Touch switch question

[Commie]

I've read a few very old threads about it here. I'm assuming the laws of physics hasn't changed much in 2 years. Even found a very spiffy schematic from Scubadatdan here: http://www.e-cigarette-forum.com/fo...one-know-how-make-touch-contact-switch-2.html

Few questions about it though:
1. Can I reverse the polarity of the battery in that schematic? As in, can one of my touch points be simple ground (metal body of the mod)?
2. If the battery is a standard 4.2-3.7 volt, how much will this switch lower my voltage, if any?

Edit: oh-oh-oh! Found a simpler schematic here schalter227bhf6xek.jpg auf fotos-hochladen.net
Will this work with a 3.7 battery? It was originally referenced from a 5Volt thread

 

[Java_Az]

You cant just switch the battery around , If you want the touch switch to work off a ground you would need to use a P channel mosfet rather then a N channel. P channel switches a positive voltage and turns on when a negative voltage is applied to the gate. A N channel mosfet switches a Negative voltage and turns on when a Positive voltage is applied to the gate.

Mosfets actually have less resistance when on, then manual switches. Voltage drop would be in the Hundredths of a volt so not even noticeable.

the IRL3103 will work just fine with a 3.7 volt battery

 

[Berylanna]

I can't figure out how to use a mosfet (IRL3103) when the whole flashlight is aluminum and the 510 connection is guaranteed grounded because it touches the flashlight frame. The schematics show the atty getting positive from the switch and negative from the IRL3103. But for 3.6v, I thought the IRL3103 is all that is available?

Looks like I need to find a small 3-amp switch that doesn't fall apart and save the IRL3103's for wooden mods?

 

[Java_Az]

I can't figure out how to use a mosfet (IRL3103) when the whole flashlight is aluminum and the 510 connection is guaranteed grounded because it touches the flashlight frame. The schematics show the atty getting positive from the switch and negative from the IRL3103. But for 3.6v, I thought the IRL3103 is all that is available?

Looks like I need to find a small 3-amp switch that doesn't fall apart and save the IRL3103's for wooden mods?

In this case you could flip the battery around and run the positive threw the case. Center post on the atomizer connector would be ground. You would wire it up exactly like the schematics in the first post.

If it was me i would just slap a P channel mosfet in it then you wouldnt have to flip the battery and can keep the case a ground. There are tons of mosfets that will work for our application the irl3103 is just the tip of the iceberg.

 

[astartes]

Or try imrl6401 mosfet: https://www.dropbox.com/s/gle91ivmuzvvq45/fet6401SensorTaster.png
(is very tiny and not easy too solder)

I have this mosfet in my mod: https://www.dropbox.com/sh/g30yzx7swvkfwmz/o13LI-WgtB

 

[BikerBob]

In this case you could flip the battery around and run the positive threw the case. Center post on the atomizer connector would be ground. You would wire it up exactly like the schematics in the first post.

If it was me i would just slap a P channel mosfet in it then you wouldnt have to flip the battery and can keep the case a ground. There are tons of mosfets that will work for our application the irl3103 is just the tip of the iceberg.

Does is really matter if the case/ground reference is connected to the positive or negative? I don't think the atty or ejuices would care one way or the other. "Ground" being the negative end of the battery is just a "convenience" for engineering, so all voltages can be referenced to that as a "zero voltage" point. I could pick "2volts above the battery's negative end" to be ground--then I'd have to calculate knowing one end of the battery is at +2volt, and the other at -2volt. This starts to make the math messy.
The only issue I could see here, is the connector to the battery--will it still make proper connection to the other end of the battery?

 

[Berylanna]

Does is really matter if the case/ground reference is connected to the positive or negative? I don't think the atty or ejuices would care one way or the other. "Ground" being the negative end of the battery is just a "convenience" for engineering, so all voltages can be referenced to that as a "zero voltage" point. I could pick "2volts above the battery's negative end" to be ground--then I'd have to calculate knowing one end of the battery is at +2volt, and the other at -2volt. This starts to make the math messy.
The only issue I could see here, is the connector to the battery--will it still make proper connection to the other end of the battery?

It does not matter at all -- unless you are using a mosfet that cares.

I am. Unless I just find another switch and forget the mosfet. I might well do that.