Mosfet -What's the point?

[sonofsammo]

I'm still new to this, so am clueless on AEG's still.
It looks like people recommend mosfets, but even after reading about them (I was looking at the gate titan), I still don't understand why I'd want one.
Anyone got any links to good info?
Any opinions on why you have to have a mosfet?
What are the benefits?
Thanks in advance....

 

[Iceni]

A mosfet does one important thing. It protects your trigger contacts.

An AEG runs at 7.4 to 11.1 volts. And will draw 10-20amps of current. Enough to cause sparks.

In a regular AEG circuit the trigger contacts act under full load. And because those are parts that move together there is a chance of sparks where they meet. Over time this sparking causes the trigger contacts to either go black or to burn out.

A mosfet in contrast is a non moving switch. It uses a semiconductor to act as an open/closed gate. And in order to actuate the gate you take a low current feed from the battery to the contacts. So the contacts don't arc and burn out, and because the mosfet has very little resistance compared to mechanical switches you also gain a slight trigger response improvement.

A basic mosfet like an xcoretech xet304u is more than enough for most aeg's.


The second stage of mosfets is active braking. These stop the motor dead with back current. You fire, motor spins, then once the shot is complete the back current stops the motor. This is useful for high ROF guns where you might get 2 or more shots from a single trigger pull because the motor is running on.



More advanced Mosfets do more.

Contact protection
Active brake
Self regulating fuse
Low battery cut out.
3rd burst
ROF adjustment
Variable burst mode
Adjustable trigger

The more expensive you go the more options those units have. All you really need a mosfet to do however is the basic contact protection... Everything else is just features.

All of my guns run basic mosfets. 3 are on the Xcoretech xet304u style (there are numerous companies making this design check AK2M4). The others have home made units. And one has a Gate Nanohard because that gun needs the active braking and that fet lets you turn it on and off, and as an added bonus is has the low battery cut out.


That low battery cut out is quite good if you are new to lipo's. It'll stop the gun shooting once the battery is done. The gate nanohard can be programmed to be on off and has settings for all common lipo voltages.


Edit:

Just a note about batteries.

Lipo's are more prone to contact blackening and burning out because of how they deliver current. A lipo dumps current very quickly hence they give better trigger response as the motor doesn't have to wait for the current to creep up.

Nimh batteries can't release the current so quickly, They have a slight ramp up time, rather than a dump. This means whilst they can still provide more than enough ampage they have a softer less sparky effect on the trigger contacts. At the cost of initial motor performance.
 

 

[sonofsammo]

A mosfet does one important thing. It protects your trigger contacts.

An AEG runs at 7.4 to 11.1 volts. And will draw 10-20amps of current. Enough to cause sparks.

In a regular AEG circuit the trigger contacts act under full load. And because those are parts that move together there is a chance of sparks where they meet. Over time this sparking causes the trigger contacts to either go black or to burn out.

A mosfet in contrast is a non moving switch. It uses a semiconductor to act as an open/closed gate. And in order to actuate the gate you take a low current feed from the battery to the contacts. So the contacts don't arc and burn out, and because the mosfet has very little resistance compared to mechanical switches you also gain a slight trigger response improvement.

A basic mosfet like an xcoretech x304u is more than enough for most aeg's.


The second stage of mosfets is active braking. These stop the motor dead with back current. You fire, motor spins, then once the shot is complete the back current stops the motor. This is useful for high ROF guns where you might get 2 or more shots from a single trigger pull because the motor is running on.



More advanced Mosfets do more.

Contact protection
Active brake
Self regulating fuse
Low battery cut out.
3rd burst
ROF adjustment
Variable burst mode
Adjustable trigger

The more expensive you go the more options those units have. All you really need a mosfet to do however is the basic contact protection... Everything else is just features.

All of my guns run basic mosfets. 3 are on the Xcoretech x304u style (there are numerous companies making this design check AK2M4). The others have home made units. And one has a Gate Nanohard because that gun needs the active braking and that fet lets you turn it on and off, and as an added bonus is has the low battery cut out.


