Found this link with some interesting stuff if your interested.
Capacitance / Touch Switch Circuits free electronic circuit links
Capacitance / Touch Switch Circuits free electronic circuit links
Touch Switch building info.
- Thread starter nicotime
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Nicotime
Nice timing I was wanting to make a transistor switch,. A touch switch would be a good part to add on that .
Thanks
Dan
Nice timing I was wanting to make a transistor switch,. A touch switch would be a good part to add on that .
Thanks
Dan
Ha...you get one made make us a how-to....I'm tired of hot chips of ceramic stuff popping out when I solder a bunch of stuff together and plug it in.
Ignore the PIC & beating heart references. 
I'm using 2 1.5 AAAs in a box as power. The transistor is a C9105 13(or B) 438 PNP. I used the same value resistors & a white LED as the output. This works, but-
When I touch both wires(with my fingers), I'm getting .24v across the led. If I touch both wires & the negative side of the led(with my other hand), I'm getting .4v. If I touch the 2 wires to each other, I'm getting 2.68v. The output of the battery box is 2.8v.
I realize the transistor can only use what is sent to it, barely any with a touch, almost full voltage when I touch wire to wire.
What is needed to get the full voltage to the output by touching the wires. Or, what kind of switch can be used that will be triggered as the PIC is, with a very small amount of voltage.
It's been too long since I was in the electronic books.
I'm using 2 1.5 AAAs in a box as power. The transistor is a C9105 13(or B) 438 PNP. I used the same value resistors & a white LED as the output. This works, but-
When I touch both wires(with my fingers), I'm getting .24v across the led. If I touch both wires & the negative side of the led(with my other hand), I'm getting .4v. If I touch the 2 wires to each other, I'm getting 2.68v. The output of the battery box is 2.8v.
I realize the transistor can only use what is sent to it, barely any with a touch, almost full voltage when I touch wire to wire.
What is needed to get the full voltage to the output by touching the wires. Or, what kind of switch can be used that will be triggered as the PIC is, with a very small amount of voltage.
It's been too long since I was in the electronic books.
One thing to watch in the design of a touch switch is device dissipation if it is allowed to operate in the linear conduction range between off and on. When off, current is not flowing and the device dissipates nothing. When turned full on, the device resistance is minimum and the device dissipates the current conducted (squared) times the device on resistance. (2 amps through a MOSFET with on resistance of 0.02 ohms = 0.08 watts dissipated by the MOSFET).
If the device is turned partly on then dissipation can be much higher. If device is partly on, i.e. 1 ohm on resistance and 2 amps is passed then the device will dissipate 4 watts all by itself.
The difference between full on and partly on could fry the transistor (or FET).
Two stages with the first being a FET logic gate, the second being a FET switch would eliminate 'partly on' linear conduction.
Rocket
If the device is turned partly on then dissipation can be much higher. If device is partly on, i.e. 1 ohm on resistance and 2 amps is passed then the device will dissipate 4 watts all by itself.
The difference between full on and partly on could fry the transistor (or FET).
Two stages with the first being a FET logic gate, the second being a FET switch would eliminate 'partly on' linear conduction.
Rocket
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Are we talking about touchpad buttons like on the Saber Touch and Precious? I have both of these mods and the one on the Precious is particularly sensitive. I love that sensitivity but have to be very careful because it turns on all the time accidentally and I have to be very careful where I place it. The Saber Touch is less sensitive but appears to be safer at this time.
Rocketman: Thanks for the explanation. I'll re-read it later in the day. If I get started now, I'll still be working on it when the alarm goes off @ 7am.
jcamacho: I'm wanting a switch similar to the lamps that turn on when you touch them. It would be a small section of the PV that when you touch it(with skin), it powers the PV. With this one, though, when you move your finger, you break the circuit & turn off the power. That circuit I posted works that way, but does not produce enough power. I'm sure Rocketman just explained it to me, but it's to late to try to understand it.
jcamacho: I'm wanting a switch similar to the lamps that turn on when you touch them. It would be a small section of the PV that when you touch it(with skin), it powers the PV. With this one, though, when you move your finger, you break the circuit & turn off the power. That circuit I posted works that way, but does not produce enough power. I'm sure Rocketman just explained it to me, but it's to late to try to understand it.
