The sought after AMC 7135 board master/slave sandwich mod - an explanation

Flashlight Modding and DIY Parts
1

Hello,

I have been conversing with (cpf) techjunkie about the ever popular method of using multiple 7135 circuit boards as Master/Slaves in order to use multiple LEDs without having to go the series routine and have to use high voltage.

The following is a copy of the PMs between me and techjunkie. It's rather long and I hope it's clear enough as there is a lot of "quoting" in it, so read through and see if it helps. I did highlight all his replies in red.

1. Re: Everyman's Mod

Originally Posted by Old-Lumens

Hello,
I've seen some of your mods and they are fantastic. I do some modding too (mainly at BLF), but I am illiterate when it comes to electronics circuitry. I have questions and I just can't seem to "get it" when reading posts in the forums, about this circuit (Everymans)...

Justin,

The easiest way to explain it in layman's terms is to think of it as three flashlights in parallel, each with their own regulators, but all powered by the same set of batteries. Much like anything you plug into an outlet in your house runs in parallel to everything else in your house. Your TV, lamps and refrigerator all draw different amounts of current without changing the amount of power run through the other devices because individually, they are self regulated. The same thing is happening in the flashlight.

Each of the three regulators in my Everyman's Build is controlled by a single mode board that just happens to be on one of the regulators. The way that the mode board controls the three regulators at the same time is less like a light switch or dimmer switch that could control several chandeliers in your house at once, and more like a single remote control that would change the volume on three of the same TVs or stereos at once.

Originally Posted by Old-Lumens

I see how you have used the 3 XM-L emitters in parallel, but that's not really in parallel? because of the three boards? I still don't get it, since they still all have the same power lead aren't they still in parallel? If the boards are regulating, how does that control the voltage, since the boards are linear and only control amperage.

Also one board is the master and the others slave. Isn't that more of a load on the master than it is recommended? I mean, will it cause the board to burn out faster, with the extra draw pumping through it? If the amps are being drawn out of the master board isn't that three times it's limit feeding the other boards?

The way it's wired, 1 board + 1 LED makes 1 circuit. The three circuits are wired in parallel with each other. Each (sub)circuit is regulated by its own board. The regulation of those three individual sub circuits is controlled by a single mode board. Don't let the fact that the mode board is installed on one of the regulator boards confuse you. Technically, it's a fourth sub circuit that runs in parallel to the other three regulator+LED circuits.

Each regulator controls amperage by modifying the amount of resistance it applies to its individual circuit, which in turn selectively lowers the amount of voltage left to the rest of its circuit (the LED) to have the effect of regulating the amperage of its circuit. Less volts to the LED = less current drawn by the LED = less amperage.

Originally Posted by Old-Lumens

There are loads of multiple emitter mods I would like to do, but I will not use Li-ion and NiMHs are limiting due to the room needed to do series emitters. I would love to do the parallel thing, but is it as safe for the emitters as series is?

What is the limit of this circuit? 3-4-5-6 emitters? How many can be done together that way?

Because each regulator is individually controlling the current applied to each LED, it is just as safe as a series string. At the crux of it, that's the point of the design. There's practically no limit to the number of emitters that can be connected this way, but the obstacles are voltage sag of the batteries as the total current (amperage) drawn from them adds up, and also the limitations of the switch. The Mag switch is OK for up to ~10 Amps (I'm about to push it to 12A with a 4x version of the Everyman using 3.0A regulators instead of 2.8A regulators). Beyond that, you'd be best to have the switch only control a FET switch capable of higher loads.

Originally Posted by Old-Lumens

I would appreciate it if you could take the time to try to explain to me how your circuit works and how it remains safe and controlled in a simple way that an electronically challenged person might understand.

I know you must be very busy, so if you don't have time for my questions, I will understand.

Thanks in advance for your time,
Justin

My pleasure.

Thank you very much for the explanations.

A couple more questions about your drawing. It seems that not only the 8 pin controller has to be removed on each slave, but also the resistors at R1 & R2, is that correct? Also in your drawing I see what looks like a resistor crossing two pin sockets (where the controller was). Was that something you did and why?

Thank you very much. I would like to try to duplicate this mod, as there are a number of people asking on BLF, but not getting answers.
Also may I "quote" part of your replies at BLF, if I post a description of how the driver setup works?

