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crackisbad

The Mosfet Thread

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Not strictly on topic, but I figure the electrical wizards lurking in this thread are likely to know the answer to the question:

 

How does the fire selector on a typical AEG (I know the AUG is diffent with the two-stage trigger) affect the resistance of the motor circuit? Does the motor current pass through the fire selector (I assume it does) and is there another way of making the fire selector work that won't route large amounts of current through the fire selector, in the same was as the mosfet diverts current around the trigger contacts?

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No matter what you have to have a switch somewhere in the system. You could make it out of better quality parts, or incorporate a MOSFET into a PCB with a push button switch where the trigger acts like a lever to hit the button, but either way you're looking at using a msofet to actually drive the power to the motor.

 

The selector plate contacts and trigger switches are the largest inhibitors of current in the stock design.

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Infected, just got the new mosfet yesterday. Im just curious to what that substance at ends are. Looks like glue or some kind of silicon. Im guessing its to make it more water resistant?

 

Anyway thanks!

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Infected, just got the new mosfet yesterday. Im just curious to what that substance at ends are. Looks like glue or some kind of silicon. Im guessing its to make it more water resistant?

 

Anyway thanks!

 

Some people asked me to make them more water resistant, so I have started to use a sealant till I'm out of my current batch of heat shrink. I'll switch later to a heat shrink with sealant in it. I don't know if people are swimming with these or what. I've played in the rain for quite sometime before and never had a problem with them unsealed (just covered with heat shrink).

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Hey do you know where to find an AB MOSFET guide for V7 or just a universal guide? (not biased towards V2)

 

thanks, oggy

 

Ask and ye shall receive:

 

M14-Wiring-with-MOSFET.jpg

 

Now this is for the TM v7. The CYMA is more like a standard v2 since it doesn't have the additional wiring at the safety switch.

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Random mosfet question that doesn't necessarily need to be answered.

 

So I just killed 2 mosfets in my gun, not exactly sure how, but the end result leaves the mosfet in an always on type state (delivering the batteries voltage) but no current. When the trigger is pulled, it acts sort of like an inverter and the voltage on the output drops to zero.

 

Yes I have the right type of mosfet because they were both working fine until I killed them (not sure how?).

 

Anyone have any clue as to what would cause such an incident?

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Random mosfet question that doesn't necessarily need to be answered.

 

So I just killed 2 mosfets in my gun, not exactly sure how, but the end result leaves the mosfet in an always on type state (delivering the batteries voltage) but no current. When the trigger is pulled, it acts sort of like an inverter and the voltage on the output drops to zero.

 

Yes I have the right type of mosfet because they were both working fine until I killed them (not sure how?).

 

Anyone have any clue as to what would cause such an incident?

 

So it's acting like it's on when you're not pulling the trigger, but when you pull the trigger it acts like it's off?

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Err, first of all we're talking about a mosfet I already fried, and yes and no. Since there's no current, I only detect the voltage with a multimeter.

 

So long as there's no current involved, that's basically it. I figure if I tell you what it looks like when it's dead, someone would be able to tell me how I killed it (so I can prevent it from happening in the future).

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Err, first of all we're talking about a mosfet I already fried, and yes and no. Since there's no current, I only detect the voltage with a multimeter.

 

So long as there's no current involved, that's basically it. I figure if I tell you what it looks like when it's dead, someone would be able to tell me how I killed it (so I can prevent it from happening in the future).

 

First of all you can't have voltage without current. If the current = 0 then the voltage =0. Voltage = current x Resistance.

 

I was just trying to figure out what it was doing so I can figure out why it failed. You might have just had a resistor go bad, or short. That could cause the problem you were seeing.

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How does the fire selector on a typical AEG (I know the AUG is diffent with the two-stage trigger) affect the resistance of the motor circuit? Does the motor current pass through the fire selector (I assume it does) and is there another way of making the fire selector work that won't route large amounts of current through the fire selector, in the same was as the mosfet diverts current around the trigger contacts?

The motor current passes through the selector contacts and the trigger contacts, in series.

When fitting a MOSFET you just use this circuit to 'trigger' it, by running one of the two wires (from the trigger contact block) to the +ve supply from the battery, and the other to the MOSFET's 'Gate' pin.

So the current to the motor only passes through the MOSFET.

The original wires can be replaced by much thinner ones as the current needed to trigger the MOSFET is very low.

A lot of the clone AEGs come with either the selector contact strips soldered together, or removed completely, so they have just the trigger contacts.

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So a more technical kind of question to owners of AB mosfets in SA sniper guns.

 

Does AB really mean a difference in FPS consistency? If so then are there any hard evidence of it?

 

I plan on building a G&P MK14 Proto based SA sniper in the future, but I cant decide if I will go for a simple mosfet or an AB mosfet.

In theory it should not matter much, if at all since the tapet plate, nozzle, gears etc will still travel the same way as always? With AB mosfet they will simply stop at the same place every single shot. Will that really matter in FPS results and e.g. feeding?

 

 

 

Hope to get some clear answers on this subject.

 

B.

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sIn running a high voltage (11.1v lipo), SA only dmr, it helps to avoid over spinning of the sector gear. Over spinning the sector gear can cause the tappet plate to move back a bit and alter the bb's position in the hop unit. I run an AB mosfet in my DMR.

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Should not the bb already have left the barrel when tapet plate and nozzle start to move back again with the sector gear?

 

B.

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Maybe you do have a point.

 

So to be sure and exact - with the AB mosfet the sector gear, tapet plate and nozzle will always stop at the exact moment when the nozzle and tapet plate are in most forward position and they have sealed the hopup rubber completely?

 

If anybody with AB mofet is willing to do a quick test then fire in semi a few times and try to blow air into the inner barrel from the top end. If the nozzle stops when it is completely forward then the theory is correct and AB mosfet can and probably will make a difference.

 

B.

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Maybe you do have a point.

 

So to be sure and exact - with the AB mosfet the sector gear, tapet plate and nozzle will always stop at the exact moment when the nozzle and tapet plate are in most forward position and they have sealed the hopup rubber completely?

 

If anybody with AB mofet is willing to do a quick test then fire in semi a few times and try to blow air into the inner barrel from the top end. If the nozzle stops when it is completely forward then the theory is correct and AB mosfet can and probably will make a difference.

 

B.

 

since it's not a timing device it might not be perfect every time, but it will be more consistent if you're running a high voltage setup. The only way to achieve perfection would be to do what SYSTEMA has done with the Revolution gearboxes by putting an optical sensor on the sector gear to know it's position.

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Depending on who makes it and thereby what specific parts and circuit they use it will stop differently but consistenly

The ones i have tried enough energy is sucked out the geartrain and more importantly the motor coils that it wont have enough energy to start compressing the spring again. Puts it at a nice resting position for another shot.

 

 

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