My first Variable Voltage Boxmod

[asnider123]

I know, a bunch of you guys already have made numerous variable voltage mods, but this is gonna be my first. Thought I would share this with you as it progresses.

Well, I got this schematic online and thought I would try it, since I have all parts I need. I borrowed the schematic from a fella in The Phillipines. The original designer called it the "Poorvari" (you get it?) .. it takes an LM350T VVR, 3 resistors, 1 trim pot, a switch, an LED and an atty connector.

Step 1: Study the schematic



Step 2: Breadboard the circuit



Since I did not have the exact resistor values, I substituted 220 ohm for resistor #1, and 470 ohm for resistors 2 and 3. Well, it works and it works great. In preliminary testing, it adjusted above 6V+ at the high end and I went as low as 2 volts before I quit testing. The 1K trim pot I am using is a 'screw type' and is adjustable very precisely, as you turn the adjustment screw many time end-to-end.

Anyway, it looks like the circuit is gonna work great, so the next step is to install components into the 3-aa box.

Hope you have a nice Memorial Day

 

[Dalton63841]

Congratulations! You will enjoy it I'm sure. I did the same thing with my resistors. I used a 220, a 330, and a 470.

 

[Hogwart]

I'm gonna have to get me one of those breadboards and learn how to use them, would have saved me a whole lot of headache on a couple evercool mods I still cant get working.
Look forward to seeing the finished product.

 

[mwa102464]

Looks great, I loved everything until you got to the AAA batt box, I was hoping for dual 25500 Batts in the smallest box you could fit them in side by side, anyways nice job though, if ya ever find a unique enclosure for 2 x 25500 let me know please.

 

[donptal]

Your schematic looks familiar lol. I'm reading your post as I vape my poorvari and I'm hoping that you will finish modding yours and appreciate its performance considering its dirt cheap cost. Goodluck asnider!

P.S. Don't forget to heat sink your regulator.

 

[TomCatt]

This will be your first VV, Alan? I'm amazed. I figured you would have 3 or 4 done by now . Post some pics when your done

 

[asnider123]

Your schematic looks familiar lol. I'm reading your post as I vape my poorvari and I'm hoping that you will finish modding yours and appreciate its performance considering its dirt cheap cost. Goodluck asnider!

P.S. Don't forget to heat sink your regulator.

Yah, I read that .. how did you heatsink your 350? It worked fine on the breadboard, but in a plastic box it may be a problem.

Thanks for your most excellent simple VV design, you are a genius

 

[Dalton63841]

Yah, I read that .. how did you heatsink your 350? It worked fine on the breadboard, but in a plastic box it may be a problem.

Thanks for your most excellent simple VV design, you are a genius

Mine is not heatsinked, but I kinda get the idea you are a much heavier vaper than I am...

 

[asnider123]

Mine is not heatsinked, but I kinda get the idea you are a much heavier vaper than I am...

That's kinda what I was thinking .. I am not a chain vaper but I DO want it to work efficiently. I tried a heatsink, but it blows in my face .. besides, it's hard to fit in my pocket .. perhaps I need to reverse the fan



Seriously, I can see what Donptal is saying, in a closed plastic box I may have heat problems if I vape very heavily. Wonder if a larger tab or a coin would be an adequate heatsink or if I need to ventilate the box ??

 

[Dalton63841]

That's kinda what I was thinking .. I am not a chain vaper but I DO want it to work efficiently. I tried a heatsink, but it blows in my face .. besides, it's hard to fit in my pocket .. perhaps I need to reverse the fan



Seriously, I can see what Donptal is saying, in a closed plastic box I may have heat problems if I vape very heavily. Wonder if a larger tab or a coin would be an adequate heatsink or if I need to ventilate the box ??

Haha Wow that is an epic heatsink! A drop of arctic silver and a small square of aluminum about the same size as the regulator would probably be sufficient. I have heard of people taking the small heatsinks from like a motherboards northbridge and grinding them down small enough to fit and using them.

 

[donptal]

THiS to220 heatsink is the one that i'm using and its working perfectly without the need for a fan.

 

[breaktru]

Congrats Alan on your first VV. The fan cooler is a nice touch even if you were joking. Who knows you may have started a new trend. External cooling.

 

[asnider123]

Well, I got it working. I had fried my voltage regulator by over-heating while soldering (my fault)!!! Tore it apart and rebuilt it. Anyway, it's up and running really good!!

Specs: 2 x 14500 batts
6 amp button
LM350T variable voltage reg (3 amp)
801 recessed carto
Trimmer potentiometer
Internal LED

Range: about 2V up to 6v+. I find my favorite voltage is around 4.7v (yes, I agree with you guys, that's the "sweet spot" alright!!

Cost to build:

LM350T regulator $1 (Ebay)
3-AAA box $1.25 (Ebay)
Button convex $1 (goodprophet.com)
801 connector $1 (goodprophet.com)
Trim Pot $0.25 (Ebay)
Resistors,LED $0.00 (had already)

Total cost: $4.50

Pretty good, eh?

