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crackisbad

The Mosfet Thread

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infected.

Do you use PCB for your MOSFET build?

If so, what grade PCB do you use, and what is the current carrying capacity of the tracks/traces?

I was searching for some info and the highest I found listed was 35A :unsure: .

Do you have the motor current running through the tracks, or is it (the PCB) just used as a convenient build platform?

 

I don't use a PCB yet. The guys I know who do, use it more as a build platform except for the extremefire's SW series.

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my my already on page three? :D

 

anywho, i have updated my original first post with both a link for a how-to install and links to websites that sell mosfets. and of course i gave Infected first billing for all his hard work here. Go check it out! ;)

 

Well, i got the echo1 mosfet in yesterday and took some pics for you:

100_1441.jpg

100_1442.jpg

100_1444.jpg

100_1445.jpg

 

i was not very happy with the switch/trigger assembly/thingamajig, or whatever its called, because it wasnt black plastic :P. i never tried it out so i couldnt tell you if it was actually good or not. i re-soldered the wires to my stock G&G (i think) switch/trigger assembly/thingamajig and installed it with that. now, unfortunately as this is my first 'fet, i cant give you any sort of comparisons. and actually due to a brain fart on my part. i installed it on a gun that i just finished building from scratch so i had actually never fired it before without the mosfet installed so i cant tell you a before and after difference either. i can, however, tell you that i am 99.999% sure that is does not have active braking. you cant see it, but the fuse is a 30a. the nice thing about it is that it is not covered in shrinkwrap, but rather in a metal tube that works as a heatsink. all in all, i am really happy with it, i have great trigger response and really great ROF with an M120 and a TM EG700. i tried it with a 8.4v minh mini, 9.6v nimh mini, 7.4v lipo and a 11.1v lipo. with the 11.1v my ROF was just stupid.

 

on that note, is there a MOSFET that you can get that can control your ROF? because im not really into having a gun shoot 25+ rounds a second, i know some people are but thats just not my thing. i'd rather have it around 18 or so and im afraid my 11.1v is just too much.

 

i guess this would be a great mosfet for people that have zero soldering skills and just want to do a straight swap without messing around with any wires

 

on the by; i just bought a standalone inline 20a resettable fuse so will be trying that out on the next mosfet i buy that doesnt have a fuse, or maybe ill use it in one of my nimh batteried guns instead of the stock fuse.

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Thanks for the pics. Yeah, there is no braking feature on that fet. Actually the soldering on that board looks subpar in my book. :(

 

Best thing to do if you want to drop your rof is decrease the battery strength or put in a slower motor. There is 1 or two microcontrolled mosfets out there that have adjustable ROF, but they get pricey and big.

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Hello there, 2 question:

 

Does this work with LiPoly batteries?

How can it fit into a M4 AEG?

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Question about this Active Braking thing - Is there a need for AB? Especially in the UK where power levels are more restricted than in the US? What are the advantages and disadvantages of having AB or not having it?

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Hello there, 2 question:

 

Does this work with LiPoly batteries?

How can it fit into a M4 AEG?

 

Yes, in fact, due to the higher current levels associated with a li-poly it's a near must have.

 

It wires inline with some modification to the stock wiring (although upgraded wiring is recommended). As far as where to put it, that depends on your setup as different m4's will have different places.

 

Hedganian

It's more about the number of cycles than it is the power. Wear on the AR latch, pinion gear, and bevel gear can all be reduced by stopping the motor suddenly instead of allowing it to bounce as it has a tendency to do after each cycle. It becomes more important with high ROF setups as well. I can go more into this later..... (just woke up and the family is waiting on me for breakfast) :P

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Hello there, 2 question:

 

Does this work with LiPoly batteries?

How can it fit into a M4 AEG?

to build off of what infected has said; the mosfet i have pictured above is supposed to be for a M4 wired to the front, i instead used it in a M16 wired to the rear. the one i have pictured is supposed to be used as a straight swap, but i have seen stand alone mosfets that fit in the space of the standard TM M4 fuse holder.

