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

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ruffles
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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!”.


 

Mike C
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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 Smile

If I have a driver board with 8 × 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 × 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 × 380Mah chips running at the same 1500mAh current? Is there a loss in efficiency by having more chips on board?

Tom E
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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...

 

Mike C
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Tom E wrote:
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.

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

Tom E wrote:
1500 mAh is an amount of energy, like in a battery, not a current, so not sure what you mean.

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.
Tom E
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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.

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

Is that correct?

Rufusbduck
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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 × 50mA) more on low.

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bibihang
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Rufusbduck wrote:
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 × 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.
DanielM
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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?

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ChibiM
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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!

slotguy
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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.

ChibiM
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Links? Pictures?

fenno
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Hello,

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

Thanks

relic38
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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.

Welcome the night.

My Reviews   My Mods    http://budgetlightforum.com/search?

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

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