Lexels driver compilation

Lexel, sorry to ask, as this may have been answered before!

Do you have 17-19mm drivers with Narsil (side switch) that can be used with 1 or 2 Li-Ion cells, for a single or triple emitter light?
I need something like that to mod the BlitzWolf BW-ET1 (AA/14500 light, side switch) either with a single emitter or triple!

Never modded an e-switch light before nor one to take 2 Li-Ion batteries, hence my doubts. Also…I tried to keep up with the drivers’ list but I’m too dumb to get it right :zipper_mouth_face: :person_facepalming:

I thank in advance for an answer on this :+1:

all my drivers can be run 2S
with 7135s I got 17 and 17-19mm with bigger copper rim

17mm I got newer drivers without AMCs that use a small FET instead for more realibility

Thanks for the answer Lexel!
The 17mm with FET is single sided?

I ask because the ideal diameter for the driver would be 18mm, but if it has 2 sides populated the battery tube won’t be able to make contact with the head and the driver, what will imply modding more things!

If the FET driver is single sided I can manage to make it work in some way !!

I never saw any problems with double sided drivers,
the parts simply are smaller than the spring and dont cover the tube rim

they are designed to fit battery tube lights


Yup, normally they don’t have issues, I’ve used them on other lights and they fit :wink:
But the “anatomy” of this light makes them harder to fit while screwing the tube. This is the original driver and the battery tube (more driver details here) :

As you see, the “bottom” of the driver is “clean”, so the tube makes contact with it and screws in completely.
Using a double sided driver (17mm, from you) you can see the gap it generates.
I explained myself wrongly, as the driver fits the hole, but the 7135 chips hinder the screwing in! Hence my question about being single or double sided!

I guess if it is double sided, it won’t fit :frowning:

there is a simple solution, called belt or wheel sander
simply shorten the tube a bit

the gap does not affect water tightness or so its a minorcosmetic thing, the light could have need that way originally

I am no expert rewriting the 2 Channel firmware to match 3 channel pinout its simply not the same channels on same pins
on older 30mm I had made pads to solder to reroute the pinout as I failed trying to program it

also that driver has a 2. board vertically attached to it likely for switch, not easy to handle

Yeah, I thought about that, filing or sanding the top interior of the tube. There is a small millimetric difference between the tube diameter and the driver diameter (the longest distance between the 7135 chips), so I may try that!

My only “fear” is that removing the anodizing will provoke any short-circuit if the tube touches any part of the chips or pads. I will do it tonight and check if sanding works to fit the driver. If so, I will PM you to order the driver.

This BlitzWolf light is built like a tank, hence the tubes are thick as hell :stuck_out_tongue:

So, I tried and filed the tube, and it happens that the chips came to fit, but on the interior (towards the head), the components got damaged due to pressure. The interior is not completely hollow, so it is almost impossible to not damage it… there is not a part on the driver that is entirely flat and without components, so it will get damaged anyway :frowning:

Thanks for the answers but I guess I will not be able to mod this light the way I was thinking :zipper_mouth_face:

so you mean the thick tube pushes the AMCs inwards or beareks the housings?
if you got a driver and the tube the tube should be always resing only on the AMC fins to make contact

The main problem here is thats the bore diameter for the cell is narrower than the AMCs housing outer diameter,
also some people have filed carefully the AMCs housing on the edges to make the diameter smaller

You dont need much force on the tube, likely you pushed it far harder than nessesary or good

I have seen people simply cut a solid strand copper wire and made a circle around the AMC fins that is higher a little than the housing, so no pressure on it applied

on request of a 3 people I finally made this one
the BLF development cost will add 10€ per board for first 12 drivers, not sure if I will ever sell that many

also played a bit with fancy copper in Silk markings for 3D effect
the copper inside silk should look good on white boards I prefer


Design highlights


- thermal viases same as the SD75 (a lot of work pathing those from a bigh block into the shapes needed)

