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Topic: Is there an "reverse" mosfet? (Read 509 times) previous topic - next topic

raschemmel

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Technically yes there is, there N-Channel and P-Channel MOSFETs available in the voltage range you are looking at. 
I am guessing you want to switch the high side. The source would be on the +220 and the gate is referenced to that, The gate has a Vgs rating in the range of 15V.  That is telling you if the voltage difference between the gate and source exceeds this value the FET will be damaged and eventually fail. An opto isolator would make the interface safer and a lot easier then doing high voltage with semiconductors. Remember if it is a 220V mains lines that is a nominal RMS voltage. Do the math and you will be very tight with a 400V mosfet.  The gate drive circuit will be a bit difficult if isolation is needed.  If it is the AC mains consider a triack. I would suggest getting a good book on basic electronics and learn what parts are for and what they are called.
All true, except for the fact that OP wants to use 230vac TO SWITCH 5.5Vdc.

Paul__B


electronicsnoob

XY problem strikes yet again!
No it is not an XY problem! I just wanted to know if there exist something like a "reverse" mosfet! Nothing else! I said 5.5V and 230V because they are standard voltages used for arduino Projects! I thought such a mosfet would be useful for some of my future projects.

TheMemberFormerlyKnownAsAWOL

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I said 5.5V and 230V because they are standard voltages used for arduino Projects!
You really are earning that nick.

Please, get some education before you hurt yourself.
Please don't PM technical questions - post them on the forum, then everyone benefits/suffers equally

raschemmel

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I said 5.5V and 230V because they are standard voltages used for arduino Projects! 
Since when is 230V a standard voltage used with arduino projects ?
Where on Earth did you get that idea from ?


electronicsnoob

Since when is 230V a standard voltage used with arduino projects ?
Where on Earth did you get that idea from ?


I live in Germany. The Voltage in our sockets, lamps, dishwasher, etc. is 230V!!! If I want to Switch something like the light in my room with Arduino, I have to use 230V! And there are many arduino projects that switch things.

JCA34F

Why not save yourself and every one else a lot of time by just telling us what you are trying to do?

raschemmel

If there were a country that used 480vac,
would that make it a commonly used voltage for arduinos ?
They make solid state relays for that.

DVDdoug

#23
Nov 16, 2019, 01:01 am Last Edit: Nov 16, 2019, 01:02 am by DVDdoug
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No it is not an XY problem! I just wanted to know if there exist something like a "reverse" mosfet! Nothing else! I said 5.5V and 230V because they are standard voltages used for arduino Projects!
You CAN use a MOSFET or transistor to control a low voltage (low current) with a high voltage (or high-current) but it's just not clear what you're trying to do and it seems like you're about to do something that's dangerous to you, dangerous to your Arduino, and dangerous your computer (if your computer's USB is connected to something that's connected to dangerous voltages).

BTW - MOSFETs can be used as part of a circuit to control AC, but a single MOSFET doesn't work on AC.   And going either way and even if the AC is rectified, the Arduino should be electrically isolated from the power line!

I gave you 3 possibilities and I recommended a that you use a relay.   You can take it from there or give us some more details and ask more questions.

MarkT

In theory you could have a MOSFET with a thicker gate oxide layer that would take 230V to switch it on(*).  It would still be a MOSFET, nothing reverse about it.  You can use a MOSFET rated at 10V gate drive to switch 0.1V, 1V, 100V (if sufficiently rated), there's nothing special about the output voltage having to be larger than the gate drive.

(*) Noone would ever use one.  Optoisolated gate drivers are available for this sort of application.

[ BTW a bridge rectifier on 230Vac gives 325Vdc - AC voltages are quoted as rms. ]
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

Paul__B

No it is not an XY problem!
But it is.  :smiley-lol:

You have invented a term, "reverse mosfet".  That suggests a way of doing something but is essentially meaningless as we do not know what it is you really want to do and on that hangs all the detail - because there are obviously different approaches for different needs.

The important question which you have persistently failed to address is the need for isolation.  If you need isolation, then an optocoupler is the answer and we move on to how this will be connected, whether it must reflect the AC polarity inversions or give a smoothed response and if so, with what attack and persistence.

If OTOH, you do not require isolation, then there still remains questions of which elements are common and what polarity is what.

The implication that there is a single component or a single process and thus a single answer is clearly time-wasting, that is the XY problem.  Failure to pose a genuine usage case is nothing more than trolling - as we now realise.  We are no longer answering you as it is pointless, but for the benefit of any innocent who stumbles across this with a genuine need.  :smiley-roll-sweat:

TomGeorge

I could use an bridge rectifier and I have 230V DC. That is no Problem.
Might I suggest you use a small transformer to drop the 230Vac to 6V, then rectify and then switch a MOSFET.
This way your DC and controller circuit will be ISOLATED for the 230Vac MAINS.
230Vac to 6Vac low power transformers are easy to find online or at your local electronics store (if you are fortunate to have one).
Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

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