Mosfet help

[The Curse of Millhaven]

There are many, many posts about mosfet switches and such here and it has become a bit bewildering. Can anyone suggest a small, or at least thin, mosfet, transistor, switching regulator or whatever that I can use to put tactile switches into e-pipes? Ideally I would also want to know exactly what resistors I need and anything else I should order at the same time. It should be able to take at least 3 amps and run off of a single 3.7v battery.

Thanks in advance.

 

[Zanderist]

Thing with a solid state switch is that it gets pretty hot. I've used a mosfet switch before in a mod I built, one thing to know about a mosfet(IRF510) is that it will add an esitmated .5 ohms to your circuit.

Now in this link here:
http://rayshobby.blogspot.com/2011/02/mosfet-based-fix-to-makerbot-extruder.html

Shows a simple set up as a mosfet as a switch. Just sub out the motor for the coil.

Only issue I have is I don't know of any thin just large bulky one's such as the IRF510.

 

[Rossum]

Thing with a solid state switch is that it gets pretty hot. I've used a mosfet switch before in a mod I built, one thing to know about a mosfet is that it will add an esitmated .5 ohms to your circuit.

Why? MOSFETs have come a long way since the IRF510 was state-of-the-art many decades ago. Now you can get a 100A rated MOSFET that has an on-resistance less than 5 milliohms.

 

[Zanderist]

Your right just had a look at the mouser website.

MOSFET | Mouser

 

[The Curse of Millhaven]

Thanks. I ordered a couple of irl3103 as that seems to be a very basic unit.

 

[Gummy Bare]

I'm kinda new to it all myself. I've been collecting parts so far, just need to get a few more things and I can make my first few box mods.

I was wondering, what exactly a mosfet chip does and if it causes voltage drop? I know the main reason people use a mosfet (I thing) is that it opens up the range of buttons you can use and makes the whole circuit safer. I don't quite know exactly what it does, or what negative effect it has if any.

:: sent from android with tapatalk ::

 

[WKS01]

Thanks. I ordered a couple of irl3103 as that seems to be a very basic unit.

Looking at the data sheet shows that particular MOSFET will have a fairly high RDS_on. The data sheet is showing 16 milliohms at V_gs=4.5V. With such a high resistance you will not be able to draw to much current as it will heat the MOSFET up too much and fail. The TO220 package can handle around 2 watts without additional heat sinks.

 

[Gummy Bare]

Now you got me questioning mine a little. I haven't made my first box yet, but have been reading as much as I can and collecting the parts.

The Mosfet chips I picked up were the IRLB3034PBF ones. I did so based off of a schematic for a unregulated dual 18650 mosfet box mod I found in a FB box mod group.

Hopfully these can handle what I'm trying to do... Which is make a unregulated box mod that can handle super low ohm vaping.

:: sent from android with tapatalk ::

 

[Trickydick666]

Now you got me questioning mine a little. I haven't made my first box yet, but have been reading as much as I can and collecting the parts.

The Mosfet chips I picked up were the IRLB3034PBF ones. I did so based off of a schematic for a unregulated dual 18650 mosfet box mod I found in a FB box mod group.

Hopfully these can handle what I'm trying to do... Which is make a unregulated box mod that can handle super low ohm vaping.

:: sent from android with tapatalk ::

Are you talking about the diagrams/plans from the "exclusively box mods" group on FB? If so in the files it says the irlb3034pbf MOSFET can setup they give instructions for can handle down to .28ohms

 

[NikZak]

Hey folks, I need some help on MOSFETs, I need one capable of sustaining approx 350 amps... is there any such beast around?

 

[Gummy Bare]

Are you talking about the diagrams/plans from the "exclusively box mods" group on FB? If so in the files it says the irlb3034pbf MOSFET can setup they give instructions for can handle down to .28ohms

I don't think so, it was the one made by ThunderHead. It's a jpeg file that lists the items needed and shows the wiring diagram. It didn't say anything about the level of ohms it could handle.... At least not on the file to download.

:: sent from android with tapatalk ::

 

[Trickydick666]

I don't think so, it was the one made by ThunderHead. It's a jpeg file that lists the items needed and shows the wiring diagram. It didn't say anything about the level of ohms it could handle.... At least not on the file to download.

:: sent from android with tapatalk ::

Ok, haven't checked that one out yet, if you do go on there check out the group lots of diagrams,parts lists and helpful people

 

[NikZak]

Hey folks, I need some help on MOSFETs, I need one capable of sustaining approx 350 amps... is there any such beast around?

