Electrics overhaul

[BIGBC]

Hey peeps

 

Im looking at rewiring a few of my rifles to get rid of obsolete connections/interfaces. I want to get them all on Deans and all batteries on deans with a decent gauge wire and possibly a MOSFET here or there.

 

What gauge wire am I best using? Does the Silicon high temp stuff on Components shop suit?

 

I have got a MOSFET that came unlabelled and without documentation, is there any easy way to tell/test which cables are the positive/negative? (all the wiring coming from it is black).

 

Anything else I should look at upgrading/changing while I'm at it?

[Docv400]

What gauge wire you need will depend on the AEG you're wiring up, and sometimes also on which gearbox version you have.

Something like an M14 has plenty of room for the thickest wires, whereas most AKs, for instance, are pretty tight for space.

14 or 16 gauge is OK for most AEGs, if you have the space, go for 14.

 

In AEGs where the wires are routed through the gearbox ,you can usually re-route them outside, to allow you to use thicker wires, or route one through and one outside.

You'll often need to do a bit of filing/dremelling here and there to make a little extra space as well, particularly inside the grip/motor housing, and/or the motor cage on Version 3s (and others).

 

Bear in mind, the gauge of the wire relates to the copper strands (conductor), and not the overall thickness which includes the insulation, so two 16gauge wires could have different outer diameters, depending on the insulation used.

 

Does the MOSFET have a clear heat-shrink sleeve?

If not, you'll need to carefully cut the sleeve off.

Take a picture of both sides so we can take a look at the layout.

 

It's a good idea to set your Angle of Engagement while the box is apart.

 

 

[BIGBC]

Nice n' informative post, cheers for that.

The MOSFET does not have clear heat shrink on it. And the 'carry' cables are white not black but the 'control' cable is black. One of the white cables has a small section of black heatshrink on it near the end though . . .

Hmm, just taken the heatshrink off and this FET doesnt look like much, just a FET on its own with the cables folded over to give it some meat. Think I've been ripped off in more ways than I originally thought.

The FET has

"F2804L

914P

00 50"

written on it. With the left hand pin soldered to the 'control' cable which has a bridge to the right hand side and the center and right hand pins have 'carry' cables.

 

I'll order some 14 gauge for the M14's/L86 and check the thickness for the M4/M16/SCAR.

 

AoE is something I will have to read into

[Docv400]

That MOSFET is an IRF2804L.

The specs suggest it's more than up to the job...

 

http://www.irf.com/product-info/datasheets/data/irf2804.pdf

It's a little 'over-qualified' if anything, but that won't matter.

If it's just the one 'FET and a resistor (or two), what you have is a basic 'switching' MOSFET unit, with no 'braking' function, which is fine for 95% of AEGs.

Braking set-ups (in my opinion), are only really needed if you have a very high ROF, and you're suffering from 'overspin', where you get more than one shot in semi.

The inertia of the motor and gears causes the gearbox to go through another cycle, even though the semi cut-off has activated.

 

Looking at the 'front' of the MOSFET (where the lettering is) the legs (or pins) are, from left to right;

1. Gate

2. Drain

3. Source

 

The Gate pin is the one you connect the trigger circuit to.

You'll have two wires coming from your trigger block, one needs to be connected to the positive (Red) wire, anywhere between the battery plug and the motor, wherever suits your layout.

The other goes to the Gate pin.

When you pull the trigger, you're supplying battery voltage to the Gate pin to 'trigger' the MOSFET.

The positive wire goes directly from the plug to the motor when you have a MOSFET.

 

The Drain pin is the 'output' from the MOSFET, this is wired to the negative motor terminal.

 

The Source pin is the 'input' to the MOSFET, wire it to the negative terminal of the AEGs connector plug.

 

If you can solder (I'm presuming you can), you can make up your own MOSFET(s), it'll cost you around £5 for a simple switching unit.

The MOSFET 'chip' itself is around £3, and the one resistor you need will be around 10-20p, depending how many you buy and where you get them.

 

I use the IRF1404 series 'FETs.

Usually the IRF1404pbf

 

Check out the MOSFET topic in the 'pinned' section.

MOSFET thread...

 

[BIGBC]

Finally finished my dissertation and have some spare time to finish off the rest of my AEGs.

 

Got some new batteries/connectors and soldering kit in too.

 

Some of my guns are quite shy on battery space and the fuse really makes life awkward. I read around a bit and most people seem to say you should have one but it doesn't really do much unless something goes wrong and you continue to pull the trigger.

Am I safe to remove the fuse from my AEGs? particularly my ICS M4 (stock motor, 1100mAh 7.4v 15C LiPo's).

 

If not, are there any off the shelf low profile fuses suitable for use in an AEG?

[Docv400]

I never bother with a fuse, they're only needed for numpties who keep pulling the trigger when their AEG is making funny noises/'stalling'/smoking etc.

It might be worth keeping in an AEG that has a particularly inaccessible battery, just in case you needed to disconnect in a hurry.

An easily accessible switch fitted in the positive line would be another option.

If you do keep it, you can throw away the casing, and just shrink-wrap the 'C' clips/terminals to the fuse.

Car 'blade' fuses can be tucked in easily, and there are smaller versions too, Google 'Mini Blade Fuse'

 

You don't have to use the holder for them, you can just use the appropriate sized female 'spade' terminals.

 

Also, 15C rating is 'borderline' for AEG use.

1100mAh x 15C gives only a 16.5A discharge rate.

Ideally you want at least 25A for a 'typical' AEG.

[BIGBC]

Thanks for that. I've never been one to keep yanking the trigger when some things wrong. As it is an ICS its easy enough to disengage the piston and pop the gearbox open anyway.

 

I know those batteries are pretty low powered, but they give a better RoF than the 2200mAh 9.6V NimH I was using before I switched the stocks about. What problems could they cause?