Tinkering with the OKL2-T20 20A 110W dc/dc converter...

[CraigHB]

I am curious on what other dc to dc converters are out there that could be used in our hobby.

Any converter with the right input and output range.  These POL modules as they're formally called are widely produced and generally used a lot in electronics.  The buck modules (step-down) are by far the most common compared to boost or buck-boost.  The higher output parts we need for an e-cig are less common, but they seem to have picked up in offerings over the last few years.

New models trickle out slowly but surely so you have to sort of keep your eyes peeled on what makers are offering.   Texas Instruments is a big maker and so is Murata.  GE has some good offerings as well.  There's many more brands than that, but those guys probably have the widest product range.

[ModManCooper]

Thank you for the response!! I posted on the main page about the 40a raptor. Any advice would be extremely appreciated!!!

[BFBCAcid]

I was wondering does the OKL2-T20 20A 110W converter step down? I tried to read the datasheet but must be missing it or it can't do it? If so how can I tell?

[Visus]

I was wondering does the OKL2-T20 20A 110W converter step down? I tried to read the datasheet but must be missing it or it can't do it? If so how can I tell?

Read features on the specs sheet it tells you there..

it can step down from 5.5v to all the way in the gutter @ 0.69,  it cannot step up. 

A booster/step up regulator has a hard time stepping down the okl is a buck converter it steps down from a set voltage from input usually thats at least 1v lower than input.  8.4v input, becomes dialable from 0.69-5.5v output.


Programmable output voltage from 0.69-5.5Vdc



It cannot step up

[BFBCAcid]

Thank you for the response VISUS but I'm still lost.

Maybe I didn't ask the correct question. Say I have an ATTY and it's built to 2.0 ohms and with the setup here I set the voltage to 3.5v, would I be vaping at 6.125 watts? I guess I'm asking what would the chip do at this point. Likewise (I know I shouldn't do it but it's just a question) if I build an Atty at .25 and set it to 5.5 would I vape at 121 pushing the chip or would it only give 110W as the specs say?

[Visus]

Yes 6 watts

Yes 121 watts


Section Output on the spec sheet
Most modules will exceed their spec sheet values but it may harm the module if done frequently.  We pulse them and that makes our use of them a little different.  If built proper, hypothetically it may last a few lifetimes pulsing at even 130watts or just a day,  using it where  it never turns off a continuous use at 130 watts maybe last a year or two or just a few minutes, thats hypothetically of course...

Its absolute maximum limit is ~32Amps ~176watts

Section input on the spec sheet
What is really  cool it will only ask the battery for 8-15amps to do 20 amps depending on input voltage like at 5v it will only ask the batteries for 13-15amps while output is at 20amps It will change due to battery power lowering and sag.

[CraigHB]

Your range of power is dependent on atomizer resistance and limited by the regulator.  So for example if you set up a voltage range of 3.5 to 6V;

• Using a 1 Ohm atomizer your minimal ouptut power is 12W (3.5V² divided by 1 Ohms).  Maixmal output is 36W (6V² divided by 1 Ohm).
• Using an atomizer of 1/2 Ohm, it's 25W to 72W.
• For a 1/4 Ohm atomizer, it's 49W to 144W, however, the regulator is limited to 110W so the highest voltage you could run with a 1/4 Ohm atomizer is 5.3V.

There's also the limitation of your battery.  Demand on the battery is output plus losses divided by lowest battery voltage.  That would be about 120W divided by 6V or about 20A.  To support maximal power output for the regulator, you need a battery than can handle a 20A drain.  However, maximal output current load for the regulator is 20A so you can also run into that limitation.  Output current at 5.3 Volts with a 1/4 Ohm atomzer is over 20A.

I think the reason you are confused is there are a number of limitations that come into play.  You have to look at which limitation occurs first.  For the regulator, you have a maximal demand of 110W or 20A, whichever comes first.  Then there's the voltage range which is dependant on the regulator and how you set things up.  Then you have atomizer resistance and the maximal drain the battery can support.  All of these factors have to be considered when looking at output range in terms of power, voltage, or current.

