Surface mount soldering help

[skyler...@gmail.com]

Hi Guys...

Asking for some help here. I recently bought four LED display modules that are driven from an arduino.

Over the last few weeks, I have put the modules together, but have never had any luck with getting them to work. Last Thursday, with the help of Lauren, we discovered that I was getting alot of line noise over the input/output pins.

I can only think this is due to my soldering technique. While I have had some experience, I'm no getting the results I'm after. Looking for someone who is far more experienced that I to look over my shoulder as I build the last module to see if I can get it to work. 

Love any input anyone has to get these made and working. If I can salvage the other modules, that would be great, but right now I would love to get one to work.

-Gil

[Zac Watts]

Do you have more info on the modules and how they are meant to be wired up? I'm doubting that poor soldering is resulting in noise... maybe you have lines that are floating and need a pull-up/down resistor...?

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[Gil Poznanski]

Sure...

Here is the data sheet link to the kit : Data Download

- Gil

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[Zac Watts]

For those playing along at home it's a 24 pin soic chip. I'm going with its a soldering issue now.

Id use some solder wick to try and remove excess solder for starters and see if that works. Other wise remove the chip, clean the board and pads of all the solder you can, and take another crack at it. Maybe try the solder paste in the fridge.

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[Luke Weston]

I'd say it's unlikely that there is "noisy" soldering... the joints are either soldered or they're not. Intermittent or "dry" solder joints are pretty rare, especially on newly soldered joints, and especially on SMD components.
I'd say the most likely soldering issue for a beginner working with small SMD components would be shorts between adjacent pins, and too much solder... open circuit joints are really quite unlikely, you need very little solder to have a reliable, intact connection and it's much easier to put too much solder on than too little.

I will have a look at it for you next time I'm there, if you're there too.

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[michael borthwick]

Hi Gil,

From what I saw of the symptoms on Thursday they are not consistent with 'line noise', whatever that is. If that is 50Hz mains hum you could eliminate it by powering the setup off batteries or any decent regulated power supply. If it is noise in the SPI interface lines then I would expect erratic behaviour.

1. What exactly are the symptoms ? - AFAIK all three modules are completely non-functional - they never do anything - you've never had a single LED light up - is that correct ? That's important.

2. I think noise is a red herring - if it isn't it is not going to be so as a result of your soldering.

3. I would not try and remove a 24 pin surface mount chip unless you have soldered it on the wrong way around ie Pin 1 is where Pin 24 should be. It takes experience, confidence and the right tools and materials to desolder a part with so many pins. It's not 'hard hard' but you have a good chance of overheating the chip, lifting traces on the PCB and generally getting frustrated and there isn't going to a little man trapped under there shorting power and ground as a way to get attention.

SOIC package is as agricultural as surface mount gets. If your eyesight is OK you should be able to see any solder bridges, even slight magnification will indicate whether you have bridged any pins and on a board with a solder mask it is pretty hard to do that.

Assumptions:

1.  You haven't been sold 4 dud module

2. You've done obvious checks and no component is getting hot and there is not a short circuit between power and ground 

After that I see the troubleshooting breaking down into three high level areas A, B and C below:

A Error in assembly

A.1) 24 pin SOIC is soldered around the wrong way.

A.2) Capacitor C2 (polarised) is soldered around the wrong way

A.3) Parts mis-identified and soldered in wrong place

B. Module OK but error in hookup

B.1). You have incorrectly wired the SPI lines between the Arduino and the module - do you have another SPI part to verify hookup

B2). Your funky hookup wires are faulty - test their continuity with a multimeter

B3) Power and ground to module reversed.

C Module OK and correctly wired but error in software or faulty Arduino hardware

C1. Arduino is blown-up (can you load a sketch? flash an onboard LED?)

C2 The sketch is wrong as published or your changes to it for your Arduino model or specific connection are wrong. SPI initialisation wrong, wrong SPI port being used on multi-port device. Something broken in your version of Arduino IDE or library. Have you got any test equipment at all (even a LED) that could verify activity on the SPI lines at the appropriate time. ie write a new sketch or add some delays to existing sketch so you create burst of SPI activity separated by gaps of a few seconds that you can easily pick up with an LED, multimeter or some 'known good' chip or module that speaks SPI.

You've almost certainly fallen into what Robert Pirsig described in Zen and Art of Motorcycle Maintenance as a 'gumption trap'. These can be overcome by taking a break from the project over a cup of tea, or sleeping on it - which will give your subconscious time to work on it.

Cheers,

Mike

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[Trystan -Crenn- Jones]

If you're there tomorrow, I can take a look at it if you want.

-Crenn

On Tue, Apr 22, 2014 at 10:37 PM, Luke Weston <reindeer...@gmail.com> wrote:

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[Luke Weston]

Looking at the schematic and documentation, here a few things I would consider. Note that I haven't looked at your actual hardware:

- Has the LED module been mounted upside down? (Call it an educated guess, that's the first thing I would try.)

- Has the MAX7219 been mounted upside down?
- Has the MAX7219 been damaged through the application of an excessively high, or polarity-reversed, supply voltage? (Personally, I'd go for hot air as the easiest way to desolder it, if necessary.)
- Are the Vcc and ground pins connected to appropriate power supply pins on the Arduino? (5V will be perfect in this case.)
- Are the SPI signals (MISO, MOSI, SCK and CS) connected to the right pins on the Arduino? It can be easy to get them mixed up, I've done it before.
- Does the pin used for CS on your hardware match the pin defined for CS in your software?

