Mosfet Question

[Cushak]

It's more of a "Do I got this right?" type thing.

I found a Systema Switch Relay circuit in my tool box, and I decided to find out what it was.





As far as I can tell, it's this:

But that picture indicates I'm missing a wire.

Here's a wiring diagram I made up, based on what I could see on the circuit, and the basic ciruit diagrams on airsoftmechanics.com's MOSFET article.


Resistors:
A is 20,000Ohms
B is 5,200 Ohms
C & D are 2000 Ohms

I may have those number wrong, if they seem unreasonable, I could take a picture of the resistors themselves.

Now with how I'm reading it - from my photo of the underside of the circuit - the wire going off to the left, that should lead to the motor. The wire leading to the right goes to the battery, and the dab of solder on the bottom left hand corner should have a wire coming out of it, going to the trigger contacts, correct?

And than I just wire this circuit into the regular AEG circuit like in this picture, correct as well?


And my final question: Will I even need this? I'll be running a gun on a 9.6V, EG1000 motor, Prometheus Double Torque Up gears, and at most a PGC M130 spring and a Prometheus M120.


Thanks for your help!

[mcguyver]

I think your schematic, as well as the airsoft mechanics is wrong. In MOSFETs, the gate is the middle position, and it shows that on the back of your circuit board as well. Look at the traces for the high-current connections. They are on the outside pf the devices, and a low-current trace is at the center position.

On all the devices I've seen, FETS, BJT, IGBTs, etc, the trigger for the device is in the center position, the input to the device is on the left (if your looking at the markings denoting the device) and the output from the device is on the right. I'm sure there are some exceptions, and an ECG or NTE catalog will tell you which they are.

I would say that the big gob of solder in the corner of the board is where the gate (red wire) was attached.

[Kos-Mos]

I am sorry, but most powerfets are gated on left most pin...

I used a lot of fets from SUM series along with some IRF HEXFETS and they all are GDS pins (gate, drain, source)

There seems to be missing the trigger wire.

The wire on your picture on top, is going to the battery negative
The wire on bottom is going to motor negative
You are missing the wire to the trigger.

I think the wire is supposed to go bottom left, where there is a blob of tin.

You will have to keep the wires to your motor, trigger and battery positive there. Just remove the black wires from your mechbox.

[mcguyver]

Yep, I looked at my book again, and the schematic is correct. But htis is only for MOSFETs, other devices are different.

[Kos-Mos]

If your Systema thing is fried, I should have my V2 ready in a few week, if not a few days.

350A Fet set with active braking and current spike protection. The size of a stock fusebox...