That low battery cut out is quite good if you are new to lipo's. It'll stop the gun shooting once the battery is done. The gate nanohard can be programmed to be on off and has settings for all common lipo voltages.
 

I've only got two AEG's at the mo - An ARP9 and a Krytac Vector...
Afaik, they have mosfets as standard.
I've got an SVU on the way and was wondering if it was worth putting one in that. Sounds like it will be, but there doesn't seem like much point going for an expensive one - so thank you! You just save me dosh ? 

The other thing to ask is - how easy are they to fit? For someone with zero knowledge of AEG internals, that is....

 

[Iceni]

It's a bit of soldering. And some heat-shrinking. Nothing super technical.

But and this is a big but!

You will have to open the gearbox on a version 2. And you will have to put in 2 lightweight trigger wires, and the feeds  to the  motor. It's not hard but it can be frustrating. If you have any doubts at all. Pay some fecker to do it for you.

 

[ImTriggerHappy]

Just buy a titan 

 

[sonofsammo]

Just buy a titan 

This is what precipitated my OP.

But at sixteen times the cost of what @Iceni is suggesting, I can't see getting my money's worth...

 

[Adolf Hamster]

first job is protecting trigger contacts, not so big a deal if you're handy and have a reasonably common gearbox, but especially if it's something a bit different then you might not want to replace the contacts after 6 months of usage on lipo.

second benefit is battery protection, you can reasonably estimate a lipo going by a sudden drop in rof but if you keep pewing after than you can permanently kill your battery, a decent mosfet will just cut you off.

third benefit (for the fancier systems) is things like active braking and features like 3rnd burst, great for that extra trigger response.

final benefit (specific to titan and mosfets that use opto connectors) is it takes much of the rube goldberg gubbins of your mechanical trigger mechanism and replaces it with optical sensors, less wear and tear on the gearbox internals, less friction for even snappier response, and you can do things like set the trigger sensitivity to the point where breathing on it can set it off. you can also set rof, for example a fast motor setup you can have ultra snappy semi auto but dial back the full auto rate of fire to a manageable level.

ice is right, for most common aeg's i'd say a basic mosfet is a must for using lipo to save the contacts, titan's and their ilk are cool for those who want to push the limit of what can be acheived in an aeg and if that's your thing then it'll be worth the money, but the basic protection is good enough for most.

 

[ImTriggerHappy]

This is what precipitated my OP.

But at sixteen times the cost of what @Iceni is suggesting, I can't see getting my money's worth...

Yeah you will it transforms your gun. 

You will get precocking so instant trigger response.  Programmable burst fire. It completely replaces your trigger mech so no more slugish connection just a light sensors so you end up with short trigger pull and no more crappy cut off lever. There are a whole host of other features you can play with and adjust and all from your phone.

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[Duff]

Interesting topic, something I thought about looking into for the 417 .. then after a Google I can't tell if they're supposed to come as standard in the VFC version. Can anyone shed light if they come with one as standard and what Mosfet they have installed?

Literally only wanted it to protect the trigger contacts.

 

[Jedi_Master]

I thought about looking into for the 417 .. then after a Google I can't tell if they're supposed to come as standard in the VFC version. Can anyone shed light if they come with one as standard and what Mosfet they have installed?

You may want to make a new topic for that specific gun.  Bound to be some others who would like to know, and it should be easier to find if a separate. topic.

 

[Duff]

You may want to make a new topic for that specific gun.  Bound to be some others who would like to know, and it should be easier to find if a separate. topic.

Will do, thanks. I've asked the previous owner, assuming he's actually a bit more clued in the history of the gun. I know he used it for maybe two 40 minute skirtmishes from new before selling it to me, so he may or may not know.

 

[Sitting Duck]

Mosfets....