[Visus]

Now I am confused too.

When I read the data sheet it says its maximum input amp request is 15.85 at output 20A
It also says 32A is the absolute maximum current before shutting itself down.
Meh the 08100 says 50 watts is its maximum and I use it frequently at 70-80 watts have done 90watts no issues

What gives there

Meh' cannot get the right screenshot sizing

Page 3 Input
http://www.murata-ps.com/data/power/okl2-t20-w12.pdf

[CraigHB]

I have not studied the data sheet for this part, but if there's a stated maximum for input current, then that applies as well.  It further convolves calculation of output range, but that's how things go with electronics.  There's always a number of factors you have to consider.

In that case, maximal input power is going to be maximal input current of 15.85A times minumum battery voltage of 6V which is about 95W.  Less losses that brings maximal output power down to about 85W at minimal battery voltage.

You can typically exceed ratings to an extent, but you risk reliability doing that.  You may be able to fudge that maximal input current value somewhat.  However, absolute maximums stated in the data sheet are in fact absolute.  If you exceed those even by a tiny bit, the part will fry.  For optimal reliability, you should not exceed ratings.

[Visus]

Cool I was hoping I was reading that right,  I have said it in other places 

phew lol

Yeah their underrated specs are I figure for maximums in safety for the module and other electronics its connected with so it doesn't become a fused buss bar lol

So it does need those 2v above output to operate so unless using a 3s batt it will never exceed the boards specs.. woot

Lol aha most shoulda just wired a OKRt10 or Ti08100 if using 2s batts 

the fine print  big eyes overlook wanting that huge number..

3s batts FTW

[CraigHB]

Yes, another issue that comes into play is regulator "drop-out".  For dual series cells, ouput voltage can be rather close to input voltage.  In that case, regulator drop out can cause a limitation in output voltage range.  Step-down converters tend to have a lot of drop-out.  For example, a regulator with a drop-out of 1.5 Volts has a maximal output voltage of 4.5V with a minimal battery voltage of 6V which is the typical minimum with two series cells. 

You can resolve the drop-out issue quite nicely by using 3 series cells.   That also gives you the full output power range for the regulator since minimum there is 9V and at 16A max input current, that makes the full range of output power available.

It's actually pretty common for things to seemingly get out of hand when calculating maximums and minimums for circuit specifications.  It's something I've burned a lot of brain cells over at times.  There's even more factors like variations in temperature and manufacturing tolerances that have to be considered.  It all gets quite complex when you want to accurately predict the capabilities of a circuit.  However, most of the time you can just neglect those more subtle factors to get a good enough idea.

[BFBCAcid]

Thanks to both of you this is fantastic information and great tech talk for others that may want to know. Thanks again.

[Thearlaich1965]

Just getting back to the forum and found this thread. I'm anxious to read it from beginning to end.

[joshgg81]

Ok hi im new here   wanted more power so Im building my own.  Im reciving the positive logic version of the okl2-t20 . I have a few questions  1. As I read earlier with this version I can not do a low voltage cut off   
                    2. I would like to do an on board pass through charger with this mod  and was wondering what would be best to use and how to wire it in.

       Thanks

[BFBCAcid]

Josh,
You can do a low voltage cutoff by selecting the proper Zener for you application my understand (Could be wrong) is that if you want a cutoff at 6.2 volts the you need a 5.5 Zener? Read the entire thread here and I think you will find it. I believe it talks about Zener (5.5) + .7 or .6 something to that effect gives you a cutoff of 6.2 or 6.1 respectively.

Now for my question anytime the top of my P-FET (MOSFET) touched the outside of the box it blows? Isn't that hole supposed to be attached to ground? And if do being my box is ground is that a problem? Any help is appreciated.

[mamu]

Ok hi im new here   wanted more power so Im building my own.  Im reciving the positive logic version of the okl2-t20 . I have a few questions  1. As I read earlier with this version I can not do a low voltage cut off   
                    2. I would like to do an on board pass through charger with this mod  and was wondering what would be best to use and how to wire it in.

