Just For LM2596 Users

[Quigsworth]

Standby current is only ~80uA so battery drain concerns are minimal at best.

Thanks Rader...I was looking high and low trying to find that...I seem to remember reading somewhere you could hook up one of these regs to a batt for a week straight then pick it up and vape on it...

 

[BJ43]

Here's my reasoning for switching the output, feel free to debate it, I love a good "constructive" discussion


By switching the input on these regs you are "constantly" subjecting the little guy to inrush current causing thermal stress every time you hit that fire button...you are shortening it's lifespan significantly...ok, sure, they cost $2 so meh but you still have to put your mod up on the hoist, pull the reg out, break/make connections, bla, bla, bla...just to save "maybe" a cumulative 5-10 mins. a week in batt life???...I just want to vape...

I'm going to go as far as to "suggest" you switch the output, switching the input to gain runtime just doesn't pass the cost/benefit analysis test IMO...our batts are rechargeable remember?

Have to go back at least 50yrs to get so much pleasure from a $2 investment.

 

[slimest]

Quigsworth, easy to test your suggestion: just connect a LM2596 board to batteries and measure input current. I don't think that it will be close to zero. If so, also imagine that something got wrong with the board (bad capacitor etc). In this case if you haven't an input switch, current consumption may be out of your control, so explosions, bloody fingers etc. I don't think that your recommendation is suitable for electronics novices.

 

[Quigsworth]

Quigsworth, easy to test your suggestion: just connect a LM2596 board to batteries and measure input current. I don't think that it will be close to zero. If so, also imagine that something got wrong with the board (bad capacitor etc). In this case if you haven't an input switch, current consumption may be out of your control, so explosions, bloody fingers etc. I don't think that your recommendation is suitable for electronics novices.

I like it, constructive, provocative...makes me go hmmm...(I love this forum )...and Slimest, your point of not recommending this switching method to novices is well taken...

...I read your response last night and decided to think about it some more...one thing I didn't do was qualify my suggestion by taking into consideration the deployment of this reg (a pretty big oversight on my part)...is it a PT, paired with a PSU?...is it hard-wired into your car like I have done?...is it in a hand held device?...is that hand held device also a PT?...does it have a meter?...and to throw a "real" big curve into this discussion, is it being tact switched? (but let's leave that one alone, it's a game changer)...the list of uses goes on and on with these regs...

For the sake of keeping this meaningful, let's go with Foxman's use. It's a great example of taking the basic batt/switch/atty box to the next level.

1st off, I am by no means recommending that there "not" be a master on/off switch between the batts and reg, that should be a given but it should be noted, when you're done vaping and you put the device in your pocket/bag/whatever, turn it off (or pull the batts)....that being said,

There are inherent risks to these devices we make and having a constant potential on the input and the issues that could arise from that has crossed my mind on a number of occasions...I'm forever forgetting to turn off my shop laptop PSU PT (I've now put an LED behind the master on/off )...but after weighing the risk pro's and con's I still came to the conclusion that I would rather be holding a reg that is warm with a stand-by current flowing through it when I press the fire button than one that is cold and with a button press, instantly connect 7.4v and a capacity to run 10A+ through it...in my experience, that's when components "pop".

...is there any empirical evidence that suggests that one method is safer than the other? I guess 2 regs could be bench tested to destruction with a timer and a relay, might be worth it "just to see"

As a final note, I don't really take issue with seeing either switching method, both have their pros/cons but if I ever post a handheld device with an LM2596 switched at the output (and it will be) and someone chimes in with "you've done it wrong", be prepared to back-up your statement with a clear, cogent explanation as to "why" you think I've done it wrong

 

[Illuminatu]

Finally got around building the VV with the LM2596, sadly i broke my block of wenge, so its assembled in a cheap plastic project box. I won't post pictures yet since its ugly as hell, but i can say this outvapes a lavatube by far !!! pictures to come when transfered in wood

 

[TommyO]

I'm looking to pull the potentiometer to remote mount it, but I want to use a different one that has fewer turns and has a better knob. Any suggestions? Thanks

 

[Illuminatu]

Yeah that would be a great idea (chaging potientometer), and I'm running into a few weird issues with the lm2596, it wont go lower than 4.7volts without shutting down the whole unit, and it seems to not take the any higher than 7.4 volts even tho i use 2 freshly charged 18650 that get off the charger at 4.2 volts .... I'm stumped, maybe one of my switches or something is eating up the voltage and creating resistance ?

 

[Rader2146]

These things do have some voltage dropout, so 7.4v on fresh batteries is within the norm.

You can change the trimmer. Somewhere in here is a couple posts about changing it out, but im on my phone so it's difficult to find right now.

 

[Rader2146]

Found it. Start here and read a couple pages.

http://www.e-cigarette-forum.com/forum/battery-mods/259577-just-lm2596-users-36.html#post5941451

 

[Illuminatu]

Thanks Rader2146, I'll take a look at it, coz this chipset is quite cool but my 1.5 ohms genesis coil doesnt like running at 4.7volts under load lol it burns all liquids

 

[TommyO]

Thanks I'll do some reading.

 

[Rader2146]

To change the minimum voltage you will need to change R1. I have been trying to figure out how to calculate R1 based on desired minimum voltage but that seems to be beyond my knowledge.

Maybe Java could share how he calculated for the minimum voltage if he's listening.

