillham]

Re: MOSFETs

Maplins will sell the component parts, you'll need to solder it together!

Most the MOSFET's I have seen are from the USA, but the postage is quite reasonable. Look out for Infected as a user on arnies.

[Caveira]

Re: MOSFETs

http://infectedairsoft.wordpress.com...tive-breaking/