What we need is someone here to give us the best reliable circuit with part numbers and easy for us non-electro's to build and understand.
Not asking for much huh?
Not asking for much huh?
Pre-soldered also?
I'll have some time this weekend. I've got 2 mods to finish & then work on this.
Today's youth, so lazy.
It all starts with this.
Substituting this mosfet (recommended by cybervex, Mr Bartleby) to handle our current demands.
INTERNATIONAL RECTIFIER|IRF8736TRPBF|Mosfet IC | Newark.com
http://www.irf.com/product-info/datasheets/data/irf8736pbf.pdf
Looks like about $3 in parts.
Note this is switching the NEGATIVE lead so is best suited for box mods.
Here's some diagrams (and more) from the always generous Scubabatdan.
How about this one with a redy to etch PCB layout.
I ain't linking to the entire thread.
Clapper.
Clap on, clap off.
I'm getting ready for vacation and don't have the time to do much modding. I will log in just to see what is going on from time to time. The touch switch idea will be a tough one. Not getting it to work, getting it to work in such a manner than everyone would like it. Too sensitive, not sensitive enough, doesn't work with my old dry fingers but works fine with for the wife. Comes on all by itself when I have it in my pocket and get all sweaty. See, tough to please all. The one point about not allowing operation in the linear zone would not be an issue with PWM. Set an upper pulse width and rate for the type atty you want to use (would be different for LR, Standard, clone, HV attys) and the switching FET is flipping very rapidly from full off to full on. Never pausing in the linear zone. Touch switch combined with PWM would give you pressure sensitive vaping strength, and if set up properly, never too much for your atty. A second touch "Zone" could even be set up as master power. Touch on, touch off. LED for power, LED for vaping power (brighter for more vaping power). Maybe all of this can be made into a FRU (Field Replaceable Unit) in maybe a 3/4 copper pipe cap. You really have to try and out think everyone to come up with something everyone would like. Not simple.
I wouldn't like it if it didn't have an MP3 player also.
Cisco is working on a PWM variable power level MOD. I don't know if it's going to be touch sensitive, pressure variable or not.
Clap on, clap off.
I'm getting ready for vacation and don't have the time to do much modding. I will log in just to see what is going on from time to time. The touch switch idea will be a tough one. Not getting it to work, getting it to work in such a manner than everyone would like it. Too sensitive, not sensitive enough, doesn't work with my old dry fingers but works fine with for the wife. Comes on all by itself when I have it in my pocket and get all sweaty. See, tough to please all. The one point about not allowing operation in the linear zone would not be an issue with PWM. Set an upper pulse width and rate for the type atty you want to use (would be different for LR, Standard, clone, HV attys) and the switching FET is flipping very rapidly from full off to full on. Never pausing in the linear zone. Touch switch combined with PWM would give you pressure sensitive vaping strength, and if set up properly, never too much for your atty. A second touch "Zone" could even be set up as master power. Touch on, touch off. LED for power, LED for vaping power (brighter for more vaping power). Maybe all of this can be made into a FRU (Field Replaceable Unit) in maybe a 3/4 copper pipe cap. You really have to try and out think everyone to come up with something everyone would like. Not simple.
I wouldn't like it if it didn't have an MP3 player also.
Cisco is working on a PWM variable power level MOD. I don't know if it's going to be touch sensitive, pressure variable or not.
Today's youth, so lazy.
It all starts with this.
Heyyy...I'm only gonna be 50 in two months...give me a break....I got a lot to learn yet!
Thats the one I was looking at too...now where to get that finger??
I was also wondering if juice residue would trigger these?
I find it amazing that touch switches are still being discussed. In my experimentg I found that they work just fine if your skin is moist. The last two pics that WillyB post will work.
Pretty much the same circuit I used except I added the USB charging to the circuit.
Cheers
Pretty much the same circuit I used except I added the USB charging to the circuit.
Cheers
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