       Thanks

I had the positive logic 12A OKL2 and not the positive logic 20A OKL2 and couldn't get a voltage reading from the zener as I had breadboarded it, but from what I've read from other modders working with the positive logic OKL2 20A you can add a zener and wire it exactly like the Raptor 20A or OKR-T10 wiring.

So try that and let us know if it works - put the pull-down resistor across on/off control and ground, then do the remaining wiring for on/off control and Vin like with the Raptor 20A or OKR-T10.

It takes special wiring to do a pass through with series batts, not as simple as with parallel batts.

[mamu]

Josh,
You can do a low voltage cutoff by selecting the proper Zener for you application my understand (Could be wrong) is that if you want a cutoff at 6.2 volts the you need a 5.5 Zener? Read the entire thread here and I think you will find it. I believe it talks about Zener (5.5) + .7 or .6 something to that effect gives you a cutoff of 6.2 or 6.1 respectively.

Now for my question anytime the top of my P-FET (MOSFET) touched the outside of the box it blows? Isn't that hole supposed to be attached to ground? And if do being my box is ground is that a problem? Any help is appreciated.

He's referring to the positive logic version, not the negative logic version I had worked with and a diagram for.

The metal tab on the back of the mosfet is also Drain (and is directly connected internally to the middle leg or whichever leg of the mosfet is Drain) - for reverse polarity wiring, Drain is connected to + batt. Absolutely isolate that tab from any metal touching it or any negative connection.

[joshgg81]

Ok awsome I will give that a shot and let youhow it turns out thanks alot

[CraigHB]

The metal tab on the back of the mosfet is also Drain (and is directly connected internally to the middle leg or whichever leg of the mosfet is Drain)

Check that in the part's data sheet, came across a PMOS recently where the exposed die (metal pad) was on the source.  It was a Texas Instruments part.  Almost screwed up on that, was just about to send a board off to the fab and then realized it was different on that one. 

That metal pad is actually what the chip is mounted to.  It's the pin that's tied to it, not the other way around.  There's a metal pad like that on either side of the source-drain channel that makes the connection.  They can expose either one for heat sinking.  Usually it's the drain, but it doesn't have to be. 

[mamu]

I assumed that he is using the p-fet most modders are using with the Raptor for reverse polarity - SUP75P03-07



I've switched from using that one to a smaller d-pak size p-fet...

[BFBCAcid]

Thank you for your response. I may be moving to the PAK as well.

[BFBCAcid]

Sorry to keep asking questions but I have a strange issue that I thought someone may be able to help with. I've been vaping my mod with no issues for a few weeks. One day I was vaping and noticed that when I turn the POT all the way up I was only getting a reading of 2.x volts. If I turned all the way down I was  3.5 like expected. So I took the atty off and measured it with a meter and sure enough I was getting 5.5 at high and 3.5 at low when I adjusted the POT. So I assume under load something is going on. I checked almost all components and they seem ok. My guess is that it is somewhere between the Trim (Board) connection, 1.43K Resistor and the pot or at the 510, but I am new so guessing is not a good thing. Any help on where to look would be appreciated.

Thank Again.

[BFBCAcid]

So I figured out my problem and wanted to pass the info along. I used the below Battery Holders in my mod and they seem to be dropping voltage like crazy not providing adequate voltage to the chip at high voltages (5.5) with low Ohm builds (.3). Even though I cut the cheap wire at the terminals and went with 18G wire from the battery box to the fuse / chip.

Now for my next questions. What are you all using for a battery tray so I can test something different in my setup.

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2146231_-1

[Breaktru]

Keystone holders are best.
You have loses w/ the holder that you have. It is especially noticeable as the amperage demand increases.

See: Battery holder contact resistance measurements

[BFBCAcid]

Thanks Breaktru, Off to the web I go.

THank You...... As always

[bob salter]

I inadvertently bought the positive logic board. I know how to fix the switch wiring. I'm using lipo batteries so don't need the pfet. Is there any way to add uvco to it?