Ask 10 people their views and you will likely get about 5 different recommendations

In reality a mosfet will not change your gun's raw performance much

Usually a stock gun wiring is a mixture of meeeh - half decent - fairly crap

You can install a basic/mid range mosfet using part existing wiring

But often I'd rewire the whole gun when fitting a basic 3034 mosfet

(can be built for about £3~£5 or buy a prebuilt mosfet for £10~£15+)

Even doing a total rewire & mosfet install will only increase rps by about 15%

maybe a smidge more if going absolute nutz 16awg, no breaks, deans blah blah blah

So doesn't boost a stock gun by that much truth be told

Does help a tweaked gun a bit more but still not ultra crazy much above 20%

(unless stock wiring was say completely 18awg with loads of breaks/connections etc...)

A mosfet's primary purpose is reducing the trigger contacts burning out or arcing

If you are running stock gun on 7.4v then likely pulling about 10amps

being that Watts = volts x amps & a fresh lipo is 8.4v

8.4v x 10amps = 84 watts - no biggy

however tweak a gun, faster motor or use 11.1v then $hit happens and watts increase

gun now draws say 15amps to 20 amps

(battery does not change amps but motor/gears/spring do effect the draw in tweaked gun)

7.4v or 8.4v fresh off charge x 15 or 20 amps = 126 to 168 watts

or

11.1v = 12.6v fresh off charge x 10 amps stock = 126 watts

or

12.6v x 15 amps = 189 watts !!!!

tbh drawing much over 100 watts a mosfet should be fitted imho

but mosfets are mainly installed to protect the traditional trigger contacts

Bells & whistles is up to owner

depends on gun & owners budget/wallet blah x 3

still think imho fitting a mofo Titan to most of my cheapo guns

is like installing a fancy cruise control system to a rusty old Mini Metro or Fiat Punto

(two examples depending on your age)

The basic mosfet itself does not provide much if any increase in performance imho

as it is an additional item to be switched on and they will always be delay in milli-seconds

though a heavily carbon deposit switch will have resistance - but a new clean contact switch won't

Still many think the mosfet is the be all & end all that offers the response improvement

(I'm not so convinced as it is an additional device to switch on & complete the circuit)

Most of the response improvement comes from the improvement to the wiring and deans etc....

Should I fit a mosfet to my gun ???

If gun is nigh on stock then no biggy - perhaps just fit deans and leave it

Stock guns on modest 9.6v or 15/20c lipo you will be OK for a good while too

When you start tweaking the gun - changing out motors/gears then yes consider mosfet/rewire etc...

It is all down to the watts (volts x amps) in the end

if you are just nudging sub100w then no biggie

if you are pushing over that then arcing increases at the contacts

higher watts = shorter lifespan of the contacts

and this Watts crap is why some lame guns run OK for a good while on 11.1v

& why other guns (tweaked usually) can have the contacts burn out on 7.4v

all down to the watts (again watts being volts used x amp draw of gun's motor/drive chain)

If you bother to fit a mosfet then look to check and re-do the wiring perhaps if needed

bit like fitting £10 spark plugs x 4 but still using crappy 10 year old stock HT leads in ya car

But it won't be the mosfet that mainly improves response but the more efficient wiring

from 18awg to 16awg & dropping tamiya for deans, as deans without doubt is the best improvement

(bang for ya buck & ease of install etc...)

Deans probably gives ya 8~12% improvement over tamiya

rewiring say a bit less depends on how decent/crap the old wiring was

mosfet - next to FA imho - it is a combination of all other stuff mostly

it is when the contacts burn/arc/build up with carbon that extra resistance appears

and THAT is purpose of the basic mosfet

A v3 mosfet is a walk in the park as you don't need to open up the box to install

a v2 mosfet is a bit of a bitch as wiring layout is all inside and careful planning required

(think it takes a few attempts to grasp neat v2 box rewiring/routing)

New owners with cheap stock gun - just plop on deans and run a bit more juice

9.6v - low burst 11.1v maybe

6-12 months later needing a service TLC then gut the thing and redo the box/gears/motor/mosfet etc...

or

just rip her open now if you are sad and go nutz anyway

but me personally I'd rather not do it all in two or three or four stages or bit by bit on a v2 if possible

The exception to this is you can install a basic £10 mosfet whenever...

and later on you could pi$$ easy replace/upgrade to a mid end programmable mosfet like the Gate WarFet

