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

Using a vise instead of a helping hand is a good tip! I’ll have to try that.

I don’t know if it’s the same with all of the 3.04A drivers, but with the ones from IS, it’s hard to tell where the emitter leads are soldered to, so I’ve been trying to avoid removing the leads. They kind of look like they’re solder to a pad that’s connected to one of the IC pins.

On a previous board, I had to solder on new leads (26AWG), because one of them got squashed when I put the driver into the head of a light (S5) I was modding. I just kind of “guessed” which soldered area the leads were soldered to, but it seemed to work.

Since the chips are all in parallel you can solder led- to any of the 7135 output pins. Led + has its own pad next to the mcu input polarity diode but could be soldered to the battery + pad if for some reason you want a really thick wire and can solder to the other side of the board.

BTW Tom, that driver in the pics I had is another IS 3.04A board. I had it hooked up to a bench supply, and the supply was reading 3.4 amps, and the emitter current using a clamp meter was actually higher that that, like 3.5 amps. I guess the difference between the bench supply readin and the clamp meter could be due to non-calibration.


I added a 3rd 7135, but after that, it looks liike max current has gone down, to about 1.52 amps? I’ve checked the solder joints and all look ok. Is this a symptom of one or more of the 7135s going bad?

I have another same board, unmodified, and used the same setup, and shows 3 amps on high with the same XM-L2 emitter.

Maybe your battery can’t supply the needed current and it shift to a lower mode?
How about using a bench power supply? I got 5.04A just a while ago on my driver test. :beer:

Using my DIY bench power supply and DIY driver with 15x7135 I’m now getting 5.04A!
Placed the driver on a P60 pill and modified VBat- connection. I still need to improve my driver to emitter wirings similar to HKJ. :beer:

I am using a bench supply, rated at 5 amp/30V.

I had the same problem with my Nanjg drivers on my Convoy C8. The increase in tail cap current seem to be diminishing every time I add a new 7135. I wanted to ask the same question here in this thread but decided that I should seek the solution myself.

Yesterday, I made a new set of lead wires for my DMM, copying what many here in BLF did in getting the current readings of their flashlights. I used about a foot long (per color) of AWG 16 Automotive Wires, 2 Banana Plugs and 2 Alligator Clamps. When I used it to get the current readings, I was astonished with the results:

1) The LED current reading of my K40 (with 4 R100s added in parallel) became 5060 mA when the highest I could get using the stock lead wires of my DMM was only 3040 mA;
2) The LED current reading of my Small Sun T08 (direct-wired) became 5377 mA (yes, higher than my K40 which explains why it has a brighter beam) from the 2912 mA reading using stock lead wires;
3) The tail cap current reading of my Convoy C8 (with 12x 7135s) became 4169 mA from the 3012 mA reading using stock lead wires.

I guess changing the lead wires is worth a try. :slight_smile:

+1 x 10
I have a Skyray Kung 4 xml’s that I modded using 4-2800ma amc7135 boards for a total of 32 amc7135 ic’s. The tail cap reading with stock leads from a fluke 87V was about 6 amps. Changed the fluke leads to some short 16AWG silicone wire with banana plugs soldered in. I get a reading of 9+ amps now with partially charged batteries. Hoping for at least 10amps fully charged. So yes the leads size and length can make a huge difference in correct tail cap readings even if they are quality leads.

Are you all talking about the leads from my bench supply to the driver? For the positive, I’m using some short (about 12”) lead that I made using 20AWG stranded wire, connecting the power supply to the positive of the driver. I am using a switch on the negative lead, so for the negative, I have power supply => a tailcap switch => the negative ring of the driver.

I’ll try to cut down/improve the path on negative lead, and see if that makes a difference, but the reason I have the switch on there is that I had trouble getting the driver to switch to high mode.

Great work everyone with the stacking! I like the idea with the solid copper wire, will have to try it.
I will look into moving the pics from Photobucket, I think I am hitting my monthly limit.
Another thing I have noticed. 33/67 solder forms bridges much better than 40/60 solder. In the several times that I have tried both types, the former always seems to make things easier. I did everything in the OP with 40/60, but use only 33/67 now.

What I do to eliminate the switch resistance is after going to high mode, I bypass the switch using short AWG12 jumper.
Big difference in current/LED brightness!

One thing I found also is the multi-meter/probe resistance also affects the reading. By-passing the meter and using extra-polation I gained additional 200mA! I’m getting 5.2A on 15x7135.


I’m referring to the test lead wires of the DMM. I’m posting the picture of what I did:

Attached to my DMM are the test leads I made yesterday. They’re made of 1 foot long (per color) AWG 16 Automotive Wires, Alligator Clips and Banana Plugs (soldered directly to the AWG 16 wires). The pair at the left of my DMM are the stock test leads that came with it.

I have a slightly different setup. I don’t use a DMM (except for verification.

I am using a bench power supply, so I’m reading the current to the driver from the power supply display itself. For the emitter current, I have clamp meter, so no resistance on the driver-to-emitter side.

Anyway, I don’t think it’s my leads.

I tried another identical board, with original 8x7135s, and measured 3 amps (at the power supply).

I then added 2 7135s and measured 3.7 amps at the power supply.

I’m out of 7135s so I can’t add anymore. I tried harvesting one from the earlier driver, but I lost it (literally) somewhere.

I have some more coming in from FT. but those probably won’t come in until some time next week. I can try to harvest some more from the earlier board, but I’m kind of beat for now.

Easiest way I’ve learned to desolder chips is to cover all 3 pins with solder and when you melt that they all soften together then slide the chip off the boards.

Are these 380s?

Nightbird did you buy your 16 AWG wires from online store? If so do you mind letting me know where to buy this?

Also what is the banana clips?

No bibihang. I bought my AWG 16 wires from a local store. The banana plugs I used was from old test lead wires. Banana plugs are the the ends of your test lead wires that you insert into the DMM slots.

Then I’m afraid I don’t have the knowledge or skill yet to solve your problem with your 7135s. :slight_smile:

Thanks ,very useful !