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I'm about to release a set that is built for high current systems (read: magnum motors).

 

YES!

 

I can actually say I've "broken" two of Infected's MOSFET's in high current systems. Infected had blazing fast and extremely helpful customer support for the first borken one, and I fixed the 2nd one on my own.

 

The problem was the same for both cases: I pulled the trigger for a 30-50rnd burst and the black wire that wraps around the side of Infected's MOSFET's broke off from MOSFET terminal due to the solder joint weakening. The first case of the fubar'd MOSFET that black wire contacted one of the other wires and shorted out. The 2nd case it just disconnected, so I just soldered that joint on there more securely. Works great still.

 

The first MOSFET broke on a Magnum setup, the 2nd broke on a PE USA motor.

 

I fully plan on continuing to buy Infected's MOSFET's. I need one for my UMP that's overcycling cause of the 11.1v lipo I stuck in there.

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Okay, so can someone (I'm looking at you, Infected :P ) explain mosfets with resettable fuses to me now, please?

 

Do all 'fets have this feature? It sounds like a good idea, especially since a lot of people seem to be removing fuses from their AEGs to gain a few extra rpm, but I've seen what happens when something locks up and the motor tries to overcome it by drawing more power, I know the fuse in my AUG saved my motor and/or battery at least twice by doing its job and failing before anything else failed, so I'm not convinced that taking the fuse out is a good plan....

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Okay, so can someone (I'm looking at you, Infected :P ) explain mosfets with resettable fuses to me now, please?

 

Do all 'fets have this feature? It sounds like a good idea, especially since a lot of people seem to be removing fuses from their AEGs to gain a few extra rpm, but I've seen what happens when something locks up and the motor tries to overcome it by drawing more power, I know the fuse in my AUG saved my motor and/or battery at least twice by doing its job and failing before anything else failed, so I'm not convinced that taking the fuse out is a good plan....

 

First let's go over some nomenclature problems.

1. What most people are calling a "MOSFET" is actually a cirucit comprised of at least one MOSFET and resistors wired together.

2. MOSFETS are not programmable, nor are they anything more than glorified high current switches (which is a good thing). They have the ability to carry large currents, and switch them on or off very fast.

 

Let us look at self resetting fuses.

These have upsides and down side. I personally don't care to include them in my MOSFETS for one reason. Most novice airsoft players don't know that if there is a problem with your gun you need to stop shooting it immediately. If you don't... you'll just break more stuff than already is broken. Self resetting fuses (an addon to a MOSFET Circuit), will trip when the current reaches beyond a certain threshold, and after a moment (when the heat dissipates), it will reset allowing you to shoot again. This is where the ignorance of a novice creates problems.

Thought process:

1. Gun stopped working... what's going on? <pulls trigger several times>

2. Fidgets with stuff

3. Pulls trigger again and the gun is working. Must be okay now.

4. Shoots and breaks more junk in the gearbox, and the gun is now dead in the water.

5. Stupid gun.

 

By using fuses that blow, the player is going to have to get another fuse. Hopefully this makes them take more time to fix whatever is wrong. Now for more advanced players and airsoft mechanics, we are more likely to recognize there is a problem and fix it before messing with the gun further. For them, this is an advantage as they don't have to replace the fuse all the time if there is a problem.

 

Taking out a fuse / bypassing a fuse is NOT a good idea, and I do not recomend it to anyone. Am I guilty of it... yeah. But remember, do as I say not as I do ;).

 

If you're running a lipo battery you seriously risk your gun and your battery and your own personal health by not having a fuse in there.

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If you're running a lipo battery you seriously risk your gun and your battery and your own personal health by not having a fuse in there.

 

 

:yikes:

 

 

My MG36 has no fuse, no mosfet, and a lipo battery, and a high-speed turbo motor, powerful spring, blah, blah.... It's a deathtrap! :(

 

What should I do?

