TECH: Using a second MOSFET to protect your fire modes

Still trying to get my head around how all this is wired/connected. I have made a diagram of how I think it goes, is this correct?


I’m pre coffee but that looks about right

Bit of a mindFk to draw isn’t it.

I’d not run your harness exactly as drawn though.

Minimise cables and maximise flexibility so you can work on bits without upsetting other bits

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OK, my weak point is,…well everything! I’ll give it a go and if it doesn’t work, :face_with_symbols_over_mouth: :face_with_symbols_over_mouth: :face_with_symbols_over_mouth: :face_with_symbols_over_mouth: :sob: :sob: :sob: :sob: then I salvage what I can and try to make a sandwich out of shit.

So, electronics, I follow 85% then someone asks a question, 80%, a good answer, 90%, someone contradicts, 60%, you get the picture, right.!

What relay are we talking about here? size, part number etc…pictures, I need pictures? I may be old but I can still see! Before someone was talking about T238 active brakes (of which I have one) and he says there are two types pos and neg trigger connections WTF?

Why get so complex, I understand what you guys are doing and why. Saves buying either new electrics or new blaster…cool, I can run with this. But then changing polarities on products, this I do not follow…


In this adventure is about keeping the sexy fire modes that the ordinary stock board provides

Whilst handling the current associated with modified blasters

Parts list is easy up top

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My bad, I broke the golden rule… spoke without looking first. I thought the hand-drawn diagram was the start. How embarrassing… :persevere:

Thanks H, Good to know, and appreciate your pre coffee patience.

its a long long way to scroll up eh…

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That was me, there is 2 different variants of the T238 active brake module. One of which is the same as the easyfet where you just run 2 wires from the trigger switch back to the t238 FET, the other you loop off the the positive wire to one side of the trigger switch and the other side of the switch goes back to the T238 FET trigger terminal. Majority of blasters are negative switched so you would have to rewire your switch either way anyway, no one is reversing polarities of anything in ether case, just wiring it up in a configuration different from factory. drawings for both variants can be found online.

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Good to hear! Do I need the Bestar Br-1050 reed relay (struggling to find it on jaycar) or will this work the same:
The specs seem similar from what I can see.

That is the one listed :rofl:

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Why the relay?

Motor is -ve switched

MOSFET is *be switched

Relay does the conversion

Plus…I like the electrical insulation it provides the primary fet


@zeHamish, I have fuses, connecty things for them. I have relays and two easyfets on the way.
Fuse instal is no worries, inline on battery +.
My question is, can this be made to run without the easyfet in the QBZ which only has one fire mode, (full auto.) without a secondary MOSFET? Will the relay serve a useful purpose in this one or should I just fit the active brake into it.

The others, AUG has 3 fire mode select and the M4 will have T238 V1.41 programmable MOSFET installed. They will be wired as per your plan.

Cheers, Jeff

If you swapped in a big enough relay yes. The easyFet just faster and smaller

This solution is more about keeping those fire control boards safe from crazy motor draw current.

You get no control of run on if a relay is used but besides being slower (appreciably? NFI) in electrics switching it’ll do a good job

I don’t think this has any fire control boards at all, just the three switches, trigger, mag feed and safety switch. Plus that rude thing already in there as cruise called it and you didn’t GAF… :thinking: :joy:, So, is it worth doing anything other than a fuse???

That wiring harness is really something.

I can’t call it a harness in good conscience…it’s more like a waterfall

Trigger, mag feed & safety?

Wire it like a gen8 with a fet / relay.

If I’ve understood your schmozzle correctly

I am in the process of tidying that up now. I can’t even work on it looking like it does. Trigger is obvious, behind is the safety lockout switch and above is the mag prime, but its fallen out of position. Should I leave that factory thingy on the silver line in it?

Trim it back, heatshrink it.

Cabling should come up nice

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You need that thingy.
Otherwise it will shoot
every time you prime.
It rhymes. :rofl:


Thanks, guys, guess I better keep that then, eh? :hugs:

because of the design, I figured out why there is so much wire, shorten it and you tangle with the barrel and the strange way the opposite side has different stampings in it. :thinking: So I have done some suave management of lead-outs and pending MOSFET it will all be applied to the LHS front lower with some form of adhesiveness. Of the 43cm barrel, only the T piece and the 2.5cm at the front are supported, so some judicial EPA will be cut neatly in the centre and some tape wrapped around it to help take the slack.

Really keen to see this when it’s done

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