The... Mosfet...

[SupplyDaddy]

While I haven't seen the Mosfet being taken overboard here, I am wondering what opinion others have about "having" to use a mosfet for unregulated mods they make.

Seriously, it's crazy in the two box mod groups I'm in on Facebook. People get banned for disagreeing with others about having a mosfet in every single build...

Personally, I build my unregulated devices for low power use. 18 gauge wire, 3 amp, 250 volt switches are the norm for me.. No mosfet. I have built one device to use a mosfet because I wanted to use a tactile switch in it and the mosfet allowed me to do that. Even then, it's a little 14500 single battery mod that has no advantage of using a mosfet other than being able to use that tac switch.

What are your opinions on using this item?

 

[twgbonehead]

There is one, and IMHO one reason to use a MOSFET. And depending on what you're doing it's either an unequivocal Yes or No.

The MOSFET is used to turn a switch with a low ampere rating into a switch with a high-amp rating. If you're turning on and off high currents, then it's pretty much a requirement. Even at medium currents (in the >1A range) a MOSFET helps tremendously, since it doesn't suffer from issues such as arcing, that a mechanical switch would.

Off-the-shelf switches that handle current in the amps range tend to be very large, and often have large "throw" forces required. Most mech mods avoid this by integrating the "switch" into the physical design of the mod (i.e. a bottom-button design that pushes a contact with a large surface area directly onto one end of the battery).

A MOSFET will let you use pretty much any switch (even a touch-switch, which is just a couple of connections to the fet) to fire very large currents (or small currents).

And your 3-amp 250-volt switch is NOT rated at 3A DC, I will bet. That's an AC rating, and the DC rating is usually much less (and/or unknown). I PROMISE you that your switch will not handle 250-Volt 3A DC (but that's not really the relevant question, since you're unlikely to be running your coils at 250V). What current can your switch break reliably at X volts DC? (you can't infer it at all from the AC specs. and it degrades over time, particularly if it's running anywhere near it's capacity).

You can, by the way, significantly improve the ratings of a switch by putting an appropriate capacitor across it.

Geez, I thought this was going to be a simple answer.....

I certainly would have no problem recommending in almost any design that a MOSFET be used. (Not in a true mech, usually) They're cheap and provide a lot of benefits.

 

[Norrin]

Never used one as I find it just as easy to make a proper mech switch, but if I wanted to use a bought switch in yet another hammond box mod then I would use one. The thing about using the wrong switch as opposed to other things is that it's likely to just break with no real danger to the user, but it will probably tell you that it's unsuitable before hand by trying to burn your finger.