Adding a Voltmeter to an Unregulated Mechanical Mod (single 18650)

[Gabriel Chavez]

Hey guys! Been cruising the forums for a few months now, learning all I can. Finally decided to get rid of that pesky 5 post restriction so I could ask some more advanced questions ^_^

So I have a mechanical mod right now (basically a metal tube with a button and a rda).
I am a tinkerer, and broke as a joke (pharmacy student -_-), so I'm hoping to be able to spend a few bucks to mod what I have, rather than building a box mod from the ground up.
Now, to what I have planned...

I want to add a small 2-wire voltmeter and a switch of some sort to activate it when I want. (I'll be designing a custom enclosure to attach to the outside of the mech mod, but that's not what I'm here to ask about)

Now my problem is, I cannot find a switch that is rated to handle the 6-8A that my battery puts out on a continuous basis. (never really measured it at 8 watts, just leaving room for error) (not sure if I need to worry about peak watt ratings or not) The only ones that can handle that much current are massive and not useable for what I want to do. I can't use a resistor, as that causes a voltage and amperage drop, and would result in an inaccurate reading on the voltmeter.

I have seen many different wiring diagrams here using a MOSFET along with dual batteries and a circuit board. I have yet to find anything that shows an unregulated mod with a single 18650 battery and a voltmeter though. Can you guys please help me out?


I have read more than one page trying to understand how a MOSFET works, in the hopes that I could just design a wiring scheme myself. However I just can't get it at the moment. I'm going to blame stress and trying to learn too many things at once, but maybe I'm just dense

 

[Gabriel Chavez]

Just to be clear, here is the ultra simplistic diagram of my unregulated mod

 

[Visus]

The voltmeter does not have the atomizer amperage flowing thru it, very minute amperage, lol unless you wire it in series then it would blow up before any reading anyway.

You can use a tact switch, any switch, just connect it to your battery +- put any switch on either one of the legs from the voltmeter and your good to go..

A main switch is a total different ballgame and yes that needs to be rated for the task of handling the atomizer amperage..

This image will self destruct in 3 days

 

[Gabriel Chavez]

Thanks for responding.
I'm a dummy. I should have done some basic research on voltmeters before opening my mouth.

Voltmeters have such high internal resistance that the current they draw from the battery should be minimal. So I should be able to use any switch then. Thank you for making me think a little rather than just calling me out on the level of derp that I exhibited.

I think your image already self-destructed by the way But if its just a picture of a tact switch I understand

So I'm just gonna wire it like this. Hopefully I am thinking correctly, but please say something if I am not.




DIsregard the second picture that is below... I posted before thinking it though, and can't figure out how to delete posts or pictures.

 

[Visus]

Those bastiges said it would in 3 days it was up the 1st day I used the free edit screencapture program and their free webpage service that supposedly holds the image for 3 days which is kinda cool.


Your drawing is fine either way one you gotta press the fire button and have an atomizer on to view volts drop at the atty the other is on when tact switch is on and will show both: batt voltage no atomizer and drop at the atomizer..

Not a dummy you asked before kapow. V meters use a voltage divider in them and yes by resistance turns amps very low up to a certain rating. But not if you connect it in series then kapow at very low amps lol..

 

[DaveSignal]

The way I have done it on the two G boxes I have so far built is by connecting the voltmeter positive to the switch wire that runs into the gate on the mosfet, then negative connected to the negative battery terminal (or source pin on the mosfet). The voltmeter then turns on when the switch is pressed.

 

[Gabriel Chavez]

Thanks for the encouragement and clarification Visus.
Dave, that looks to be how most of the mosfet diagrams have it set up. I just don't completely understand the way a mosfet works to be honest, as much as I have tried to research them. I don't think I need a mosfet though since I am just using a single battery. Thanks for the tip though!

 

[drmarble]

You only need a mosfet if you are planning on using coils under 1.0 ohms. You can avoid the mosfet if you machine your own switch like Rob does for the Reos. A normal switch and a sub ohm build is a fire hazard with a subohm build. Four amps can easily weld an underrated switch into the on position.