Pics:

Inside wiring (it's kinda messy but oh well, it works)


Closeup of voltage adjustment screw


Honk, honk (LOL)


Vape, vape

 

[Noodoggy]

would you be willing to do a step by step tutorial? also i was wondering how you solved the heat sink problem? Great value for a VV mod! Awesome job! you might have started me on my path to a modder future lol

 

[asnider123]

would you be willing to do a step by step tutorial? also i was wondering how you solved the heat sink problem? Great value for a VV mod! Awesome job! you might have started me on my path to a modder future lol

Tutorial .. yes, this was my prototype, didn't know how it would work out. Will photo step be step next time

Heat sink .. I am not a chain vaper, I just let the LM350T float so air could travel clear around it. Time will tell whether this was a good idea. If I have heating probs, I have more ICs and will attach a heatsink. I just wanted it as compact as possible, so I am riding bareback I do feel a bit of warmth where the chip is located, when it feels a little warm, it's time to take a break

 

[Noodoggy]

Thanks for the reply! i unfortunately chain vape at times lol so i guess those heat sinks are big!? i have no idea lol IC = integrated circuit? forgive me; i am total noob lol I have subscribed to the thread so i will eagerly await your step by step photo tutorial! And as for me, I am not looking so much for compactness, but i am definitely looking for form factor. I used to smoke a pipe, and would love to replicate that tactile sensation but not necessarily in the same form factor as a pipe. i have a feeling i will have to get out some modeling clay and create a form and see if someone can make a 5v mod out of it lol

 

[donptal]

Well, I got it working. I had fried my voltage regulator by over-heating while soldering (my fault)!!! Tore it apart and rebuilt it. Anyway, it's up and running really good!!

Specs: 2 x 14500 batts
6 amp button
LM350T variable voltage reg (3 amp)
801 recessed carto
Trimmer potentiometer
Internal LED

Range: about 2V up to 6v+. I find my favorite voltage is around 4.7v (yes, I agree with you guys, that's the "sweet spot" alright!!

Cost to build:

LM350T regulator $1 (Ebay)
3-AAA box $1.25 (Ebay)
Button convex $1 (goodprophet.com)
801 connector $1 (goodprophet.com)
Trim Pot $0.25 (Ebay)
Resistors,LED $0.00 (had already)

Total cost: $4.50

Pretty good, eh?

Pics:

Inside wiring (it's kinda messy but oh well, it works)


Closeup of voltage adjustment screw


Honk, honk (LOL)


Vape, vape

Congratz asnider! My question now is, are you satisfied with its performance considering that it is very cheaply made ($4.50 heh) to function? How long your trustfire last? Please update us regarding its performance. Congratz again asnider!

 

[asnider123]

Congratz asnider! My question now is, are you satisfied with its performance considering that it is very cheaply made ($4.50 heh) to function? How long your trustfire last? Please update us regarding its performance. Congratz again asnider!

Thank you Donptal, it is your divine design after all (Poorvari). I must tell you that this is my first experience with a VV and I must say I really love it! And YES, it was unbelievably cheap to make. I am lucky to be in the USA, where there are so many inexpensive parts distributors. Also, I have patience and it does not bother me to wait 3-4 weeks for parts from Hongkong to be shipped. If price is less than $15, I do not have a worry having to pay customs or anything. Very lucky.

Battery life .. I don't know yet. I built it last evening and populated it with NOT fully charged batts (they read 3.8v each) .. it is still working great. I have perhaps 3-4 hours on these not-fresh batts so far.

My vaping style is: press button 1/2 second to heat, then two mouth draws to fill mouth .. let go of button .. then inhale. Timing it, I fire the unit for approx 4 seconds at a time, then let it sit a while before vaping again. I suspect my batteries will last a long while between charges.

Questions if I might ...

I know I made a cardinal error .. I know you said heatsink but I was in a hurry to put together the unit. My LM350T does heat up a little, but not yet enough to melt plastic or anything. Since I bought several of the chips, I can always rebuild if I need to. So far it has worked well. Does the LM350T blow if overheated or does it have thermal overload protection? I think I did that when soldering my first one, I was much more careful with the second (I used alligator clips as heatsinks while soldering)

I used only 1/4 watt resistors. Since the are feeding the ADJ pin, that should be adequate, eh?

I used a screw-type trim potentiometer for the circuit, that way I can be accurate in my adjustments. I did notice that there is a difference in loaded and unloaded voltage. Interestingly, loaded voltage is actually higher than unloaded ??? I set it for 5v with no atty, then tested with 3 ohm atty and it was more like 5.3v. I thought it would be the other way(?) Is this normal?

What voltage do you find the best for you? Anything higher than 5v seems to have a harsh taste with these 801 cartos, I like it best around 4.7-4.8v

I ordered 10 more 3-AA boxes, if this works well (and I am sure it will), I am going to make more for family members and friends.

Thank you again for your most excellent simple design. You are a genius.

Alan

 

[asnider123]

Update .. I have ordered TO-220 heatsinks for future builds off Ebay .. 10 for $2 .. from Hongkong. From dimensions, they should fit perfectly in AA box ..

 

[asnider123]

Hey Donptal, is the lm350t tab in common with one of the pins or is it floating?