please help with copper pipe mod

[gixer]

Hi,
I'm currently putting together a copper pipe mod. I am planning on using a small tactile switch. I'll be using a transistor to turn the atty on and off. This one was recommended by a guy at the local electronics store. 2n3904

I got it to work using this set up.

This seems like it would work in a box mod, but I don't know how it would be set up in a copper pipe where the ground is the body. Anyone have any ideas? Any help would be swell.
Cheers,

 

[Rocketman]

I'll check the specs but I think the 2N3904 is a "small signal" transistor.
I don't think it will handle atty current and if it does the dissipation (voltage drop times current) will probably fry it.
Back in a bit.
Rocket

Yep,
it won't work. Nice photo though.

http://2n3904.com/
Was that the local Radio Shack? Ask him to recommend a cell phone plan instead of electronic components.

 

[crazyhorse]

You don't need an electrical switch or wires in a copper pipe. You can use a mechanical switch. Search the battery mod forum on the subject of copper and you can find models for 14500 and 18650 batteries.

 

[petercro]

Yep,
it won't work. Nice photo though.

2n3904 - Information, Specifications, and Datasheet
Was that the local Radio Shack? Ask him to recommend a cell phone plan instead of electronic components.

After that recommendation, I would rather ask my 9 year old daughter.

 

[Rocketman]

After that recommendation, I would rather ask my 9 year old daughter.

You need to teach her a little about electronics and take her to Radio Shack and have her embarrass the clerks there (in front of customers).

I used to when I was 9 or 10.

 

[gixer]

Hi Guys,
Thanks for the replies. Your help is greatly appreciated. Would anyone know how I would set this up? I would really like to keep a low profile switch in there. Here's what it looks like so far. It's a tactile switch.

Thanks again,

 

[Rocketman]

You can search for a jFET circuit that was posted for a dual voltage MOD. Since you intend to only use 3.7 volts the circuit would only need one FET.
The advantage/purpose of the FET over a linear junction transistor is low on resistance and thus less energy lost in the electronics and more available to the atty.

You could epoxy the FET to the copper cap and get more than enough heat sinking to protect the device.

Connector mounting:
You can press a battery connector or adapter into a nickle (needs a hole of course) then bring the connector through a hole in the front cap. Makes for a strong front end.

 

[gixer]

I've looked up the fet like you said, and it looks like there are a few options.
Si2333DS
Si2315BDS
CSD16325Q5C
IRLU3114ZPBF

Thanks again rocketman. You've been super helpful.
Cheers,

EDIT:
I looked into it more, and it looks like these would need to be on ground in between the battery and atomizer. I guess it still wouldn't work in the pipe mod using the body as ground. I think I'll just give up and find a new switch.

 

[Rocketman]

gixer,

The schematic shows one terminal of the battery, one terminal of the atty and one terminal of the switch connected together. Atty isn't polarized, switch isn't polarized, battery is.
Just be sure that you insulate the inside surface of the tube when you put the battery in "backwards".

paradigms sometimes have two sides.

 

[JoeMoto]

I've looked up the fet like you said, and it looks like there are a few options.
Si2333DS
Si2315BDS
CSD16325Q5C
IRLU3114ZPBF

Thanks again rocketman. You've been super helpful.
Cheers,

EDIT:
I looked into it more, and it looks like these would need to be on ground in between the battery and atomizer. I guess it still wouldn't work in the pipe mod using the body as ground. I think I'll just give up and find a new switch.

The IRL is the one I use. I used the same small tactile switch you have in my latest mod with a 5v booster. Without a booster the wiring is

Batt- > Source
Batt+ > switch > Gate
Batt+ > Atty+
Drain > Atty-

From what I've read the n-channel mosfets are more desirable because the p-channels require a small voltage to keep them open?

 

[gixer]

Thanks guys,
I never thought of the backwards battery. Thanks rocketman. I have hope again. lol. I will definitely give that a try once I get one of these transistors. I found that the vaprlife mods all use this switch as well, so I guess it is possible.
Cheers,

 

[gixer]

Aarrggh,
I just realized that digikey.ca is shipped from the usa. I think I'll try to find something local. What should I look for on the datasheet when I'm looking for a mosfet that would work with what we're doing?

 

[Rocketman]

There are a few things to look at with FET specifications.
The IRLU3114ZPBF is a MOSFET, N-CH 40V 40A i-pac.
Others with pretty good specs, but I haven't used them are:
IRF7470PBFCT-ND MOSFET N-CH 40V 10A 8-SOIC
IRF7402PBFCT-ND MOSFET N-CH 20V 6.8A 8-SOIC
IRF7455PBFCT-ND MOSFET N-CH 30V 15A 8-SOIC
(just placed order with digikey so we will find out one of these days if they will work )

What you would be looking for in the charts would be an operating condition that closely matched your needs. For example, a V(GS) of less than 3 volts that would give a highly turned on condition, conducting a few amps, and on resistance 10 to 30 milliohms. All of the above should turn on pretty good with a 3.7 volt battery.
Circuit diagram will be just a little different than the jFET circuit shown earlier.
For an N-channel MOSFET the GATE should be pulled low with a 500K to 5M resistor between the Gate and Source. Bringing the Gate to positive through a smaller resistor (5K to 50K) would turn it on.

***Get the battery backwards with one of these power MOSFETs and the internal diode will turn on. No switch required, constant vape. ****
Rocket

 

[gixer]

Thanks rocketman, Hopefully I can find something with similar characteristics.

 

[Rocketman]

been doing even more shopping.
Found some P-channel Mosfets that seem to fit the bill.
Here is one example, an NTGS3136P from On Semiconductor.

a NTR2101P, from On Semi again, but digikey also has it, maybe others.
http://www.onsemi.com/PowerSolutions/parametrics.do?id=809&lctn=home

 

[gixer]

I found a few locally that might work I think not sure.
IRLZ44N
MTD3055VL
RFD16N05L

I couldn't find any appropriate p channel except for the Si2333DS. But it looks really small and hard to solder. The n channel and p channel looks to be wired up differently, just wondering what would be the difference using one or the other in a mod?

 

[Rocketman]

you can pretty much draw out the circuit, MOSFET Drain to atty, atty to battery, battery to MOSFET Source. add in a resistor between the Gate and Source (few 100kohms to a few megohms), Gate to switch, switch to line between the atty and battery.

Assign polarity based on P or N channel. Same circuit, battery polarity needs to match device type. If battery case is not same polarity as mod case then insulate.

Did that make sense? It did at first, now I don't know.

Rocket

 

[Rocketman]

I found a few locally that might work I think not sure.
IRLZ44N
MTD3055VL
RFD16N05L

I couldn't find any appropriate p channel except for the Si2333DS. But it looks really small and hard to solder. The n channel and p channel looks to be wired up differently, just wondering what would be the difference using one or the other in a mod?

On resistance with a 3.7 volt mod (3 volt minimum loaded) is a little high with the MTD3055VL,
the IRLZ44N is a monster, the RFD16N05L would work (I think).
If you could manage the solder job the P channel one you found, Si2333DS, would turn on full at 3 volts GS, real low on resistance, and handle 4 amps.

 

[gixer]

Thanks rocketman. I should be able to pick up the Si2333DS by friday according to the guy at that store. I'm also waiting to clear coat the pipe first. I found some stuff that works well to seal it.
ProtectaClear - Coating Only : Everbrite Coatings, Keep Metals Looking Their Best
It should be in next week, and I can give this a shot.

 

[Rocketman]

lay it out breadboard style before putting everything in the pipe cap. Just in case.