Bob

[mamu]

For low voltage cutoff using a zener diode, wire the positive logic Vin and on/off control like the Raptor and OKR-T10 are wired.  I haven't tested this, but from what I'm hearing this is working for those who have the positive logic OKL2-20.

Also, for lipo batts, use a 6.2v or 6.4v zener.

[bob salter]

brilliant thank you. Will report back when completed

Bob

[nicvape]

Hello.
First I want to thank Mamu for this post . It is very helpfull.
 And second , I have breadboaded my OKL2 and every seems to be ok with no load ( 3.58 V min and 5.55 V Max).
But when I load the output , I have a huge volt drop ( almost 2 V !!!)
Sense + is on Vout and Sense - on Gnd
I don't know if the poor quality of my breadboard can be involved or if it is something else . I am a little lost.

Please excuse me if my english is not correct, it's not my native language

[DireHavok]

Ok not sure if I damaged chip. I have wired to the mamu diagram, less pfet and nfet. I did however wire pos sense to vin not vout. Remote is not activating output. If 20k res is removed I have fluctuating output...no idea if damage has been done...I have 2 more chips gonna re try...

Is the nfet needed or is that just for master switch?

**EDIT**  I have the w12n2-c which if not mistaken is a negative logic..and guessing remote lead needs to be moved to ground instead of Vin

[mamu]

Ok not sure if I damaged chip. I have wired to the mamu diagram, less pfet and nfet. I did however wire pos sense to vin not vout. Remote is not activating output. If 20k res is removed I have fluctuating output...no idea if damage has been done...I have 2 more chips gonna re try...

Is the nfet needed or is that just for master switch?

**EDIT**  I have the w12n2-c which if not mistaken is a negative logic..and guessing remote lead needs to be moved to ground instead of Vin

Need the N-FET if you want to use a zener for low volt cutoff.  Without the N-FET you cannot use a zener.  If not using the N-FET, wire one leg of the switch to on/off and the other leg to ground.

You cannot wire +Sense to Vin and expect the converter to work correctly.  The Sense pins are for supplying the converter feedback for output voltage, not input voltage.  Plus +Sense is internally tied to Vout so you've essentially made a direct connection between Vin and Vout by hooking +Sense to Vin.  I just don't understand why you would do that.

[mamu]

Hello.
First I want to thank Mamu for this post . It is very helpfull.
 And second , I have breadboaded my OKL2 and every seems to be ok with no load ( 3.58 V min and 5.55 V Max).
But when I load the output , I have a huge volt drop ( almost 2 V !!!)
Sense + is on Vout and Sense - on Gnd
I don't know if the poor quality of my breadboard can be involved or if it is something else . I am a little lost.

Please excuse me if my english is not correct, it's not my native language

Yes, it could be the breadboard.  Been there done that lol.

But it could also be the batt contacts, high internal resistance of the batts, inefficient input/output wiring, high amp load - anything that adds high resistance to the circuit.

[DireHavok]

Need the N-FET if you want to use a zener for low volt cutoff.  Without the N-FET you cannot use a zener.  If not using the N-FET, wire one leg of the switch to on/off and the other leg to ground.

You cannot wire +Sense to Vin and expect the converter to work correctly.  The Sense pins are for supplying the converter feedback for output voltage, not input voltage.  Plus +Sense is internally tied to Vout so you've essentially made a direct connection between Vin and Vout by hooking +Sense to Vin.  I just don't understand why you would do that.

Wiring the sense wrong was seeing wrong location...stupid mistake...I have several nfets just need small board to use it.  Why is zener not usable for on/off? Is it because its a negative logic chip

[nicvape]

Yes, it could be the breadboard.  Been there done that lol.

But it could also be the batt contacts, high internal resistance of the batts, inefficient input/output wiring, high amp load - anything that adds high resistance to the circuit.

Ok. Thanks for your answer. I'm waiting for my battery sled from vape3D and I'll optimize the position of components and the length of wires

[screwfunk]

Quick question for Mamu or anyone else with the know how. I cannot source the 1.43k resistor locally. They have everything else around it, 1.3k, 1.5k but no 1.43k. Is there anything I can do to change this or use something else in its place?