Thank you once again,
Justin

Those are photos of KD sku S004338, which is the single mode version of the board. I think they bridge the two contacts where the 8 pin controller was just to connect the power input from the spring to the VDD inputs of the AMC7135 chips to power them. There also appears to be a 0ohm sense resistor near the LED+ contact that might also serve to bridge the Vin to the LED+. Neither was necessary the way I did it, because I already had excess multimode chips and simply opted to remove everything except the AMC7135s and wire Vbatt directly to the LEDs and the VDD out signal from the controller directly to a trace route connected in parallel to all the VDD contacts on the 8x7135 chips on each of the other two boards.

Go ahead and feel free to pass this info on to BLF. Just be careful not to misquote me and make me indirectly responsible for misinformation.

EDIT: 04/06/2011 - Added corrected photos and new information, copied from TJ in Post #38

Just saw this thread and want to point out that in both Old-Lumens drawing and my original drawing above, there's one important thing missing... the ground wires that connect the slave boards to ground. Without those, LEDs 2 and 3 won't light. Here's the modified drawing:

corrected slaved regulators config

Even better, here's a mod to the method above, whereby only the low current required to operate the micro controller goes through the switch, but not the high current for the LEDs. In this method, the regulators are operated by the mcu like a low current switch can be used to operate a FET or a solenoid switch. By doing this, the switch resistance is eliminated, thereby reducing parasitic resistance and increasing regulated runtime:

Better slaved regulator config with switch resistance bypassed

You can use any number of regulators and LEDs. The pic above shows 4-4, but 2-2 or 3-3 or even 5-5, 6-6, etc. would work the same way. Note that bypassing the switch to eliminate resistance is great for 3 cells or 4 weak cells, but I actually had to improve regulator heatsinking and add resistance back in when using 4 powerful cells and 4 tightly stacked regulators to avoid them overheating and throttling back.

------------------------------ END OF COPY --------------------------

Also, here is a photo showing which star to bridge for different modes. This only works on the board shown, as I know there are several variants floating around.

modes

Hopefully this will answer some questions for people. It did for me.

Thanks to techjunkie for taking the time to answer the questions and do it in such a direct manner.

Justin

2

Post is up now with the info

3

My question was for 2 boards, so u have to have 3 to do it.? I was under the impression 2 boards would be safer and still give me max output on a single cell 18650/26650? I’m a bit confused but enlightened ,I guess I’m looking a easy simply drawing say this is what u do ,lol
Also what size wire is preferred for wiring/sandwiching driver?
Thanks a lot for your help

4

I have never seen before specs for the 105C that start with Low, all start with High, for example 100%-30%-5%.

Also from all the specs I've seen the 4th Star should be 10% or 20% not 5%.

Is that Nanjg 105C flashed (custom) to start with low on all modes?

5

How many Amps can be drawn from 1 and 2 x 18650's respectively using this stacked driver?

6

Mine goes Low > Medium > High and I haven't soldered any stars! It came from shiningbeam if that helps

Thanks for the useful post

7

Thanks, Dan. I see, so it means that Shiningbeam may have ordered them to start with Low, since theirs star with Low.

Or....

Do you have the 105C, right? Because they also sell the 106 star-less model (still 8x7135), which is L-M-H.

8

Yup, it's a 105C, it has the stars and the text "105C" on it....

9

I would like to say a BIG thank you to both Old Lumens and techjunkie for this very informative discussion regarding paralleling boards for multi-XML mod. There are very few boards around that are both capable and reliable to drive a circuit described above. Until such time, this is a nice alternate for those of us who crave "big power".

It reminds me of the days when P7's were the "big boys" in town and 2.8A drivers were not quite mainstream.

10

Great info. Thanks.

11

Its great to see this info consolidated and explained well.

I'd never seen that last pic. And thank you for the red and black "wires". My mind works in red and black when thinking about electricity (which is why I avoid household electrical work :))

12

Ok, there are several versions of this board. I have seen at least five versions of the same basic 2.8A board. All of them appear to be different. It seems like each run has modifications on it. You will have to contact the supplier or vendor of your particular board to determine which star needs to be bridged and each version may be different as to high, med. low, strobe, etc. I do not have the information for each run of boards. If someone does, then please enlighten us with a list of each rev.