Not sure if anyone saw this, maybe it got lost at the bottom of the last page, can anyone help?

 

[The Curse of Millhaven]

Looking at the data sheet shows that particular MOSFET will have a fairly high RDS_on. The data sheet is showing 16 milliohms at V_gs=4.5V. With such a high resistance you will not be able to draw to much current as it will heat the MOSFET up too much and fail. The TO220 package can handle around 2 watts without additional heat sinks.

I do not know a ton about how mosfets work. RDSon is Greek to me. This is a mosfet that is commonly used for box mods when someone wants a touch switch. I now have two nice e-pipes operating with these, one mine and one for a friend. They vape like champs, indistinguishable in power from mech mods. They get warm under heavy chain vaping, but not hot. I don't know what to tell you except that they work really well.

That said, if anyone had another N-channel mosfet that would work and had a smaller profile while still being solderable by a non-professional, I'd be interested.

 

[RickAppling]

Resistance Drain to Source On. The lower the better. The lower it is the more current it can handle.

I do not know a ton about how mosfets work. RDSon is Greek to me. This is a mosfet that is commonly used for box mods when someone wants a touch switch. I now have two nice e-pipes operating with these, one mine and one for a friend. They vape like champs, indistinguishable in power from mech mods. They get warm under heavy chain vaping, but not hot. I don't know what to tell you except that they work really well.

That said, if anyone had another N-channel mosfet that would work and had a smaller profile while still being solderable by a non-professional, I'd be interested.

 

[RickAppling]

Why!!! Are you sure you didn't misplace a decimal point? That would around 1.5KW, or about 2HP. I do not know if there is a single device that can handle that kind of power. But several devices can be used in parallel. But it would require a LARGE heatsink. And certainly would not be hand held. To give you some idea of how much power that is. A Segway uses two 2HP motors

Hey folks, I need some help on MOSFETs, I need one capable of sustaining approx 350 amps... is there any such beast around?

 

[NikZak]

I'm making a device capable of that kind of power, the decimal place isn't missing and yes it will be a kilowatt capable device

also, based on my calculations, it will be handheld (it'll be a large box mod basically)

 

[WKS01]

I do not know a ton about how mosfets work. RDSon is Greek to me. This is a mosfet that is commonly used for box mods when someone wants a touch switch. I now have two nice e-pipes operating with these, one mine and one for a friend. They vape like champs, indistinguishable in power from mech mods. They get warm under heavy chain vaping, but not hot. I don't know what to tell you except that they work really well.

That said, if anyone had another N-channel mosfet that would work and had a smaller profile while still being solderable by a non-professional, I'd be interested.

The issue is the MOSFET package can only dissipate so much heat without an additional heat sink. If you heat the package up too much, you can damage the MOSFET and it will no longer correctly work (if lucky it will remain open, if not it will be stuck closed). Though the particular MOSFET mentioned will work it is important to properly select the parts for the conditions the part will see.

I'm making a device capable of that kind of power, the decimal place isn't missing and yes it will be a kilowatt capable device

also, based on my calculations, it will be handheld (it'll be a large box mod basically)

Is this a single user device?

 

[NikZak]

Is this a single user device?

That's the plan, it will be both portable and reasonably lightweight. planned box dimensions are the size of a large thick pocketbook style wallet, about 7"x 3" x 1" plus atomizer

any suggestions for a mosfet capable of handling that kind of power? I can find 100W mosfets but having trouble with something around the 3-400W mark

 

[WKS01]

That's the plan, it will be both portable and reasonably lightweight. planned box dimensions are the size of a large thick pocketbook style wallet, about 7"x 3" x 1" plus atomizer

any suggestions for a mosfet capable of handling that kind of power? I can find 100W mosfets but having trouble with something around the 3-400W mark

There is more to the design of something like an unregulated box mod than merely the wattage the MOSFET can handle. Every characteristic for a MOSFET will change with change in temperature, drain current, drain-source voltage, power dissipation, drain leakage current,drain-source on-state resistance, etc. The data sheets from the manufacturer are full of tables you use to determine the characteristics under various conditions. What also worries me is that you state you cannot find a MOSFET rated between 300-400 watts, but a quick search yields a number of results that can dissipate 300W+. When playing with the currents and wattages you are talking about you must know what you are doing. If looking at a MOSFET data sheet confuses you, I would say you should not be attempting what you are doing.