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

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.

:beer:

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?
:beer:

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 !

Sorry, I forgot to mention that both the earlier and 2nd board were 3.04A boards from IS, so they had 8x7135 (380mA versions).

The 2 7135s that that I added to the 2nd board were the 350mA 7135s.

I ran out of the 380mA 7135s earlier (and now ran out of the 350mA ones also).

EDIT: I started harvesting 7135s from the 1st board, and got the 2nd one up to 4 amps (from the bench supply), and only left it on for a second or so, but then later, when I tried to power the driver+emitter up, it doesn’t work anymore :(.

I’ll be starting to diagnose after this…

Something I’ve been wondering about. I’ve been reading how everyone keeps getting higher current reading from their DMMs by upgrading to shorter, thicker wire. Wouldn’t the truest reading of your drivers output be if you were using leads of the exact same gauge as those on the driver and emitter wires?

Ouchy, see this related post.
Testing using the best possible setup will give you an idea on what current your driver can deliver. If you’re not getting the expected current then it must be something else (battery, switch, wires, heat …). :beer:

Hi,

So, I’ve visually inspected the board very carefully, both top and bottom, and I don’t see anything wrong. No solder bridges, no missing joints. Everything looked ok.

Putting the driver on the power supply, I am measure correct voltage when measuring voltage across the negative ring on the spring side and the + on the board.

When I apply power, and measure across the emitter, it’s showing like 0 - 0.02V.

The driver board appears to be dead, but I’m not sure what else to check?

Need pics to spot a problem. Otherwise can only assume toast. If the mcu is fried you can jumper from led+ to any Vdd pin and have a single mode regulated (high) board.

I realized that I should try to ohm between the Vdd pins and OUT and between Vdd and GND, etc., so see if I can find a short.

I’ll post some pics after that, but I don’t see any “blistered” chips, etc.

Hi,

I’ve been doing the above testing, and connections all appear to ohm out all right.

However, what I’m finding is that the Vdd pin of the AMC7135 chips, which are all tied together, are at 0V all the time, even when I have the board powered up from my bench supply. The Vdd pins appear to be coming from pin 6 of the MCU, so presumably that is how the MCU controls whether or not to drive current to the emitter, so it’s looking like the MCU is dead?

EDIT: Pics as requested:

Your AMC7135 chips in the bottom picture look either deep fried or grilled. :open_mouth:

That could be the problem. :slight_smile:

Power to the mcu goes through the reverse polarity diode next to led+(red wire). Check voltage there as well. If that’s ok then yes, the mcu is fried. Try a bit less flux or clean it off as it can block test leads from making good contact.

Rufus,

Did you mean the component I circled in red in the pic in the earlier post (I modified the pic)?

Hi,

I think it’s flux - I’ll clean it up and post a new pic after I check the voltage Rufus suggested.