Also, I did not do a step by step, solder this to that, because I have not done this mod myself. As far a wire goes, I use the us awg standard for wire diameter, even though it is a very conservative chart. I use the column headed "Maximum amps for power transmission" column. I have never found a chart for LED emitters. There is also this chart for 12vdc automotive wiring and it might be closer to what we use.

13

In the pic below, the component highlighted isn't necessary, correct? Not the clearest explanation by techjunkie but I believe he said it wasn't important when you asked him why the other resistors were removed but this one in the center remained. Am I correct in my interpretation?

14

Madi05 - techjunkie states you use the number of boards you need like this, 1 board = 1 emitter. If you have one emitter, use one board and add a board for each emitter added. Remember these are linear boards and they control Amperage. Voltage is controlled by the Vf of the emitters, suffice to say that you only need One Li-ion or three NiMH batteries to supply this parallel setup. One Li-ion + 3.7vdc or 3 NiMH (in sereis)= 3.6vdc.

The Amperage will be the problem here. Short run time on lower amp rated batteries. There's a give & take to all of this. This lets you run 2 or three or more emitters with one Li-ion or 3 NiMHs (in series), but the price is short run time because the amperage is high.

If you did series instead of parallel, then you would need more batteries because the Voltage will be higher, but the Amperage stays the same.

Parallel - Amperage increases for each emitter in parallel.

Sreies - Voltage increases for each emitter in series.

Hope this helps, if not PM me and we can work it out.

15

Those boards are One mode boards from Kaidomain. The "resistor" shown is the sense resistor. It is stock on those boards and it is ok to leave them, or it can be removed. For the boards that already have the controller on them (multi mode boards), if you use them as slaves, then strip off the controller and all the resistors, so that only the AMC7135 chips are left on that side of the board.

Hope this helps.

16

Thanks for this! I'll be trying a 3 board sandwich for a Beamtech bt4000 once the boards come in. I'm sure the pictures will be a handy reference when it's time to wire them up.

17

You only use 1 Li-ion cell. You could use 2, but it will increase the voltage, not the amperage, so it does not help (unless you were to wire up 2 cells in parallel).

Parallel - more amps

Series - more voltage.

As far as how many amps? How many boards are you going to use? If you are using this board, then 2.8 Amps per each board. 1 board - 2.8 amps, 2 boards - 5.6 amps, 3 boards 8.4 amps.

In one of techjunkie's mods, he was using 3 AA NiMH cells and was getting 8.4 amps (i believe), I wouldn't want to do to that to poor old AA NiMHs. Very short run times and a lot of stress on the cells.

Li-ion? I do not know the limits of Li-ion, you have to ask for others to help with that. I do not think one 18650 would take 8.4 amps. That's why a lot of mods are done with NiMH, since they can take more abuse without going bad. I think a 26650 or 32650 would do well with this type of mod, but I'm not a Li-ion guy. I'm sure others will chime in with better answers.

18

Disclaimer - I am an amature modder. I am not an electronics guy, so take my answers with a grain of salt and if you have doubts, ask other menbers for confirmation. This board setup is new to me also, but I see how it works and I will be doing mods this way. For me, this is a way to do 3 XM-L U2 with 3 NimMH batteries. I can see doing one with 3 "C" or 3 "D" and with "D" LSD NiMH cells, I would have 10,000mah, so the amperage problem is solved.

Li-ion is like the White Buffalo to me. Something you hear about, but don't necessarily believe, so Li-ion questions should also be asked, to some of the wiser Li-ion using members here.

19

An IMR 18650 would handle 8.4A easily but for normal li-ion it's best not to exceed 2C. That's 2 times the rated capacity of the cell. For example 4.8A from a 2400mAh cell or 6.2A from a 3100mAh. If you use 2 cells in parallel you can double that. For example 12.4A from two 3100mAh cells.

HTH,

Tony

20

So u r saying I have to do 3 drivers to run 3 LEDs which will be 8.4 amps ,I’m only running one 26650 will that 8.4amps hurt my battery?
Also 14 wag wire is ok?
And I only ordered 2 3040ma because this all I thought I needed but I have 1 2280 the same driver jus the step below can I use it for my third with same effect or will it mess things up, I sure would hate to have to wait for another one :frowning:
Thanks so much u have helped me a whole lot understanding :slight_smile: I will pm u soon asu mentioned :wink: