EverCool Variable Voltage Mod

[Old_Trekee]

CraigHB, Thanks very much for the quick and very informative reply. I'm planning on making a couple minor changes. I am going to use a 4 AA box and I'd like to put a madvapes Voltage Display in the circuit. Would adding the ceramic capacitor on the input smooth out the ripple effect? I read in an earlier post that some people had problems with the Voltage Monitor due to the ripple effect. Also, if it will help, how many uf ceramic cap should I get.

Thanks again for all your help.

 

[CraigHB]

Welcome,

Yes, I've seen reports of sensitivity on the madvapes voltage meters. I would go ahead and try the meter using only a couple good quality electrolytics. If the meter has issues, then you can try adding ceramic caps as indicated by the data sheet.

One thing a little different I do myself is to run a couple higher value MLC ceramics in parallel. That actually works a little better at smoothing things out than an electrolytic and ceramic. I believe that data sheet was written before those became affordable (only recently). They used to be cost prohibitive. With a couple 47uF MLCCs in parallel, you can get capacitance high enough to cover the low frequency stuff while increasing the effectiveness at smoothing high frequency stuff. For surface mount, it's a lot better because of the much smaller profile, however they're still relatively expensive. If size is not an issue, then an electrolytic and ceramic would be the least expensive route.

 

[Old_Trekee]

CraigHB, Thanks again for the info. Would a 100uf MLCC do just as well as 2 47uf's or should I get the 47uf's. I'm going to go ahead and order them just in case I need them. Thinking that 1 100uf would take up less space if it'll work just as good.

 

[breaktru]

Welcome,

Yes, I've seen reports of sensitivity on the madvapes voltage meters.

Hey Craig, I don't recall seeing any other complaints about the 1s-6s meter (same as madvapes) than the postings I made about it.
I experienced a problem using it with a digital pot when it bottoms out at the low end of the voltage scale near 3.1v, probably insufficient voltage to power the display (Meter Dims), pwr the reg, pwr the D.P and provide D.P. scaling. Plus the meter pulsing to check alternate cells (1-6) probably doesn't help.
Other than that it works fine above 3.5v.

 

[CraigHB]

Thanks for clarifying that. My memory was never that great and it's not getting any better. I often see things then forget details so if you are the only one, you are the only one. That's good though. I would expect that meter can handle a little ripple.

@ Old_Trekee, a 100uF MLCC should do the job, just as well as an electrolytic. There is an advantage in using two capacitors in parallel (reduced ESR), but we're not particularly concerned about that. We don't have to heavily filter the input and output on these things because we're only powering an atomizer. There are plenty of situations where you would need a super clean output, but this aint one of 'em.

 

[Jesper]

Several people have asked about using a pot (potentiometer) with a different value than that defined by BigBlue whether it's cause they can't find the right pot or other aesthetic reasons. It is possible. You can use a higher valued pot with a fixed value resistor attached in parallel to the pot.

Here is how it will attach to your (non spec) pot. You could call it an equivalent pot circuit.

View attachment 42880

Here is a link to a calculator to determine the value of R2 (fixed resistor) based on the value of R1 (Pot) that you want to use. Any parallel resistance calculator you can google will probably work equally well if the above link becomes dead for some reason. In the above example it's assuming you want to use a 1k ohm pot. That would require a 250 ohm fixed resistor in parallel to give a total resistance ranging from 0 to 200 ohms in the equivalent pot circuit.

R1 is your Pot, R2 is the fixed value resistor you're adding in parallel and Rtotal is circuit equivalence. Just replace this circuit of (Pot and fixed resistor) for the (Pot) in BigBlues original schematic. Everything else remains unchanged.

The 220 ohm resistor you're referring too remains unchanged for this purpose. It's there to limit the maximum output voltage. It's in series with the (pot) and should remain in series with this (equivalent pot circuit). Technically.... according to the spec sheet from Texas Instruments, that 220 ohm resistor should be 241 ohms but that's picking at nits. A 220 ohm resistor is fine and works great (and is easier to come by than 241 ohms). It just means that your max output voltage will be a little higher than 5.5v per the spec sheet. It should be soldered to the same leg of the pot as in the original schematic. In the example schematic above the 220 ohm resistor would attach to the left leg and ground (pin 3 of the Ti chip) would attach to the right leg.

The wattage of the pot and fixed resistors can be 1/8 watt but if you can only find 1/4 or 1/2 watt parts they will work just as well but will take up more room due to form factor.

Whenever possible it's best to stick with BigBlues original design and schematic for the sake of the K*I*S*S method (keep it simple stupid) as this change only serves to complicate things. I would only use this parallel resistance technique if you're either desperate or determined to do so.

Thanks a lot for your detailed explanation

So I hope I got this right, if I use the below diagram, on which points should I solder the new resistor, in case I replace the old potmeter?