(the donkey work is already done so most fancy external bells/whistle mosfets can simply drop in)

though some of these fancy programmable mosfets can be like a MENSA test to get your head around

(plus when installing battery ffs don't pull trigger for 5 secs or you enter programme mode and f*ck it up)

As said - you ask 10 people etc....

the mosfet is not the be all & end all either - it's purpose is to protect the switch contacts

it offers little performance but the wiring/deans low resistance is where the improvement really comes from

Even the gun, it isn't the gun but the player's skill that mostly wins the game

but I'm so $hit I need all the help I can get is my lame excuse

To me rewire & mosfet go hand in hand if you can solder (practice & half decent iron/solder etc...)

but to each their own as they say

soz for waffle - just my 2 cents or 2 grand more like

 

[Sitting Duck]

I've got an SVU on the way and was wondering if it was worth putting one in that. Sounds like it will be, but there doesn't seem like much point going for an expensive one - so thank you! You just save me dosh ? 

The other thing to ask is - how easy are they to fit? For someone with zero knowledge of AEG internals, that is....

Seems like a v3 type box - not quite but by that I mean no need to rip open like v2's

v3 type switch & AK type motor cage

so all the basic mosfet install can be done without opening up the box

personally get the thing working nicely and leave it for a while

looking at the sector gear 19 teeth and extra large teeth to spur

looks like ratio could be maybe like them 24~32 sets

where the sector/spur teeth are f*cking massive that requires a half tooth piston

but is a 19 half tooth piston

anyway....

usually them 24~32:1 sets turn SLLLOOOWWWWLLLLYYYY

but pull heavy springs with ease

What the ratio actually is requires counting up all the f*cking teeth and maths bollox

maybe the simple ratio test will still work - can't see why not....

a 12:1 set the bevel turns 4.25 to one sector revolution

4.25 x 3 (the magic number) = 12.75:1 ratio aprox

a std 18 set the bevel turns 6.25 to one sector revolution

4.25 x 3 (the magic number) = 18.75:1 ratio aprox

likely that set in the SVU with jumbo teeth to spur will require say...

8.25 x 3 (the magic number) = 24.75:1 ratio

or

10.25 x 3 (the magic number) = 30.75:1 ratio

something like that between 8~10 turns of bevel gear

meaning it has a bespoke torque gear set

so it is going to run slower to assist pulling mofo spring

(11.1v looks a dead certainty to get some snap out of it)

That said the amp draw shouldn't be mega high on those gears

so a mosfet even on 11.1v may not be a highly urgent one out of the box

(this is a bit of pure guesswork but still feel the amps wouldn't be insane)

I know KoA is rewiring/mosfet but just saying it might not need it straight away

though after 3/6/12 months you could chuck one in easily without needing to open box

as it shares certain characteristics of the v3 switch/motor wiring

so should be quite straight forward if you are getting the Cyma one in the video

 

[sonofsammo]

3 hours ago, Sitting Duck said:



Seems like a v3 type box - not quite but by that I mean no need to rip open like v2's

v3 type switch & AK type motor cage

so all the basic mosfet install can be done without opening up the box

Holy fuckola!
Thanks for the expansive answers! ? 

I'm planning on running it as a DMR, so I'm hoping that the gearbox/battery won't be too stressed when I fix it to single shot.
That video's going to be really useful, so thanks for that again!
Sorry for being dim, but what's KoA ?
 

 

[Sitting Duck]

Holy fuckola!
Thanks for the expansive answers! ? 

I'm planning on running it as a DMR, so I'm hoping that the gearbox/battery won't be too stressed when I fix it to single shot.
That video's going to be really useful, so thanks for that again!
Sorry for being dim, but what's KoA ?
 

Kingdom of Airsoft - clever UK mofo's

 

[Arwen]

Interesting topic! I've been reading up on mosfets again lately as my recce could do with a service.  As it happens... KoA is my local tech, so I will more than likely give it to him to fettle with. My soldering skills suck these days! 