- programming port

- optimised ground routing for all signal components to reduce noise (first made in MF04S/MT09R drivers of later revisions after LDO tended to freak out sometimes on HT07S driver of early revision)

  • LVP voltage divider with added noise filtering (first made in MF04S/MT09R drivers of later revisions)

introduced new design stuff

- customized rounded pads on resistors and most other parts (manually adding 28 points per pad with calculated values from Excel table —> very time intensive for many footprints I have)

- customized FET footprint

- text following the round driver shape (its all manually done no feature in the program)

- slot in board for switch board

- copper in silkscreen text for 3 D effect

- perfectly on a circle aligned rim viases, made as symetrical pattern instead manually placing each via (could be multiple rings like the BLF lantern has

- FET diode and inductor rotated and moved for more efficient pattern and smalöler switching node copper area

Okay, Lexel, i’m gonna save some money so i can place an order of probably 3 drivers.

Nice stuff. European prices unfortunately… :wink:

Why did you use so many vias? This will greatly increase fabrication cost and decrease board strength, and will not improve thermal conductiveness to the shell of the flashlight. Even if you use oshpark for fabrication, they may suspect something odd and request removal of via since this is unnecessary and increases tooling/cost and manufacture time significantly.

just compare such a board to one without those viases yourself, it conducts heat a lot better
I tested it myself with IR camera

if its not really nessesary on this build anyway it keeps components cooler

There is no tooling costs or so
Tooling costs ect. come to play if you order n-thousand boards for minimal costs
I oder 10 100cm² boards for 17.8$ with ENIG

Oshparks ships you 12mm driver for below 1$ internationally with free shipping,
they are simply so expensive per square inch they can easily compensate such orders they pay on top or boards with a lot tooling work

there is no relevant mechanical weakening, the board gets pressed on outer diameter, no tension in the middle

The main heat is dissipated by copper plan conduction radially on the copper planes. As a result, vias help in conduction of heat away from one layer and spreading them across more layer, especially applicable to multi-layer board with internal ground/power plane. Specifically for your design, main heat dissipation is by surface conduction to air, and then to what i presume to be the perimeter which connects to flashlight body. By adding so many via, the top-to-bottom heat conduction is very good, but at the cost of in-layer radial heat conduction because your holes remove something like half of surface copper! Overall with the additional copper, I think it’s a bit of a toss-up, but the benefit is not as much as you think, at significant fabrication cost and structural cost. 1/20th of the number of vias is more than sufficient for your application.

the majority of heat dissipated in most flashlight is in the led, so if there is a very good thermal bond between led and body, assuming body doesn’t dissipate heat well because most flashlight body have no fin or active cooling, it is even possible for the temperature near the head of the flashlight to become very hot. such, the main heat-sink of the driver pcb is now not effective much as a heatsink.

IT looks like your board connects to some spring to the battery, so mechanical strength is quite important since your PCB diameter is big. there is a lot of force that can be exerted on the middle because only the outside is supported. even if the PCBdont break, it can flex which can cause failure of solder joints on the other side of the pcb.

oshpark pcb is quite expensive compared to China pcb, so I think they can cover tooling cost. But if you fabricate this board at any other pcb plant, the prices will definitely be much higher if you ask for quote.

conclusion - my suggestion is that the vias be reduces for better pcb practices, and still be good performance. I appreciate your design so this is just my suggestion. Thank you for reading!

