How-To: Add 7135 chips to a Driver Board (Stacking)

Thats great Ohaya! :beer:

A good thing to note for all us newbies who might encounter the same thing in one of our future mods. :slight_smile:

Rufus and Nightbird,

Believe me, it’s a relief. I was starting to think that there was something inherently wrong about the 7135 mods, but really, shorting that diode, and also, that old hand-drawn diagram from relic that I linked in post #202 was what did the tricks. Once both of those were in place, it was more eliminating the possibilities and tracking down the short (which wasn’t exactly in the most obvious place).

Now that I have this one board working with the additional 7135s, which was more of an experiment to test things out for myself, I’ll feel a lot better doing stacking mods for other lights.

Thanks!

Jim

Yup! That schematic also helped me in understanding the driver. That’s the one I use on my DIY driver.
It would be great if we have a database of schematics for each driver! :beer:

Hi,

A new, related question:

On this last board, I decided to stack the 7135s on the spring side of the board, whereas on an earlier board, I had stacked the 7135s on the non-spring side.

I know that I need to remove the small original spring and put another, conical one, inverted, instead.

This driver is going into an Ultrafire S5, which is a small tube-style 18650 light:

The way that the head is arranged, originally, there was a reflector, a tiny pill with the emitter and driver, and that slid into the head. There was small circular wire ring that goes behind the driver, and then a retaining ring screws in behind all of that and pushes everything up to the front of the light.

When the retaining ring is screwed in, it touches that circular wire ring, which then contacts the outer ground ring, and that’s ow the path to ground is made.

In my case, I replaced the reflector and emitter with a 3up optic and a 3up star with 3xXP-G2 emitters and the 7135 based driver.

The thing is, with 7135s stacked on the spring side, when the retaining ring is screwed in, the 1st thing (and only thing, really) that it presses against are the 7135s, so it never gets to touch the ground ring on the spring side of the driver :(!

So, in this situation, how can I get the retaining ring to contact the ground ring/negative on the spring side of the board?

What would/do you guys do in this kind of situation?

Thanks,
Jim

EDIT: I kind of gave up on this driver (with 7135s stacked on the spring side) with this light. I found another problem, where the spring would bend over and touch the retaining ring, causing a straight short from battery positive to battery negative, so I think that the driver is not safe in this light.

So, I added a 4th 7135 to the 1st board, and put that into the light, and it’s ok now. The 1st board now has 4 7135 (380mA) on the pill side, and one of the “partition boards” from FT soldered to the original tiny spring, and then a spring on the other side of the partition board for the battery +.

Thought I would add my 2 cents. After adding way too many 7135s this past week (almost 100), I've found that soldering on the first piggybacked chip gets really easy after a while. Get it lined up, touch iron to 7135 on board for about 1 second, touch pin on piggybacked 7135 and drag up.

Where it was a lot harder was doing the double stacked 7135s... I couldn't figure out why sometimes I could get it to bridge while other times I couldn't, and it seemed like the more I did the worse I was getting! On one board I got so frustrated that I had to just walk away from it for a while. I tried three different types of solder... more flux... nothing was working. Well, turns out that what I needed to do was walk away from it for a while! The key is not letting the 7135s get too hot; if they don't suck out enough heat fast enough you can't bridge the gap. So when I was getting more practice and working faster I was actually working against myself. Now I start multiple 7135s and move around the board when I'm double stacking so that the next pin/chip has cooled down when I come back to it to bridge the next pin.

Hope that makes sense... you all probably know this stuff and it made total sense to me after I realized what was going on but I just thought I would share.

A quick word of appreciation to the OP and others that have chimed in with helpful info in this thread. As a relative soldering noob, I was pretty intimidated by the idea of stacking, but this weekend I did a zener diode mod and stacking for some floody MT-G2 goodness.

It actually went way more smoothly than I could have ever expected, so if anyone’s sitting on the fence about giving this a try, I’d say “go for it!”.

Forgive me for asking if this has been explained already but I skimmed through this thread and could not find the answer… probably because it’s a beginner question, even for a beginner :slight_smile:

If I have a driver board with 8 x 380mAh chips and add one 380mAh chip I will get a total of 3420mAh when running on 100% mode, that part I get…
But how does it affect the other modes? The driver I would be adding to has specified 5% as low mode. Does the 5% low mode utilize all chips and draw 5% of them all (making it brighter with an added chip), or does the 5% utilize only one chip and adding one chip to the driver may or may not affect the 5% mode depending on which chip gets the new one added on top of it?

