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crackisbad

The Mosfet Thread

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No offense, but I think I'll probably shop a little closer to home.

 

None taken.... but know that most of my customers are overseas. Just ask about on the forums and you'll hear all sorts of good stuff about me. But alas... it is your choice. :P

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my latest creation!! haha just a dual-MOSFET

 

9499bc7a57aadf.jpg

 

i have noticed that they tend to get a bit hot when rapid firing more than a few shots quickly, so if i put in two, half the current through each and double the mass/SA for heat dissipation. only good for guns that have the space to take it though, this one is going into my RPK with an M145 running off a 11.1v 2200mah 25C lipol. also made it a little bit prettier with the connectors

 

@ infected: are you able to post which MOSFET you use in yours? if you dont wanna say thats ok.

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Hi all, been lurking a while but have decided to jump in here as mosfets is currently top of my interest list.

To follow on from the post above another couple of places would be

http://unconventional-airsoft.com/store/

or infected's own site

http://infectedairsoft.wordpress.com/item-...eaking-circuit/

 

The problem i see for us UK guys is sourcing the correct mosfet's.

If you happen to live close to an RS components or somethign you are probably ok.

Maplins are woefully understocked in anythign really useful, HUF75337P3 seems to be the only decent mosfet they stock and they dont seem to have any p-mosfets to build an AB for your weapon.

If i were worried about building one i would go ahead and purchase from an established seller, you would then at least get some help with the fitting.

 

Because i'm a geek, i am happy to try myself, i sourced my stuff from Farnells as follows.

IRL1404ZPBF for the N mosfet

IRF4905PBF for the p mosfet

1/2 watt 100 ohm resistor and 1/2 watt 33k ohm resistor

The only kicker is that they have a minimum order of £20 so i plan to build 3 in total, no plans to start selling them though.

Hopefully these are ok to use and i plan to follow the schematics found over at Airsoftmechanics.

 

EDIT: thought i would add that i am fully rewiring my G36 at the same time which to my brain at least makes the job easier to understand.

 

Any opinion on these mosfets? i am pretty sure they are the correct ones to use.

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Carbacca, what the heck is that monster????

 

Seriously, I know you doubled up the mosfets, but I have a few questions.

 

1. is that unit include braking?

2. Did you double both the p and n channel fets?

 

I ask because there is a much more streamlined way of doing it. Plus... there are single fets you can get that will probably yield 2x the current and power handling than 1 of the n channel fets you're using. I'm about to release a set that is built for high current systems (read: magnum motors).

 

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its just a straight 2x MOSFET

 

we are a bit weird here in NZ as we are only allowed semi auto, to fire 10 rounds we need to stop-start the motor 10 times and that creates a huge amount of heat. the single FETs unit i build before for my other guns just heat up like crazy and i dont like how much it heats up by. so i did the double one, reason being half the current, twice the mass for heat dissipation

 

it aint pretty but its going in the stock of the RPK so plenty of space there

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No offense, but I think I'll probably shop a little closer to home.

 

You say that, but, Infected's product is good.

 

I'm in London & have had about 15 of his AB fets over the last few years.

 

Cost is fair & other than one order, which was delayed by customs, the delivery time has been under 2 weeks.

 

As yet, none of his fets have failed me & when the pound was strong they were a bargain. Even with the relatively low exchange rate, they represent good vfm.

 

I do 'electrics' myself & if I thought I could equal his quality, I'd make 'em up myself. I stripped the first one I had off him, to have a look & there is no way I could match is soldering skills. At least not in a cost effective time scale.

 

Not only that, he continues to develop the product, using better materials as they become available. Plus custom wire lengths, appropriate to your requirements.

 

The choice is yours. ;)

 

 

Greg.

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Awww.... thanks guys! :)

 

Carbacca, what are the stats on the fets you're using. Seriously... you should be able to pound off 100 rounds before the fet begins to heat up (in semi). I did it just the other day with one of mine, and the fet wasn't even remotely warm.

 

I'm not about to give out what fets I'm using ;), but I can tell you if what you're using is not suited for the purpose.

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How much do you charge for these 'fets that everyone says are so good? Including shipping to the UK...

 

Are they just general for any AEG, or do you tailor make them to a specific requirement?

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How much do you charge for these 'fets that everyone says are so good? Including shipping to the UK...

 

Are they just general for any AEG, or do you tailor make them to a specific requirement?

 

Pm'd (as this isn't a sale thread and I don't want to get in trouble) :)

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How much do you charge for these 'fets that everyone says are so good? Including shipping to the UK...

 

Gotta say that they are very reasonable, looking forward to a pair through the post anytime :D

 

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is it more important to have high power dissipation or high current?

and how many watts should i am for?

 

i sat on the RS website for about 4 hours running different combinations and pretty arbitarily picked out that one lol

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Rds on is higher than you really want on the 75, even though it's pretty low, you'd like to see it lower. It'll work, but it might not switch fast enough.

 

I can't find a data sheet on the second one.

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i think i have found an even better one

 

STP100NF04

 

mind you there are lots of "good" ones just not a good price, screw paying $20+ for a MOSFET, all the ones i have been looking at are ~$4-5

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i think i have found an even better one

 

STP100NF04

 

mind you there are lots of "good" ones just not a good price, screw paying $20+ for a MOSFET, all the ones i have been looking at are ~$4-5

 

That one is so overpriced for what you're getting. There are less expensive and better performing ones out there ;). It has some good stats, but for the money... it's not worth it. You'd be better off buying an IR MOSFET.

 

Keep in mind, my mosfets include braking (requiring more parts)... sure it doesn't cost me $20 to make them, but I wouldn't do it if I wasn't making money ;).

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funny that it not costing much around here, for what i can get it for, about on par with everything i have seen

 

mind you cos of quantity i am paying RS prices, could be better but then i aint buying hundreds of them

 

that and USD$20 for you add exchange rate becomes NZD$40-50 for me

 

on another note

there was some talk of active breaking creating more stress on the mech/motor itself because of the start-grinds to a halt nature of it; you think there will be any implications for us here who is on semi only? would that make it ever worse for the mech and motor?

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on another note

there was some talk of active breaking creating more stress on the mech/motor itself because of the start-grinds to a halt nature of it; you think there will be any implications for us here who is on semi only? would that make it ever worse for the mech and motor?

 

Honestly, I haven't seen a problem with it. I run with only 85 round midcaps (all my aegs take m4 mags). Being the case, I usually just keep it in semi only. I've never tossed a motor because of the braking feature and my mechbox components are just fine inside.

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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?

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