 

 

EDIT: What about having some kind of tripswitch/fuse that needs to be manually reset (rather like the tripsiwtches in a household consumer unit) rather than the standard fuses that must be replaced after they blow? Would that be doable? And it would still mean you'd have to open the weapon up to reset the switch, and thus maybe fix out what's wrong with it in the process.

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I don't mean to sound alarmist or apocolyptic in saying it's dangerous, but there is a chance you could hurt yourself. In the end, a smart player would just toss his gun and watch it burn rather than keep it near him or try to get the battery out.

 

I don't know of a small tripswitch that would fit and work well at the voltages and in the space required.

 

Honestly, I'll probably start offering the resettable fuses soon because so many are asking about them.

 

You could do what I do, get some quick disconnects, and just plug in a regular automotive ATC style fuse (instead of the glass ones). They are thinner and fit more applications, not to mention easy to find.

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Do they blow as quickly, though, in the event of a problem? And how do you know what value to get? I know that the glass fuses I got to replace the broken ones in my upgraded AUG arre 15A quickblow (which is what it says on the packet) - would a normal 15A car fuse be okay to use?

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Do they blow as quickly, though, in the event of a problem? And how do you know what value to get? I know that the glass fuses I got to replace the broken ones in my upgraded AUG arre 15A quickblow (which is what it says on the packet) - would a normal 15A car fuse be okay to use?

A 15A car type should be fine if the gun is good with a 15A glass QB.

 

I don't run fuses, however I am chancing it. & I know it. One day I will pay. Kind of like riding a motorcycle without a lid or shagging a stranger without a condom. I would not recommend any one be as stupid as me. Not that I would ever ride a bike without a condom,,,,,,,,,& a lid ;)

 

Always run an appropriate fuse in any electrical circuit. It's such a simple thing & saves everything from going teets up.

 

 

Greg.

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I may look into this, then, as the car-type fuses are easier to get hold of and more compact than the glass ones.

 

 

My current problem, though, is where to put the battery monitor for my lipo, to warn me of over-discharge. The one I ended up with is pretty big, having two big caps on the back to smooth out PPE and a wacking great buzzer on the front so that I can't fail to notice when it's time to change batteries.... Which unfortunately means that I can't fit it into the foregrip of my G36 along with the battery....

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you could get something like this: Clicky! its small enough that it will probably fit in most battery spaces. i have a couple and it fits even in my SCAR stock

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The one I got is similar to that, but larger, due to the caps on it (which I didn't realise until after I'd got it). What voltage does that one alarm at? 3V?

 

EDIT: The one I've got is here, about halfway down the page, called "Li-Po Battery Management Unit 234"

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Okay, that sounds fine. It's pretty cheap, too, so no issues there.

 

Thinking about it - are those caps even required? Does the Pulse Peak Effect cause any problems in an AEG application as opposed to the RC vehicle applications?

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That's a nice animation, but I wouldn't say it *explained* anything, as such. More like the graphics you'd use on an advert, it tells you that mosfets with AB are good, but doesn't explain why they are good in any meaningful way.

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actually, i think it does.

i dont know if you tried this, but keep clicking a bunch of times on the contacts in stock wiring set up. you will see that the current/ROF continually drops, while the Resistance/Corrosion And Temperature continually increases. whereas with both of the mosfet set ups that doesnt happen and it explains why

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That's a nice animation, but I wouldn't say it *explained* anything, as such. More like the graphics you'd use on an advert, it tells you that mosfets with AB are good, but doesn't explain why they are good in any meaningful way.

 

in a nutshell the AB part of the circuit switches the polarity of the power going to the motor which causes it to stall imediately so there is no overrun on the motor at high voltages (so single shot stays single and not burst) This is perfectly safe as RC model cars have had this and proportional braking with electronic speed controllers for at least a decade.

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