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

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relic38
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How-To: Add 7135 chips to a Driver Board (Stacking)

This is my first entry in my How-To series.  These are step-by-step instructions for tasks related to flashlight modding.  There are many different ways to do things, so I will show the methods I use that work for me.

This How-To will show how I add AMC7135 current regulator chips to a flashlight driver board.  Our desire to do this is to increase the output current to the emitter. J)

This isn't really a soldering how-to, so I assume that the reader already has basic soldering knowledge and skills.  There are many soldering tutorials on here and the rest of the internet.

Parts, tools, and supplies required:

  • 7135 based linear driver
  • one or more extra 7135 chips
  • soldering iron
  • helping hands
  • tweezers
  • magnifying loupe
  • solder
  • solder wick, for any solder related boo-boos

parts

Here is a close-up of the parts.  I had this driver kicking around.  This is a generic version of the NANJG and it's not good.  I harvested it for parts, but it's good enough for this How-To.

parts

 

The 7135 chip has three pins and a tab. 

Pin 1 is 'Out', where the cathode (negative) side of the LED is connected

Pin 2 is 'Gnd', which is connected to the tab, which will make things a little easier for us later

Pin 3 is Vcc, power for the chip itself.  Without power, it blocks all emitter current flow.  This is the pin that the driver controller (MCU) uses to control the output power.

Tab is 'Gnd', connected to Pin 2.  The tab is the main thermal extraction path for the chip, so it is important for it to be connected to something to pull heat away.

7135 top

On the bottom side, we can see how the tab and Pin 2 are connected:

7135 bottom

 

Start by placing the driver in the helping hands.  I'm adding a chip on top of the one on the right.

driver

I start by re-tinning the tab, pin 1, and pin 3.  This tends to make the process a littler smoother when making the first solder bridge.

tinning

Tinning makes freshens up the solder so it accepts new solder easier.

driver

Prepare your iron by loading up a healthy portion of solder.  Estimate enough to fill the void between the two tabs of the chips, maybe a little extra.  After the first couple of tries, estimating the amount is easier.

solder blob

Using tweezers, hold the new chip directly over the existing chip.

new chip

Use the soldering iron to apply the blob of solder into the space between the tabs.  Raise the soldering iron vertically to get the solder to move upward to the top chip.  You may need to take a few swipes in order to get it to stick.  Add some solder if it looks like there isn't enough.  Once it bridges align the chip before removing the iron.  Once aligned, remove the iron, wait for the solder to solidify, and the chip will stay in place.

tab soldered

Now we move to the pins:

pins

I hold the soldering iron vertically whenever possible.  This helps because we can extract the iron vertically.  Plase the tip of your solder right in between the two pins so it contacts the iron.  Melt enough to fill the gap, but too much could results in unwanted shorting to nearby pins or components.

iron on pin

There, the first one is done:

pin1 done

Now repeat for the other side.  And, we're done!  There's no need to solder the middle pin since the tab is connected to it.

done

Like any soldering task, there is some practice required.  You may not get it right the first few tries.  Just keep trying and you'll get it.  Do it enough and it becomes second nature.

Pretty soon you'll be building your very own 40 chip 7135 driver Wink

YH driver mod

Happy Modding and thanks for reading! searchID8936

 

 

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Edited by: relic38 on 03/31/2013 - 00:30
relic38
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Not sure why, but just in case.

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jakey
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Thanks now i think i could have a go Wink

let there b rock (i mean light)

gords1001
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nice guide, were building up some good info on here now :bigsmile:

Buwuve
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I do this a few times (not 40 times and your practice would be better as mine) and I like your pictures. It will help new members a lot Smile

Light up the darkness.

nitro
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Relic have u tried bending the legs ? Much easier

Another suggestion that would be good on this thread is if u post how many amps the driver will be, just for say u add 3 to 8 extra chips what would the driver be at for learning perpases ?

relic38
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Thanks everyone.
Nitro, I avoid bending the legs because the structure inside the chip itself is not designed to have the leads bent. The worst case is, you break off a pin. Most of the time you’ll be OK. However the stress could weaken the internal bond wire contact, leading to eventual failure. You might notice it as a flickering/varying output (intermittent) or not the current output you expected (disconnect).
For this reason, I do not recommend it. YMMV.

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Ouchyfoot
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Thanks relic. Your tutorial is clear as a bell. A picture is worth a thousand words. I find visuals really simplify a seemingly daunting task. I know I can do this, and I will do this!
Actually, the way you don’t bother bending the pins does make sense to me. It leaves them out in the open, and more accessible to the soldering tip, while keeping it away from the chip itself.

rdrfronty
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Thanks relic for the how too. I’ve tried this a few times with no success. I guess it’s mostly due to my hands not being steady enough. I mean your photos and instructions make it sound easy. But when the driver is the size of a dime and the 7135 chips are the size of a tiny ant – and you have to solder the ant sized chips individual legs – no way for me. And I have a good mechanical ability and aptitude. But this is a no-go for me.
My poor attempts make me appreciate the fine detail work many of you on this forum can do.

