MOSFET question

[blobface]

From my brief understanding of what mosfets are (even though I've been using them for a while, I've never tried to understand in depth what they do) basically transistors that allow current to flow through it when there's a much smaller voltage flowing into a separate "gate", so basically it almost act as a door that only opens to allow power through when a little bit of power is supplied into opening the door from a separate source. Is there a type of mosfet that one could buy easily that does the opposite? Which means, the door is closed when voltage is supplied, so the default stage is always ON, and with voltage into the gate, it becomes an insulator.

The reason why I'm asking is that I was wondering if I could do a simple AEG mod (body mod and mag mod), so that everytime a gun runs out of ammo, a small copper lever is then pushed up by the BB feeder, and the copper completes a circuits inside the gun, which triggers the mosfet into blocking any power into the motor.

[richardy]

Re: MOSFET question

Why be physical about it a better solution would be a magnet in the bit which pokes up out of the mag when empty and a hall affect sensor in the mag well. Program a pic to shut of the circuit when it reaches a certain amount on the sensor.

Being a sopmod owner its not something im in a hurry to do though...

/puts feet up.

[blobface]

Re: MOSFET question

Why be physical about it a better solution would be a magnet in the bit which pokes up out of the mag when empty and a hall affect sensor in the mag well. Program a pic to shut of the circuit when it reaches a certain amount on the sensor.

Being a sopmod owner its not something im in a hurry to do though...

/puts feet up.

That's a really good idea, good one, I can easily hook it up with an arduino nano. I'm a SOPMOD owner too :P but it's just want to do it to my other AEGs too, recently been looking into crap loads of Israeli stuff so I got myself a set of gear from ***CENSORED***, so gonna get me a tavor to go with it... but I just hate the gun firing blanks, even though I can tell by feel and sound... it just feels.. silly.

BTW I'm currently working on putting a micro button into the sopmod gearbox, working out the distance so that I can make sure the bolt stop / semi continues to work... and I'm storing the AB mosfet in the buffer tube (I don't use the recoil feature anymore)

[richardy]

Re: MOSFET question

man not using the recoil just upsets me i love that feature. Its all part in parcel with the package. No mater how much i might like another design of aeg i simply cant ever use one now which isnt recoil. Its like when i ditched the 2 litre for a money saving 1.4 eco cheap tax thingy... no mater what i tell my self .. somethings always missing from it everytime i drive it.. i think they call it fun.

AWS are working on bring a sopmod raptor fet out soon. When it comes to next gen recoils, i have to think about the bigger picture. Doing a small mod solution will be perfect for you (or me back in the day) but wont help the hundreads of owners out there wanting a mosfet in there sopmod, who dont want to do excess work, or chop something or remove the recoil or rewire to the front just for a mosfet. Whether its fitting a lipo or mosfets inside the gun, theres simply more players who want a simple no fuss solution and to keep the gun standard than to work on it them selves and mod the gun. Infact id say ontop of that theres even more players that NEED that simple no hassle no fuss solution. Hopefully AWS will come through for us with there next gen version and everyones got a simple mosfet solution to fit into there sopmods.

[blobface]

Re: MOSFET question

Yeah man I know what you mean, every time I put the recoil unit back in it reminds me how awesome my gun used to be, but then since I play pretty much strictly on semi.. the battery doesn't last very long... even with 3000 mah lipo, and right now I'm using a traditional stock and the TRX handguard... there's just no other space I could think of for the mosfet, not to mention me front wiring it to a leaf type 1100 mah battery.. Like you said, if the raptor fet is going to be out, it'd be perfect for me since most of the stuff's in the gearbox.

[richardy]

Re: MOSFET question

Imax b6 charger and incar adaptor.. charge your batterys during diner break.

Or

High torque gears maybe and bearings from prometheus. The double torque versions maybe in an effort to take some load off it and a reshim. Although the hornbill gears and lonex are popular due to there price they offer no really torque up benifits verse standard, just stronger. The seigeteks are also an option although current versions have an issue with the cut off lobe and need modding.

I ran a 3200mah lipo pack for an entire days play, i then lent it to a friend who i assumed would have charged it but didnt, he then played a days play. It came back pretty flat but none the less and great example of what it should be doing maybe. I used a socom for a period and it used 1600mah lipos.. id use 1 for about half a day and before i let it even get a chance to get low i switched out to another 1600mah due tot he low cost of lipos i didnt mind having 4 but only ever used 2 unless playing 24hrs.

The 7.4v 1100mah i put on a sopmod which was 450 fps and it wouldnt turn it over just not enough guts in the battery. Just another example but as you can see youve got this sort of limited area which we can exsist with batterys which actually power our sopmods sufficently. This is why dispite the price the promy gears are a pretty attractive option that and not running your sopmod at 450 fps :P

[blobface]

Re: MOSFET question

Oh yeah? I got the Echigoya torque motor, which I think did jack all, looks like promy gear is an inevitable step, although, I think I'm still going to mosfet it, so 11.1v could be my friend to overcome that issue. I made my sopmod into a DMR at some point, it was doing 430 fps :P This platform is pretty accurate, I was able to hit a 5p everytime I wanted to at 15m indoor no wind, speaking of DMR, I asked you this question on a different thread, but I've lost track of it, I bought some real steel 20rd magpul mags, have you seen anyone mod a next-gen mag insert into a 20rd magpul mag? (lots of cutting and sticking to ensure the feed tubes line up I'd imagine).

[No1_sonuk]

Re: MOSFET question

From my brief understanding of what mosfets are (even though I've been using them for a while, I've never tried to understand in depth what they do) basically transistors that allow current to flow through it when there's a much smaller voltage flowing into a separate "gate", so basically it almost act as a door that only opens to allow power through when a little bit of power is supplied into opening the door from a separate source.

The analogy I usually use is a flexible pipe that is crimped by voltage to block the flow.

Is there a type of mosfet that one could buy easily that does the opposite? Which means, the door is closed when voltage is supplied, so the default stage is always ON, and with voltage into the gate, it becomes an insulator.

Sort of.
The usual MOSFET used is an "N-type". This is the one that conducts when a positive voltage (with reference to the Source pin) is applied to the gate. Grounding the Gate will turn it off.
The "P-type" MOSFET requires a negative voltage (WRT the Source) to conduct. Grounding the Gate will turn it on (P-types are connected the opposite way round to N-types).

However, the best option for what you describe would be to use an N-type MOSFET with a simple bipolar inverter driving it.
That way you'll get the definite on/off signal the MOSFET needs.

As for your magazine cutoff idea:
You could make it mechanical by using a switch to cut off the trigger circuit.
However, the aforementioned Hall effect idea would be much easier to set up in the gun, and far less work in the mags.
Plus if you put the magnet in the right place, the mags could be used in any other gun without problems.

It's an idea I may use myself.

[richardy]

Re: MOSFET question

Hmm was gunna get a load of those echi motors not great hearing you didn't see much improvment on average no load draw from aftermarket verse tm is about 1amp verses 1.2 in hi torque.

I believe theres a guide some where probably the big Sopmod thread on armies for fitting the sopmOd mag inserts into the real steel magpul casings

[blobface]

Re: MOSFET question

Yeah there is one on Echigoya, with images and stuff, but that's a standard size insert, looking to see if someone's done a 20rd version.