To leg 3 on the TI and to ???

 

[Old_Trekee]

Jesper, If you were to use a 1k variable resistor in place of the 200 ohm resister, the 250 ohm fixed resistor would go from the center pin of the variable resistor to the left hand pin in the same row as the right hand side of the other fixed resistor. You could put the 2 fixed resistor in series if that makes sense. I'm going to try the same thing and see how it works so I can use a thumb wheel variable resistor and have it come thru the case for external adjustment.

Thanks again for the excellent info CraigHB.

 

[CraigHB]

Welcome, hope things work well for you.

 

[rchriste]

Thanks a lot for your detailed explanation

So I hope I got this right, if I use the below diagram, on which points should I solder the new resistor, in case I replace the old potmeter?

To leg 3 on the TI and to ???

The new fixed value resistor would connect to F-3 and F-4 Jesper.

 

[Jesper]

Thanks a lot for your help rchriste and Old_Trekee

I got it now

 

[Jesper]

One more question!

I have now put it all together and it works fine (almost) with the new pot and resistor.
But it's like the pot only uses less than ½ a turn to go from 0 - 6 volt and not the full turn.

Have I maybe soldered the new resistor to the wrong legs or aybe something else or is it supposed to work like this?

 

[rchriste]

One more question!

I have now put it all together and it works fine (almost) with the new pot and resistor.
But it's like the pot only uses less than ½ a turn to go from 0 - 6 volt and not the full turn.

Have I maybe soldered the new resistor to the wrong legs or aybe something else or is it supposed to work like this?

You're using components that are not the values you think they are if I'm reading you right. I'd remove the Pot and Fixed resistor and measure them separately and in parallel. I'm looking at the spec sheet and it says that Rset has to be higher than 131k in order to get to 0v. You should be bottoming out around 3.2v or 3.4v but nowhere near 0v. Your pot (w/fixed resistor in parallel) should be reading around 0 to 200 ohms and not 0 to 200K. Also check the value of the resistor that's in series with the pot. Make sure it's 220 ohm. Sounds like it's adjusting .... just not the way you would want it too. I'm using a 500 ohm pot with a 220 ohm fixed in parallel (0-152 ohms) and a 220 ohm in series and I get a range from 5.5v to 3.8v That was my personal preference.

I would have to guess your problem is a component that's not measured in ohms but in kohms.

 

[bstedh]

double check the values of the components you have and they should be wired in like this.

You want the ohms of the two red components to have a total ohm reading of 200 when the pot it turned all the way up and 0 all the way down. The 220 resistor needs to stay to limit your lowest resistance or highest voltage.

Resistance calc
Use this to calculate the values you need. Put the rating of the POT in and the total of 200 ohm and calculate for the resistor you need in parallel. Also pay attention to the drop down labels on the calculator.
So for a 47K ohm pot you need a 200 ohm resistor in parallel. A 47K and 200K give you 38K.

You can also remotely locate the POT by extending F3 and F4 with wire to the center and one outside leg of the POT. Which outside leg you use will determine if the value goes up or down with a specific direction of turn. If the POT acts the opposite of what you want just use the other outside leg instead. Or if its board mounted and seems to work backwards just flip it around. F2 is a dead connection and has no importance.

Here is a pic of one I did with all 3 resistors remotely located.

This is a 500 ohm POT and 500 ohm resistor in parallel and 200 ohm in series.
The Green wire with this would go to either E3 or F3 and the blue wire would go to E5.

If you where to measure the ohms between F3 and E5 you should get between 220 ohm and 420 ohm when you adjust the POT from one end to the other.

 

[ledouxmike]

Great thread. Was just wondering what I would need to do to bring the output voltage to 6 volts and what the disadvantages are. Also, what size box will I need to add a madvapes meter and a couple big switches, one for the trigger and one for power. I was thinking about getting a main power switch that lights up. thanks

 

[rchriste]

Great thread. Was just wondering what I would need to do to bring the output voltage to 6 volts and what the disadvantages are. Also, what size box will I need to add a madvapes meter and a couple big switches, one for the trigger and one for power. I was thinking about getting a main power switch that lights up. thanks

When I added the MV meter and a 500 ohm single turn panel mount pot, I used this box from Mouser. It doesn't include the battery contacts. You have to order them separately. It has a battery compartment separate from the components compartment. The battery door slides off like you would see on a remote control device. It's a little fat but I think everything you want to use might just fit in there. Your switches will need to be low profile though. That switch you used to start the 1947 ford pickup won't work in this box. The dimensions are in the data sheet on Mouser. You can check it against your switch. The MV meter does in fact fit in front of the battery compartment. The small footprint panel mount pot I used fit nicely between the battery compartment and the exterior side. The advantage to this box for me was not having to remove screws or pry a box apart to change the batteries.