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thanks!!!!! this will be a big help for me being a first timer Smile

Would you mind keeping the wrong flashlight?
Best wish, May
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You’re welcome. Bending the pins does make soldering easier; if the pins stay connected to the chip.
I will do a few more of these How-To posts. The next one will be “Adding Copper Braid to Springs”. The pics are taken, I just need time for post and write-up.

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If your going to do copper braids, please show me where to get some, and the proper type. Is it the same as desoldering braid?

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Ouchyfoot wrote:
If your going to do copper braids, please show me where to get some, and the proper type. Is it the same as desoldering braid?

Yes, I use desoldering braid. Easily found on eBay, Amazon, Digikey. I use one of the more expensive brands, Soder-Wick by Chemtronics. I’ll provide a link in that post.

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timebndit
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as a new guy in this hobby II don’t really understand why you did it…yet, but I can say the tutorial shows how to it very well Smile

al

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So if I added three chips to 3.04A driver it would become…?

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Thanks Relic! Like this How to. Looking forward to your next ones!
My suggestion is to use the How to on the subject so it’s easy to search.
Like “How to Add a Copper Braid to Springs” Beer

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As posted:

Quote:
Our desire to do this is to increase the output current to the emitter. J)
Silly
In other words, increase the light output by giving the emitter more current.
Also, we rarely stop at just adding one Wink

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Not sure if these would interest people:

18x 7135

Those are 16x 7135 boards. 8 each side, 20mm in diameter. Each boards has a solder point for LED+, LED-, PWM and GND.

I also have 12x 7135 boards. 6 each side, 20mm in diameter. The difference is that the solder points for LED+, LED-, PWM and GND are much larger 1.5mm in diameter through holes, thus allowing for more robust wire. 

Both boards were designed for a project of mine but they can be used for many things obviously. Just saw this thread and thought people might like to know stuff like this is available Smile

- Matt

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Actually, I have some desoldering braid in the mail. It’s only 1.5mm though. I thought it might come in handy to span a gap between a driver and pill. I figured I could soak it in flux, wrap it around, heat it up and add solder. Whether its a good idea or not, I don’t know…who knows.

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Ouchyfoot wrote:
So if I added three chips to 3.04A driver it would become…?

If using the 350mA Regulator: 3 × 350mA = 1050mA, it will be 3050+1050 = 4100mA or 4.10A
If using the 380mA Regulator: 3 × 380mA = 1140mA, it will be 3050+1140 = 4190mA or 4.19A

Beer
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Can you stack a 380mA regulator on a 350mA regulator, or is that bad?

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nitro wrote:
http://img580.imageshack.us/img580/5301/img20130129171725.jpg Nice boards where did u get them ?

They're my own design. I'm waiting until my project is finished and then I plan on offering them to anyone who wants them (plus some other things that came about as a result of the work I did). I started out intending on using the 16x7135 boards but felt for my particular project they were too cramped, so redesigned them as 12x7135 boards. 

I might make a separate post about them actually. I'm probably going to give the prototype 16x boards away for free (provided the 'buyer' covers postage of course). I can't remember how many I have but it's only about 12 or so.

 

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Ouchyfoot wrote:
Actually, I have some desoldering braid in the mail. It’s only 1.5mm though. I thought it might come in handy to span a gap between a driver and pill. I figured I could soak it in flux, wrap it around, heat it up and add solder. Whether its a good idea or not, I don’t know…who knows.

Perfect size, that’s what I use. Plenty of current carrying capability. It’s usually got a layer of flux on it, so you might be able to skip that step.

Ouchyfoot wrote:
Can you stack a 380mA regulator on a 350mA regulator, or is that bad?

Yes, the two types have the same pinout, no issues with mixing them.

Mattaus, those are nice boards. Great for adding a lot of chips to a project. J)

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relic38
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Sending a letter to Canada is $1.65, up to 50g is $2.35… the 16x ones should fit flat in an envelope. I figure they are less than 2g each. I might be interested… thinking of where I’d use them…

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Mattaus
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relic38 wrote:
Sending a letter to Canada is $1.65, up to 50g is $2.35... the 16x ones should fit flat in an envelope. I figure they are less than 2g each. I might be interested... thinking of where I'd use them...

Not even worth covering postage. I'll see how many I have when I get home tonight and if you want them, they're yours....though if others are interested it'd be fair to share them around I guess.

relic38
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OK, sounds good. Let’s see how many we get. If all in one region, ship to one person and we can distribute from there.
Thanks. I still can’t think of a project for them yet, but I’m still thinking.

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Thanks relic38 for another thread on soldering chips onto one off these drivers. Now for my sook. There are plenty of well done threads on this mod which are all good and helpful to the point I still cant do it with the pins bent down. Now you come along putting bucket loads of these things on one driver with the pins pointing straight out. Seriously thanks ___________________________________________________________________________________________for rubbing my nose in it. Cry

 

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Hi MRsDNF, you’re welcome, glad to help. Silly
Soldering these little bits does take some practice, and I have had almost two decades of it. Do not be discouraged, keep at it.
Besides, $13 gets you 100 of these chips to practice with Wink

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Thanks relic!  You make it look so easy!  Then you get these things on front of you and they are TINY!  I've not yet got around to trying it myself, but I expect to butcher a few trying! 

-Garry

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