The Mosfet Thread

[Clot]

To add to my little problem up high!

 

I have solved this, and the gun is running great now...... The mosfet was FINE. And thus the last two were prob ok aswell........ The motor comm had became charred and caked in carbon, and thus wasnt delivering power!

A quick sand down later. zoooooooom!!

 

[Shriven]

Right, looking at ways to build an SR25alike @ 500 fps ( locked to semi) and looked at the ARES M110. Very nice looking guns, I can get mids for them, and apparently very accurate indeed, out of the box.

However, I'd like to lock it to semi via a mosfet... how on earth can I do this when the gun uses a microswitch to fire?

[Private_Pyle]

Just a quick point on the active braking. The TM PSG1 has this even though at the end of a complete cycle the spring should be fully compressed. Found this out when looking to wire in a mosfet into the PSG to improve the trigger response, although this was improved slightly by a LIPO alone.

Think a mosfet/active braking will be of much greater use when there is a lot of semi being used (CQB or real cap mags) and with higher rating batteries 9.6 /11.1

[CrazyApe]

Hey there

Before I start I'll just say that as far as it goes I know very little about mosfets so don't blame me for my ignorance

Anyway. I just wanted to know if the three shot burst mosfets are easily produced/modified to fit an AEG or is it far cheaper/more practical to by them off the shelf and if so from where?

[RSM]

Right, looking at ways to build an SR25alike @ 500 fps ( locked to semi) and looked at the ARES M110. Very nice looking guns, I can get mids for them, and apparently very accurate indeed, out of the box.

However, I'd like to lock it to semi via a mosfet... how on earth can I do this when the gun uses a microswitch to fire?

 

 

Semi locked trigger master fet, even without a cut off lever they only allow the gears to cycle once.

[Unbad-N]

Will any mosfets on this page: http://www.futurlec.com/TransMosIRF.shtml

Be suitable for airsoft? I'm looking for both n-channel and p-channel mosfets.

[tosuzu]

Dov4000 or anyone tried the one mosfet thing?

[tosuzu]

Can't edit but was meaning to say resistor instead of mosfet.

[gzus11]

aye. it works perfectly for me, but others have had trouble. most likely due to some other cause.

[Docv400]

Yes, I've done half a dozen or so so far, no problems.

This is with a single 'N'-channel MOSFET set-up.

[Unbad-N]

I really need to know where i can buy mosfets that are usable for airsoft.

I've found this site:http://www.futurlec.com/TransMosIRF.shtml

But i don't know if any of those mosfets ca be used in airsoft.

Cloud anyone please help me?

[gzus11]

cant help you find anyhting in your country,

 

but what you want is the lowest possible internal resistance,

eg IRF1404PbF spec sheets says 0.004 ohm highest current,

202Amps, and a voltage that suits the battery you have again

spec sheet says 40v and a gate voltage of +-20v

 

look for something like that one you should be fine,

also p chips for the braking have similar specs

[Unbad-N]

Thanks for the info, but i still need a webpage to order from.

Unless there are any uasble mosfets here: http://www.futurlec.com/TransMosIRF.shtml

[Docv400]

If you cant find the 1404 series, then the 1405 that's listed in that link (21st from top) looks to be pretty close in spec...

IRF1405 Specs...

[Unbad-N]

If you cant find the 1404 series, then the 1405 that's listed in that link (21st from top) looks to be pretty close in spec...

IRF1405 Specs...

 

Thanks, i will try that one out.

What about p-channel mosfets then?

[Powerslave]

Hi,

 

Does anyone know where I can get a IRL1404Z (N Channel) Mosfet and a SPP80P06P (P Channel) Mosfet? I'm trying to make an AB mosfet like that made my Doubletap in the guide on page 5. If these can't be got does anyone know if the fet mentioned in the above posts would be good for the N channel and just search for a P channel one with similar specs?

 

Cheers,

 

mike

 

EDIT - Just found this on RS is it pretty much the same as what I was describing? (Sorry to be a bit noob about this but I haven't done anything electronic since school)

 

Also have found the P channel fet I was after.

[Can]

Top one you linked What you need to be looking at is the manufacturers part number ie IRL1404ZPBF for the item linked

 

Though some where in this guide there is a link to a N channel mosfet which is slightly better speced can't remember it of the top of my head though.

[gzus11]

try and get the irF1404, think its better.

[Powerslave]

I was comparing them on RS (Here and Here) and the specs seem to be pretty similar a few numbers either side usually. The irf1404 seems to have a miniscule amount more resistance.

 

I've ordered a couple of the irl1404zpbf's already so I'll give them a try first I reckon and see what happens.

 

Thanks for the advice though

 

mike

[gzus11]

that seems fine, i would say go for the lower resistance, and highest dissipation,

which that one is. so good choice.

 

i think that is different from the ones i compared last time when the irf came out

on top maybe thay have just been improved since i got the last batch. good luck

with the build, doubletaps guide seems to be the easiest to follow/buld though i

found some simpler ways to put it together and reduc ethe size slightly, think its

mentioned in the "how to build" sticky.

 

if you need any help give a shout.

 

ps i still have had no problems operating a single resistor in the circuit, i chose

1k ohm to give approx 0.001Amps in the trigger wires. ther ehas been some

discussion in here, but i feel as both chips have a common signal pin it would be

almost impossible to have both activated unless there was overlap in the threshold

gate voltages. still its a common pin that gets +v when triggered and 0v when

not.

[Powerslave]

Thanks I hope it goes well. Doubletaps guide is indeed one of the easiest to follow and I think I've seen some methods in the other thread for compacting it like trimming down some of the components.

 

I will be back if it goes wrong!

 

Cheers,

 

mike

[gzus11]

good job, id say follow the guide but put the chips the oter way round so the brake is on top,

if that makes sense.

[bjorn]

I have a small but expensive problem here:

 

JG G36, upgraded internals, M150 spring. Gearbox is shimmed good and works wonderfully.

Using 7.4v 1800mah 40c lipo and a regular IRL1404 mosfet with 10 Kohm and 100 ohm resistors.

 

Problem: I keep on frying the mosfets after x rounds fired in semi and full auto bursts.

First mosfet went really hot and melted internally after about 300 rounds. Second one went the same way after only 100 rounds fired. Max lenght of bursts were around 10 rounds no more.

 

So now I soldered two IRL1404 mosfets together, still using 1pcs 10 Kohm and 1pcs 100 ohm resistors. So far so good after 100 rounds or so. They do not get so hot anymore and everything seems to be fine, as said, so far so good.

 

The gearbox does not take enourmous amounts of energy and is shimmed ok. Might the problem be the fact that I ordered the IRL1404 mosfets from Ebay, HK seller. Maybe they are fake and the stats are a lot lower then advertised?

 

Mosfets are:

IRL 1404

5B 2D

IR 847P

 

Question 1: Can anyone tell me what might the problem be most likely? I have done working mosfets before.

Question 2: Should I add another 100 Ohm resistor parallel to the one I am using right now? E.G. 2 mosfets should have 2 gate resistors?

 

Anything else I might have missed?

 

Bjorn

[Powerslave]

Quick update I have now constructed 2 of Doubletaps AB mosfets and tested one of them (very briefly) with no gearbox just straight to a spare motor and it seemed to work just fine. Can't test under load yet as I need a tiny tiny balance lead adaptor (which is currently being sorted out by the nice people at Tantronics). I will be back to tell what happens.

[Maekl]

Bjorn what motor are you using? It takes quite a bit of force to pull a m150 with a stock ratio gears, and if the motor is weak it will take ridiculous currents and fry the mosfet.