Sam

[wa9w00d]

Hi Sam,  You could put a 30k in parallel with that 1.5K.  Get you pretty close.

Wayne

[mamu]

Quick question for Mamu or anyone else with the know how. I cannot source the 1.43k resistor locally. They have everything else around it, 1.3k, 1.5k but no 1.43k. Is there anything I can do to change this or use something else in its place?

Sam

1.3K would give 6V output max and 1.5K would give ~5.2V output max.  Both are close enough to the converter max specs and would be ok, but if using the 1.3K, either don't exceed 5.5V max output or don't exceed 20A, 110W.

[wicked_tattoo]

I have been trying to get a build going with this chip for 3 days now.  I went and bought a breadboard to see if I can trouble shoot it that way. I got it all rewired and it now hums when it gets power? I am using the Mamu guide but trying to first get it to function without all the safety (similar to a HexOhm) just to see what I can make happen. I am really not sure what I am doing wrong. Any suggestions on how to set something up similar to that type of build? Thanks all

So no reverse polarity protection, no caps, just a n-fet and a 1.43k resistor for the pot.

[wicked_tattoo]

Anyone?

[Breaktru]

I have been trying to get a build going with this chip for 3 days now.  I went and bought a breadboard to see if I can trouble shoot it that way. I got it all rewired and it now hums when it gets power? I am using the Mamu guide but trying to first get it to function without all the safety (similar to a HexOhm) just to see what I can make happen. I am really not sure what I am doing wrong. Any suggestions on how to set something up similar to that type of build? Thanks all

So no reverse polarity protection, no caps, just a n-fet and a 1.43k resistor for the pot.

Which version of the OKL2 are you using? OKL2-T/20-W12N2-C or OKL2-T/20-W12P2-C
How many series batts are you using? 2 or 3. Are your batteries up to the task?
Is the battery sled and connections okay?
What resistance coil and output voltage are you using?
Have you measured battery voltage at Vin with the fire button pressed under load?

[mamu]

A humming/buzzing sound indicates the converter is being overloaded/overworked.  Could be from a too low ohm coil build, could be output voltage set too high for the coil you're trying to use, could be source volts/current not adequate, could be high circuit resistance interference.

Here's a very very basic wiring guide for the OKL2-T20 negative logic version...

[zotek]

what is n-fet for ? is it to avoid battery for draining when box mod is unuse? thanks

[mamu]

what is n-fet for ? is it to avoid battery for draining when box mod is unuse? thanks

For the OKL2-T20, the N-FET is used as a switch/driver for the on/off control plus convert this negative logic board to positive logic in order to be able to use a zener diode for low voltage cutoff.

[zotek]

can i use zener with out it and switch? thanks

[mamu]

can i use zener with out it and switch? thanks

No, you cannot use a zener without the N-FET for the negative logic version.

[zotek]

i dont get this one 4x 47uF 16v output caps in parallel (GRM32ER61C476ME15L)

that is this for? thanks

[LeeM]

can anyone please help me out with wiring a switch on a positive board rather than the negative?

[LeeM]

A humming/buzzing sound indicates the converter is being overloaded/overworked.  Could be from a too low ohm coil build, could be output voltage set too high for the coil you're trying to use, could be source volts/current not adequate, could be high circuit resistance interference.

Here's a very very basic wiring guide for the OKL2-T20 negative logic version...

carried on reading, and if i have the positive board could i use this a basic diagram but rather than wiring the switch to ground i wire it to battery positive?

[mamu]

LeeM - wire the positive board just like the Raptor 20A, except keep the same trim resistor and POT as for the negative logic version.

[wallie88]

I just got a okl t20.  I've  put it together and it is autofiring. I really don't  know what I'm doing, I'm just trying to fallow along as best as I can. I know it's hard to say without any info but if any of you have to guess what do you think is the problem? Is i have the 20k resistor on 1 and 2.