I don't know of any advantage or disadvantage of 6V on this mod. Maybe someone else can answer that for you.

 

[rchriste]

But it's like the pot only uses less than ½ a turn to go from 0 - 6 volt and not the full turn.

I have one more comment about resistor terminology here in case you're missing it Jesper. If I'm overstating the obvious to you then accept my apology.

2 ohms = 2 ohms
200 ohms = 200 ohms
2k ohms = 2,000 ohms
200k ohms = 200,000 ohms
2m ohms = 2,000,000 ohms
200m ohms = 200,000,000 ohms

For the fixed resistor values... this is a good color code reference calculator. Click on red for band one, red for band two and brown for band three and this calculator will give you 220 ohms which is correct. I haven't tried it beyond that. Hopefully it's 100 percent correct. I just google'd it.

oh and one more point.... before I told you to put that new resistor between F-3 and F-4 (which is correct) but bstedh's picture with it between E-3 and E-4 will also work. Neither method is more correct that the other as they are both correct. I also agree with bstedh on using the remote pot method. All three methods put a fixed resistor in series and a fixed resistor in parallel to the pot and all three methods are correct. I used that remote wire method with mine to put the panel mount pot over on the side of my box and away from the pcb that is used in this mod.

 

[ledouxmike]

I found my box in 2 sizes. 3.9 x 2 x .8 and 4.4 x2.4 x 1.1 I wanna go with the smallest box I can. This is the one I've got my eye on.

 

[rchriste]

I found my box in 2 sizes. 3.9x2x.8 and 4.4x2.4.1.1 I wanna go with the smallest box I can.

I would agree.... go with the smallest one you can unless you have a particular reason not too. My box measures 3.0x2.1x1.2 but I had a particular reason to use that specific box. I had all kinds of room left over for a meter so I added one. It sounds like yours are a bit on the long side (.9" to 1.4") longer than the one I picked and a bit shallower (.4" - .1") but there's no way for us to know how you want to orient your parts. Just off the top of my head, it seems like you've got room for even more than a meter with either of those two boxes. Maybe you *DO* have room for that 47 Ford Starter switch after all. <giggle> How can you go wrong with a 30 Amp switch that you have to push with all your weight using your foot. <snicker>

I guess I don't understand your question. If you already have the box you want to use and know it's dimensions, already have the switches you want to use and know their dimensions, already have the meter you want to use and know it's dimensions then what is it exactly that you need to know about the size of the box? It seems like the answer would be 'choose one of them at your own discretion'.

If you don't have the meter yet and need to know what it's dimensions are then that would be a different question. I'll go check that... hang on...

Mine from MV measures 0.925"-Width x 0.750"-Height x 0.400"-Depth. That's *pretty close* to the dimensions that MV states on their website for the meter.

If that's not what you're asking then please restate your question in a different way.

 

[ledouxmike]

The only part I have is the TI chip. I haven't ordered any other parts yet. I'm just doing research before I order all the parts. I just wanted to make sure everything would fit in either box, that's all. I went to radio shack and saw a small 4x2x1 box they had. It looked really small to me. I can't believe you fit everything and the meter in the box you used. Sounds like either box will work then. thanks

 

[rchriste]

The only part I have is the TI chip. I haven't ordered any other parts yet. I'm just doing research before I order all the parts. I just wanted to make sure everything would fit in either box, that's all. I went to radio shack and saw a small 4x2x1 box they had. It looked really small to me. I can't believe you fit everything and the meter in the box you used. Sounds like either box will work then. thanks

You're quite welcome ledouxmike.

Believe it or not... there's actually quite a bit of room in mine after adding the meter. I could easily add a mini USB charger port, a 2 cell charger pcb and a touch switch pcb and *STILL* have some extra room for an MP3 player chipset. Of course I won't be doing that to mine for obvious reasons but if my wife requests it.... it's all do-able.

If you're only adding a meter then (just a suggestion) you might want to make sure you've looked at all of your options before you order the box. You could do with a box smaller than yours and smaller than mine assuming you use the lowest profile switches you can find. If you want the smallest size possible then I'd order all of the components *EXCEPT* for the box, lay them out in front of you and then you'll have a 'for sure' idea of what size box you'll need. If you want to save on shipping by ordering the box at the same time you order the other components then you're going to have to do all your research before you order. It's a little harder to do that way but fortunately, you have access to all of the dimensions of the parts you'll be using.

If you need any measurements of components, just yell and I'll be glad to measure stuff for you.

To answer your question though... you'll have plenty of room for a meter in either of those boxes assuming small footprint switches. Without knowing the dimensions of your switches I'm afraid it's going to have to be your call but even with switches larger than the smallest ones you can find... I still think you'll have room especially since your boxes are so long.