Touch switch question...

[Quigsworth]

Tomcatt linked me this a while ago but I was saving it for a mod that I thought suited a touch switch (just about finished).

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I'm using a IRLU3114ZPBF and I have it working using tiny brass rounded end nails (temporary) about 2mm apart...it seems I have to have a pretty wet finger to get it to fire completely...what r value should I be tweeking to make it...I guess "more" sensitive...thanks in advance for any help.

 

[breaktru]

I usually start with 10 Meg, and work up if need be. Some as high as 100 Meg. Note: make sure you also try it w/ a load as I found sometimes you may have to increase the size of the resistor.

 

[slimest]

Agree. The issue seems to be because of 2-4 meg resistor. Another way - increase surface of the contacts. Say, use a circular (coaxial) structure.

 

[Quigsworth]

I was wondering that too, I have a 1M between the gate and source now and thought, at least of what I understand to be the concept anyway, that that's a pretty high drain to overcome just by using the continuity of my finger, which is why I actually have a 680 ohm (maybe that's part of my problem too?) in place of the 1K...as far as the contact points, I hear ya on the coaxial idea slim...I was thinking of using a carto connector (center post filled and finished with silver solder). Increased surface area and a .5mm gap could only help things.

one of these days I'm going to build a mod using gear I understand, use a Telemecanique motor starter, a 100A contactor and a Seimens variable speed drive for my regulator...you'll all be in trouble then...thanks for the quick answers guys, appreciate it...

 

[breaktru]

I use a 14ga-12ga Solid copper wire in center

 

[TomCatt]

I used the rounded head brass nails for contacts and have 4 10M resistors in series between gate and source. There was some discussion on this circuit around the 1K resistor probably not being needed. I have the 1K resistor in my circuit.

 

[Quigsworth]

Thanks Tomcatt, any thought about tossing in a 2.5 - 50K trimmer between the S and G?...up here in BC Canada our humidity is all over the map, might be kinda cool if you could tweek it on the fly if you will...

 

[Quigsworth]

Ok, this is driving me nuts, unless the humidity of my skin is like 2% I can't get this thing to fire without first licking my finger, good thing I'm not a sewage treatment plant worker...also, the fet just doesn't seem to saturate and fully switch, I'll get 4.07v at first then it slowly starts to drop...after about a 5 second fire I'm lucky if I've got 2.5 - 3V, I've checked about everything, fresh batts, 47K between gate and source, 680 ohm between gate and outer ring of an atty connector, batt v to the center...could I be using the wrong fet? IRLU3114ZPBF, do these die by degree and I have a bad one?, anyone have any ideas before I just rip it out and chalk it to the fact I'm a complete failure in life

 

[breaktru]

47k between gate and source? why did you go lower? your making it worst. Try starting a 10 meg on go higher if needed.

 

[jhonutz]

you may use from mosfet with VGSthreshold = 0.4 ..1V for mod 3.7V batt`s- switch -atty.this IRLU3114ZPBF it`s good only to pull down a on/off pin from an stepdown IC

 

[breaktru]

I've used the 3114 w/ single battery boost mods w/ no problems. Turns on w/ FULL voltage and Zero off.

 

[Quigsworth]

Ok. it seems I got at least close to the right r values but, I give up, a touch switch (for my skill level anyway) is proving far too flaky, I can get a positive "on/off" no problem but I can't seem to get a stable "on" voltage...seems the only way I can get a full v fire is if I first dip my finger in salt water, meh, maybe I'll have better luck in a non-conductive enclosure, maybe it's the fet I chose, maybe I just suck with anything beyond a batt/switch/atty

 

[jhonutz]

I've used the 3114 w/ single battery boost mods w/ no problems. Turns on w/ FULL voltage and Zero off.

Belive me..A single batt`s connected to atty it`s not like booster, have drop down voltage on that mosfet, with atty connected. To minimize this dropout voltage need to use a mosfet with lower VGSthreshold, in that way the mosfet will be totaly open in load.

 

[Quigsworth]

I think (and my head hurts from thinking), jhonutz is right, I think the spec's on this fet aren't quite what I need for a touch...tact switch works great...that's ok, I've submerged it in hot glue in my G9 mod never to be seen again and when the fet (and mod) dies I'm tossing it in the trash, it's a piece of poo anyway...silver lining, I think my electronics trouble shooting skills got better, thanks guys for your replies

 

[jhonutz]

if you command a fet like this, with finger, it`s have short circuit protection .

 

[notsmoking]

Hey Quigs... I am not sure if this will help you or not .... but take a look.... its a good touch switch video.
E-cig Touch Switch HOW TO - YouTube

 

[Quigsworth]

Thanks notsmoking...I saw that vid and was thinking "ok, I'm doing that, like wtf!"

anyway...fedex guy was just here!, I've got a couple 3103's to play with now (only about 5x the size of the 3114's)...but I've decided, this will not beat me, besides seems all the "big boy modders" here have done TS's...I wanna be a big boy too...

but if I do fail, my stainless steel clicky Mamu switches where in the same box...man, those are nice, like $8 ea. nice

 

[notsmoking]

Yea , I have been thinking about it too... but recently I have been trying the rebuilding of atty's and will go back to giving it a try.

 

[Quigsworth]

I'm about done re-building atty's...that's some fiddley work...I just went and bought a GG Odysseus, now that's a piece of gear...I will say though, I did the ce2 mod and it's not too much a PITA and works pretty good too if you get the right kanthal/wick combo...I found the 36 awg kanthal on the ce2's gives a bit better result than the 32 awg, but that kind of thing is pretty subjective. The wick on the other hand, if you can lay your hands on some xc116 ceramic...tough to beat, but I haven't done SS mesh yet, a lot of guys swear by it...

 

[notsmoking]

Right now I have the 32 awg kenthal and the 400 mesh ss The mesh does seem better but I still have work to do to get it to be better. But I am doing ok at it. I also have been getting alot of my info from Scubadan.... damn that guy is good. I did buty some of the ceramic paste and will see what I can do with that. When you get that touch switch working ..... don't forget to post it... after all the frustration.... you need to show it off... Good luck...