And a theoretical question: If I have a driver with 11 x 380mAh chips and have a programmed mode so output is for example 1500mAh, would there be a noticeable difference in run time compared to a driver with 8 x 380Mah chips running at the same 1500mAh current? Is there a loss in efficiency by having more chips on board?

Ok - 5% is 5% of the total amp limitation of the 7135's. The 7135's cannot be individually controlled on Nanjg or QLite drivers. 1500 mAh is an amount of energy, like in a battery, not a current, so not sure what you mean. A programmed mode in a Nanjg or Qlite cannot be for a specific amp limit, but represents a percentage based on PWM's. Typically with 7135 based drivers, high mode is a true 100%, while medium and low modes are implemented using PWM's. PWM is usually a very fast alternating ON/OFF, where 50% represents the LED on at 100% level for 50% of the time, and 25% means it's lit up at a 100% level for just 25% of the time, but flickers at a high rate where normally you can not perceive it's occurring. The higher the PWM rate, the less noticeable it will be. If you shine a light on low or medium mode at a ceiling fan for example, you can probably notice the flicker.

The reason of why you can only drive the LED at 100% and why PWM's is used is sheer cost and space savings to fit all these components on a very small board for a very low cost.

Also to clarify, 7135's only limit the current (amperage), they do not control or regulate the current at the summation value of the 7135's. So if your light and battery reach's the 7135's total in current, for example 3.04A, then that's the best you can do, but as the cell depletes it loses voltage, which results in loss of amperage, so you could end up at a lower amperage level, like 1-2 amps, when the cell is nearly depleted.

Hope this helps - not sure of your level of understanding these issues...

Oh I see. All chips are always used to 100%, but it’s the frequency that determines how bright the light appears. Makes sense.

My bad. I meant 1500 mA as in 1,5A current… But that question is irrelevant now as I understand that the driver will be running at it’s max capacity no matter what mode, it’s just the frequency that changes with the modes. Thanks for the explanation.

Yes - effectively, PWM's act as partial power - it even fools the DMM's when measuring amperage. It's a real simple way to address the problem, specially since the PIC's have the PWM support built in - real easy to program.

So I try put into this simpler way: Adding extra 7135 does increase the current in lower modes as well.

Is that correct?

Yes, once you max out the capability of the cell(s) you won’t get more current on high from adding chips but low and medium total outputs will increase. 1.5A is a poor example since many cells are capable of more than this. A good example might be a Sanyo protected 14500 with a max of 2A with a 15/100 driver and 5-6 chips 2.1-2.2A (say 2A for sake if ease) 15% of 2A is 300mA or 50mA per chip. If you were to add 2 more chips you might not get an additional 700mA from high but you would get (2 x 50mA) more on low.

Thanks Rufusbduck and Tom E. Now this explains why the moonlight mode of my Qlite driver looks brighter after I added four 7135 chips on it.

I’ve finally tried to do chip stacking and it works very well with flux and bending the feet of the chips. I’ve modified a Nanjg 1.4A to 2.8A and put it in a P60 dropin with an XM-L2. Output was fine for 10 minutes until it dropped to single lumen levels. The three different levels were visibly separated but very low. Have I destroyed the chips/driver?

Thanks relic38,

Just followed your tips, and added 3 chips..

I used these Goot Heat Clips, and they have definitely made this little mod a way lot easier.

the springs are rather stiff, abut will hold the small parts in position even better.. Now you`ll have 2 free hands again to solder.

little pricey at amazon, but worth the money, especially if you can find them for cheaper! great for shaky hands!

Just a suggestion, I use tabbing wire for a lot of this. This is the pre-tinned flat copper wire used on solar panels, not the tiny stuff but the “Bus” style that handles more current. The plus side is all you have to do is touch it with a soldering iron to make it stick. Wrap a small piece on the edge of a driver board tack it on both edges, instant ground. Reflector contacting the MCPB board? Tack small pieces to the contacts and solder the driver wires to the underside. Works great.

Links? Pictures?

Hello,

I have connected the 7135 chips, but they still not work!
What I do wrong?

Thanks

Photobucket changed to a pay system, and I put these on there. I have requests to update this thread, but unfortunately I do not have time, sorry.

@relic38 If you send me the picture files I can put them on.
We need to preserve BLF history :student: .