Mosfet for 3.7 volt

[jimR]

I really enjoy the 1AA nicbox I built from mad vapes stock but the 2 amp switch just is to big for the mod. I tried the RS mosfet but it takes 4 volts to fully open the gate and I want to use the tactile switch reliablly.
Are you going to offer something like the IRF8736 Mosfet that is supposed to fully open the gate at 2.3 volts? This is forum info and not verified by me but if I can find something that will work at the lower voltage I will buy it.

 

[hoogie76]

I'd love to carry some once I can find a reliable circuit in a manageable package type. I've been eyeballing these for a while in the 'D' package but not sure if they'll work..

http://www.onsemi.com/pub_link/Collateral/MTD6N20E-D.PDF


Hoog

 

[jimR]

Looked good, but still has the 4.0 volt Max gate opening. Same as the RS IRF510, so I would expect the same results sever current limit.

 

[hoogie76]

Looked good, but still has the 4.0 volt Max gate opening. Same as the RS IRF510, so I would expect the same results sever current limit.

I was thinking a small resistor could keep the gate voltage under 4.0 in the event of a full battery but still stay within range for a low battery. It'd only need a .2 volt drop to stay in range and the gate off is less than a protected li-ion batt cutoff. I like the package style so I've been staring at it for a while..

Unfortunately, last time I took electronics, nand gates were the big new item.

Hoog

 

[h8isgr8]

Jim, how good are your soldering skills?

TI has a line of MOSFETs with perfect specs for low voltage/high-current apps.......

Power Management - MOSFET - CSD16325Q5C - TI.com

For the voltage and current that you would use them at (combined with the short ON time of this app), you might be able to get away without any heatsinking. You would just need to solder on a few connecting wires.

 

[jimR]

Jim, how good are your soldering skills?

TI has a line of MOSFETs with perfect specs for low voltage/high-current apps.......

Power Management - MOSFET - CSD16325Q5C - TI.com

For the voltage and current that you would use them at (combined with the short ON time of this app), you might be able to get away without any heatsinking. You would just need to solder on a few connecting wires.

Yes, I actually have one, I can not hardly see the post on this thing. The Iron I have would flood the entire chip with solder. These chips would be a dream come true if you can handle the soldering.

 

[jimR]

Hey Hoog
This may work: http://www.onsemi.com/pub_link/Collateral/NTP18N06L-D.PDF

Not sure but the graph looks like you could get the current you would need at 2.5 to 4 volts.

 

[hoogie76]

Thanks jimR.. I'm gonna check this one out.

Fairchild actually makes an ldo regulator with a control pin but it's for 3.3 volts.. If it were just a bit higher...

 

[h8isgr8]

Yes, I actually have one, I can not hardly see the post on this thing. The Iron I have would flood the entire chip with solder. These chips would be a dream come true if you can handle the soldering.

Awe, c'mon...... they're not that small.

I routinely solder SSOP IC's with nothing more than a $10 wal-mart iron, so stuff like this isn't really a challenge for me anymore (yes, I'm bragging).

Here's an example of what a $10 iron and a steady hand can do......

\


I have some of these small FETs from TI (forgot which ones exactly). I'll try wiring one up later and let you know how if goes.

 

[hoogie76]

Ahh.. Nice job but my old eyeballs and shaky hands would produce one line of solder across all the pins not to mention the burnt off runs

Although I did buy some flux pens for attempting to do some smds.

 

[jimR]

I think I could solder the nickel..lol

 

[hoogie76]

haha.. you guys crack me up..

 

[h8isgr8]

I found some time to throw together a circuit with one of these TI FETs. Works like a charm. The FET doesn't even get the slightest bit warm during use.

I say get some good solder (0.015" silver bearing stuff from rat-shack) and give it a try. You just need to be confident in what your doing. If I can do it, anyone can; I don't have any special professional skills. I'm a janitor for god's sake.

 

[jimR]

I ordered some TI Samples this morning. and will pick up the better solder at the ratshack. Thanks for the photo.

I do not see a resistor on the gate? Can you use without one?

 

[h8isgr8]

I do not see a resistor on the gate? Can you use without one?

It's there, under the red wire, soldered directly on the FET (squint really hard).

 

[jimR]

Recieved the TI Mosfets Friday and built the 1xAA box mod today. Works like a champ. Vaping about 4 hours and still producing great vapor. No switch drop out. Soldering did require a little patients but not to bad.

Jim

 

[h8isgr8]

Recieved the TI Mosfets Friday and built the 1xAA box mod today. Works like a champ. Vaping about 4 hours and still producing great vapor. No switch drop out. Soldering did require a little patients but not to bad.

Jim

Congrats Jim!!! I told you there was nothing to be afraid of.

 

[Guineahill]

I was thinking a small resistor could keep the gate voltage under 4.0 in the event of a full battery but still stay within range for a low battery. It'd only need a .2 volt drop to stay in range and the gate off is less than a protected li-ion batt cutoff. I like the package style so I've been staring at it for a while..

Unfortunately, last time I took electronics, nand gates were the big new item.

Hoog

Oh gee... when I was in school nand was the thing also. Hadn't thought about that in ages!

 

[petercro]

Jim, how good are your soldering skills?

TI has a line of MOSFETs with perfect specs for low voltage/high-current apps.......

Power Management - MOSFET - CSD16325Q5C - TI.com

For the voltage and current that you would use them at (combined with the short ON time of this app), you might be able to get away without any heatsinking. You would just need to solder on a few connecting wires.

Hi I'm trying to source these in the UK,
can anyone point me in the right direction.
Also do thay work as a touch switch.
I've tried using a irf510, It will quite happily light an LED. 3.7v drain and gate voltage.
3.7v across the LED on meter.
But the moment I put an atty in as the load, the voltage across the atty drops to .5 to .7v ish
I do realise that the atty is drawing power away from the gate, but am I doing anything else wrong.

Thanks in advance
Peter..............

 

[Scottbee]

I quickly looked at the specs on the irf510, and at first blush it looks like the threshold voltage is going to be too high for this application.... a FET with logic level switching would be preferred.

That being said... how do you have it wired?

P.S. Can you get Digikey stuff over there?