make a 20mm board with two 1oz copper planes and one with 0.35mm plated holes in a 0.55x0.48mm grit
put a 2512 3W resistor in the middle
clamp the outer 1.5mm bare copper ring between 2 aluminum plates that leave the inner PCB open or simply use a flashlight with retaining ring
measure the resistors temperature of both boards after 10 minute when its saturated

then talk again about sense and senseless of thermal viases


you forget that a via is a plated copper hole, so there is a lot copper inside the board also conducting heat radial, the thicker the board the more copper you add
even if you remove FR4 the copper conducts a lot more heat than the removed material

and you forget the main cooling comes from the bare copper rim of the driver touching the metal body,
getting the heat there is our goal and viases do it better
surface heat conduction to air is totally irrelevant inside a flashlight

you talk about removing half the surface copper this is totally right!
0.35mm plated hole removes 0.28mm copper circle in a 0.55x 0.48mm grit
so 0.12mm² copper removed inside a 0.264mm² area

but a via 0.35mm on a 1.6mm thick board adds about 5 times the copper you removed on surface inside the driver

calculate the copper inside a board

we remove 0.35mmx1.6mm FR4 this equals 0.31mm³ per via
FR4 thermal conductivity 0.25

solid surface copper board volume
Kupfer thermal conductivity 9355
so the copper planes in 1 oz conduct more than 1000 times the heat than the FR4 does
so we can simply ignore the FR4 at all in the thermal equasion

surface copper removed 0.35mm hole minus 2 times 35um copper

lets look at the internal copper added
internal copper added A=(0.35-0.035)*0.035*π=0.034mm²

lets calculate the copper difference between the added and removed copper
thermal conductivity gained after calculating lost surface copper and added internal copper

so in the end the via copper conducts 430 while the removed copper would conduct 80.5
this is more than 5 times more heat conduction based on the coppers volume, sure the hollow cylinder does not conduct as good as a solid plane but in the end its likely still 4 times better

Its nice you theorize about the viases, practically they work like 2 times better than without them

As said, conduction of heat to flashlight body can sometime be not as good as you imagine because powerful light (which require all those via anyway) likely has a very bright led, which make a lot of heat, so the local temperature near the ring around driver PCB can in some cases be quite warm, and thermal cooling by conduction may not be as good as you imagine. In event of efficient switching circuit on driver (versus linear), it is possible (at high led power) and high air temperature that the driver is cooler than the case.

As you mention, the bulk of copper is in the form of via, not in-plane copper. Adding holes to the in-plane copper significantly reduce in-plane thermal conduction (at the extent of the hole per area ratio). Therefore thermal conduction is not as good as you imagine. Immediate thermal sinking due to increased copper volume will help initially, but once thermal saturation occur, transmission is not as good as you imagine.

Overall I think adding so many via is necessary and not provide much benefit (which is fine), but this come at a cost of significantly longer fabrication time and structural rigidity and board flex (lead to component solder joint breaking), which I think is not a good trade-off to make for robust and strong flashlight.

Thank you for reading!

Seems simple:
For conducting heat more copper is better than less.

It's not simple, there is always an optimum number and size of vias for such designs; with too many vias close to heat source you are creating bottleneck and cutting "heat supply" via top/bottom copper layer for more distant vias, so they become useless.

not simple; ‘more copper’ is not always better, because where the copper is, is important. Many scenario:

- if the goal is to sink heat away from source by a good cooling source like heatsink, radiator etc, then having additional copper mass is not ideal. instead, you need to have lowest thermal resistance away from heatsource. one example is thermal pipe used in cpu, instead of big copper block.

- in the above pcb where so many vias a drilled, then the surface copper is significantly reduced creating poor thermal path in-plane. yes you get better thermal conductivity plane-to-plane in z-axis, but too many via will reduce effectiveness for in-plane conduction.

- as a result, to conduct heat away from source, you can put many via near source to conduct heat from top to bottom plane (or internal if it exist), then you want to then reduce via away from source to maximize in-plane thermal conduction to the heat sink (flashlight body)

- in addition, adding so many via will lead to significant structural integrity tradeoff, which i think is no want for flashlight where the middle of the pcb contact battery

however for fun and to look interesting, this design is ok. i just want to suggest improvement in term of engineering practice. thank you for consideration!

I have to agree in this with clientequator.
Moooore is not always better.