Opinions though, if you don''t care about RoF, is a mosfet still a good thing to have?  ( I think I know the answer but I'm curious on other peoples views)

 

[Adolf Hamster]

Interesting topic! I've been reading up on mosfets again lately as my recce could do with a service.  As it happens... KoA is my local tech, so I will more than likely give it to him to fettle with. My soldering skills suck these days! 

Opinions though, if you don''t care about RoF, is a mosfet still a good thing to have?  ( I think I know the answer but I'm curious on other peoples views)

imo yes, for protection of both contacts and battery, and being a bit snappier. mosfet/lipo/deans combo is the go-to starting point for any gun i own, currently the only non-mosfet gun i have is the vsr

 

[Arwen]

Cheers, my recce does have a fuse before the battery, so is slightly protected, and it runs on 7.4 lipo's already. However I've not converted it to deans, and as it is now misfiring occasionally it's about time it gets a look over by someone more competent than me! ? 

 

[Adolf Hamster]

Cheers, my recce does have a fuse before the battery, so is slightly protected, and it runs on 7.4 lipo's already. However I've not converted it to deans, and as it is now misfiring occasionally it's about time it gets a look over by someone more competent than me! ? 

fuse will protect against over-current, but lipo's generally have pretty high current capacity. i was meaning more low voltage protection, stop you from over-discharging the battery.

you can do the same thing by making sure you change the moment the rate of fire starts dropping, although i'd be hesitant to lend someone a gun that didn't have protection.

 

[Sitting Duck]

Interesting topic! I've been reading up on mosfets again lately as my recce could do with a service.  As it happens... KoA is my local tech, so I will more than likely give it to him to fettle with. My soldering skills suck these days! 

Opinions though, if you don''t care about RoF, is a mosfet still a good thing to have?  ( I think I know the answer but I'm curious on other peoples views)

If you are tweaking your gun or giving it a good service

then me personally rewire & mosfet especially if the stock wire is a bit crap

Soldering - honestly it is a case of just having a go

most of which is down to a half decent iron and DECENT solder

perhaps a bit of flux - you can buy a soldering kit off fleabay/amazon for £15~£20

even if you don't fit mod chips to psx/xbox like I did many many moons ago

and I wrecked a couple - the aeg's are a walk in the park than pulling off tiny smd components from pcb

(f*ck I had some real nightmares I'll admit)

How much would somebody at a shop charge to fit a few deans to some batteries & ya gun ???

It is all a case of a bit of practice really and nothing on these toy guns is THAT HARD really

For intricate work you want like a 25w iron with fine tip

for deans a bit more beef say 50w and fatter tip

https://www.amazon.co.uk/INTEY-Soldering-Electronics-Temperature-Adjustable/dp/B075S345MB/ref=sr_1_11?s=diy&ie=UTF8&qid=1536582176&sr=1-11&keywords=soldering+kit

now that has a variable temp so dial it down for switch/mosfet wiring

dial it up with a fatter tip for changing connectors on batteries etc....

dunno if solder is any good, might wish to buy better stuff and maybe flux paste/pen

that was my biggest mistake trying to use crap from poundland and a mig welder for close pcb work

(fine tip 20/25w max for modding consoles and decent low temp solder with flux and kynar wire)

piece of pi$$ when you got the right tools - I learnt the hard way

That is my take on this - or failing that tag a m8 who CAN SOLDER if you can't

Even if you are on a budget if you got a few m8's that between them can buy some bits

if you get into toy gun crap and one of you have access to say:

good b6 type charger

soldering kit

dremel (maybe) or a set of files (large/small)

mini vice maybe

chrono - c'mon you are going to need one at some point if you tear guns apart

probably other stuff but just giving a rough guide of bits that come in handy

you won't use these all the time but worth grabbing some stuff between you & your mates

they will come in handy for many other things.....

well maybe not the chrono if you give up peew peew but the other stuff will come in handy I'm sure

Or failing that find a m8 who is into or his dad is into electronics/engineering that can solder

ask him nicely to re-do the gun with deans maybe - even if keeping ya gun stock

replace your old 8.4v nimahs when they die with lipo's blah blah blah