 

[TommyO]

To change the minimum voltage you will need to change R1. I have been trying to figure out how to calculate R1 based on desired minimum voltage but that seems to be beyond my knowledge.

Maybe Java could share how he calculated for the minimum voltage if he's listening.

lol I was hoping I could just desolder the blue one that is on the board and replace it remotely via some wires to another place in the mod, having one that has fewer turns would be great but not a requirement, and a better knob setup.

 

[TomCatt]

I believe just swapping the 10k ohm pot with a 5k ohm will give a better adjustment for the 'vaping range', according to previous discussions about this.


Picked this up today - Unique Wooden Box handmade Brown Decorative With Latch | eBay

Gonna make a desk top PT using either the larger LM2596 - LM2596 DC-DC Converter 4-40V to 1.5-35V Step-down Adjustable Power Supply Module | eBay
or this kis 3r33 plug-n-play module. I have both modules around here somewhere , just can't find either at the moment. I ordered another kis-3r33 module today also. Also have a slightly smaller box on the way that I may put together with one of the smaller LM2596s.

Ooops, fergot to give the devil his due credit for the idea - http://www.e-cigarette-forum.com/forum/modding-forum/192284-dear-gummy-17.html#post6508163

 

[Quigsworth]

That's a cool box TC, that'd make a great PT...you may want to consider installing a tiny 1" PC case fan in that bad boy though...it looks like the box is up on feet...2 holes in the bottom with a 1" spade bit, mesh over what will be your air "in" to keep the bunnies out...run the fan off your V out...just a thought.

 

[TomCatt]

I don't do high wattage vaping, Q. I have yet to feel any warmth from my LM2596s - I've even held my finger on the chip while chain vaping, nada. But a good idea, and something to keep in mind.

 

[Rader2146]

I've only notice mine put off a considerable amount of heat one time: when I forgot to turn the power down after switching from a 3 ohm to a 1.5 ohm carto. 5.2 volts, 18 watts and 3.46 amps. I wondered why my vape had no taste until I checked the voltage. After that, I have no doubt of the durability of these chips.

 

[Rader2146]

lol I was hoping I could just desolder the blue one that is on the board and replace it remotely via some wires to another place in the mod, having one that has fewer turns would be great but not a requirement, and a better knob setup.

If you low voltage is OK then you can do exactly as you described. Use the trimmer and knob of your choice and wire it in. The R1 value plays a huge role in the max voltage so you'll have to verify the calculations for the R1 value of your board. I have a blue board and 2 green boards and they have a different R1 vallue: green boards=331ohms, blue board=471ohms. Choose the correct value trimmer and a single turn with a knob should give you all the resolution that you need.

Here is a table of the max volatges based on different trimmer values. Notice the relatively broad difference on output when the only thing different is the R1 Value:

R1	331
	
R2	Max Out
500	0.63
1000	2.49
1500	4.34
2000	6.20
2500	8.06
3000	9.92
3500	11.78
4000	13.63
4500	15.49
5000	17.35
5500	19.21
6000	21.07
6500	22.92
7000	24.78
7500	26.64
8000	28.50
8500	30.36
9000	32.21
9500	34.07
10000   35.93

R1	471
	
R2	Max Out
500	0.08
1000	1.38
1500	2.69
2000	3.99
2500	5.30
3000	6.60
3500	7.91
4000	9.22
4500	10.52
5000	11.83
5500	13.13
6000	14.44
6500	15.74
7000	17.05
7500	18.36
8000	19.66
8500	20.97
9000	22.27
9500	23.58
10000   24.88

With R1=331ohms a 2k trimmer will give you a realistic high value of 6.2v, but with R1=471ohms and the same 2k trimmer you'll only get 3.99v.

 

[hificat101]

Awesome chart Rader. Where were you when I ordered 5K Piher pots for mine? At the time that seemed to be the consensus. Anyway, as far as pots go, Mamu actually tipped me off to some awesome Piher pots that are available from Mouser cheap. She said she has used a ton and never had a failure. They have a rotational life that is way beyond the stuff typically available to us, and their cheap. You can get them in either top adjust, or side adjust configs, but I think the coolest thing about them is they have a hole in the center, and you can buy shafts or thumbwheels for them. The shafts are a nice size, and have an arrow on the end so no knob is required. They cost about 49 cents a piece, and the shafts are about 19 cents. Great deal.

Anyway, here are the 5K ones I bought (side adjust):

PT10MH01-502A2020-PM Piher | Mouser

Here is the shaft:

JPEPL5012NE Piher | Mouser

And here are the white thumbwheels I bought for them, but haven't had a chance to stick in yet to see if they fit, but they look like they will:

XBOPL5034INI Piher | Mouser

Unfortunately, they aren't available in 2K or 3K. I'm thinking if I can find the proper resistor value to throw on the wiper, I'll be fine. I'm probably going to have to cipher it out twice though, as I have both the green and blue boards.

 

[Quigsworth]

I don't do high wattage vaping, Q. I have yet to feel any warmth from my LM2596s - I've even held my finger on the chip while chain vaping, nada. But a good idea, and something to keep in mind.

No doubt, but don't ya just love putting fans and ..... in things? ...I'd also drill a couple 5mm holes through the bottom and install a couple orange or red leds for some ground effects lighting...nothing gets chicks like ground effects lighting...or so my kid says