Increasing trigger response

[KaRcop]

Every time I do something to my SRC G36c, I spend about 5 minutes looking for an allen key I was just using, and it's usually stuck to the pistol grip :P

Hahaha!

In terms of making an AB MOSFET, firstly, I thought you could only get either PNP or NPN transistors? And what extra is needed for AB and how does it wire?

[dope_on_a_rope]

Re: Increasing trigger responsiveness

You don't have a P&N channel FET. You have 2 FETs, one P channel, one N channel. I think the basic idea, is you solder the terminals on them together. Gate to gate, drain to drain, and source to source. But I could well be wrong. Since some company's have made big money on these little things, it's becoming increasingly difficult to find a decent AB wiring diagram...

[dope_on_a_rope]

Re: Increasing trigger responsiveness

Update time.
Turns out I was partly right. I'd like to link you to the origin of this information, to give credit where credit is due, but unfortunately the rules prohibit this. But needless to say, this is not my work.

so an active break unit i have built with n and p channel fets insulated
using a 11Amp polyswitch (pc motherboard resettable fuse)

solder gate and drain of both fets, i install the larger resistor behind
the n channel fet. N channel fet appears to be underneath, but the important thing to note, is the resistor is going from gate to N channel source.

positive comes from battery through thr fuse, connected to the p channel
fet then to the motor, i install the small resistor here.

then attach wires for the switch to the gate and small resistor,
motor negative to nchan fet drain and battery -ve to source.

Not the clearest of explanations admittedly... I'll keep on digging.

Edit: Linky. Best I can do.

[Genista]

Re: Increasing trigger responsiveness

There are plenty of guides online about building AB mosfets. Getting mosfets with decent power ratings is slightly trickier.

The gist of the idea is to present a 'load' to the motor which stops it spinning (or over spinning).

So, when the trigger is pulled and the gate sees a voltage difference both mosfets (p chan and n chan) switch, one on and one off, connecting a neg feed to the motor. The other side of he motor has fixed pos feed.

When the trigger breaks contact both fets switch back connecting pos feeds to both sides of the motor, forcing it to stop.

As far as wiring goes, the fet needs pos and neg feeds from the battery and feeds to both sides of the motor. You can then either have two feeds to the trigger switch or just one and feed the other side from the constant positve side of the motor.

There are various other things going on such as back emf, voltage spikes and over voltage on the gate, which is what the various other components are for.

HTH