- Do you know that the software you're using works?
Try starting from scratch with some really simple example code to talk to the MAX7219.
Read the following, and try the simple example code provided:
http://tronixstuff.com/2013/10/11/tutorial-arduino-max7219-led-display-driver-ic/

http://tronixstuff.com/2013/08/25/kit-review-friedcircuits-led-matrix-link/

Exactly what sort of microcontroller are you using to talk to the MAX7219 board? An Arduino?

A SOIC chip is actually pretty "coarse" as far as surface mount is concerned, solder bridges between pins should be quite unlikely and unambiguously visible if they are present. You should be able to rework each pin with a soldering iron, without tools like hot air.

Here's a MAX7219-based display I built about 5 years ago, in case you're interested. The system uses essentially no components other than the LED displays, MAX7219 and Arduino - just one 0.1uF cap across the power pins on the MAX7219, and the current-set resistor.

https://twitter.com/lukeweston/status/458607454050205696/photo/1

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[tubular]

Hi Gil,

When I looked it briefly last Thursday, I found the "ground" wire from the input connector, didn't connector to the ground of the output connector.  There wasn't multimeter continuity, despite everything looking OK (including your soldering)  to the casual glance.  It also explains why you were seeing a 'clock' signal appearing on one of the data pins - parasitic power being delivered between Vdd/Vcc to whatever data pin was pulled low at the time

I don't quite know what was going on - faulty vias in the pcb?  Hairline cracks?  

Anyway I would use a multimeter to check point to point continuity of the signals going to/from that IC, against a circuit diagram.  Its unusual to have to look for this kind of fault, but given we've seen one case it'd be well worth double checking the other signal traces too. 

regards

Lachlan 

[Lauren Shearer]

Hi all,

I put my clumsy mits in last week as well, so thought I'd pipe up things we'd also done

SOIC package is as agricultural as surface mount gets. If your eyesight is OK you should be able to see any solder bridges, even slight magnification will indicate whether you have bridged any pins and on a board with a solder mask it is pretty hard to do that.

I couldn't see any under a magnifying lens

 

B.1). You have incorrectly wired the SPI lines between the Arduino and the module - do you have another SPI part to verify hookup

Not another SPI device, but we changed which arduino pin was which about a dozen lines to make sure

We also set data, clock and chip select to pin 13 at times and saw appropriate LED flash

We also check that the signal got to the MAX board end of the wires.

 

B2). Your funky hookup wires are faulty - test their continuity with a multimeter

Above

 

B3) Power and ground to module reversed.

If so, error on silkscreen 

 

C1. Arduino is blown-up (can you load a sketch? flash an onboard LED?)

Yes, several times, and MISO, CLK and CS seen on the LED

 

C2 The sketch is wrong as published or your changes to it for your Arduino model or specific connection are wrong. SPI initialisation wrong, wrong SPI port being used on multi-port device. Something broken in your version of Arduino IDE or library. Have you got any test equipment at all (even a LED) that could verify activity on the SPI lines at the appropriate time. ie write a new sketch or add some delays to existing sketch so you create burst of SPI activity separated by gaps of a few seconds that you can easily pick up with an LED, multimeter or some 'known good' chip or module that speaks SPI.

The sketch was straight from the manual. We did not specifically look at addressing beyond the first chip in the series being the only chip

Activity confirmed on LED and multimeter

 

I'd say the most likely soldering issue for a beginner working with small SMD components would be shorts between adjacent pins, and too much solder... open circuit joints are really quite unlikely, you need very little solder to have a reliable, intact connection and it's much easier to put too much solder on than too little.

I did some hot air "reworking" on all the components (Shielding the MAX chip with foil and got the solder to wet)*, re-soldered the 0.1" headers, and a general clean-up.

I verified that LEDs could be lit with direct power at low voltage. They can.

Turned the LED module around 180 degrees. No change.

I verified that the sketch was generating signal on the appropriate lines (LED and Oscilloscope)

I rote a customized sketch to send the "DEBUG" command to the MAX with no success.*

I tried power from the arduino (Computer -> USB -> arduino  -> 5v regulator -> pin -> MAX board) and power independant of the arduino (Benchtop supply)

I'm fairly sure we put in some filter capacitors at one point to reduce the line noise

I tried bypassing the library to send commands directly to the module (using the function from the library)*

* indicates stuff I understand but am not proficient in

We found one thing that was interesting and beyond my understanding, possibly related to on-chip issues. My memory of the specifics is now vauge.

When sending a sketch, if all pins (+5v, GND, MISO, CLK, CS) were connected, the signal on all of MISO, CLK and CS and GND seemed to be the same,  mostly AC noise at (I think) 2.6v or so. This was with the LED indicating signal was being sent.

As I indicated, the exact finding at the end I can't remember but there was some combination of AC noise and bleeding signal across pins - after checking that 5v and GND were isolated from each other and the signal pins were isolated from each other.

I would say, the PCB board design seems bizarre with vias used when not obviously needed and unbalanced +5v / GND traces

Cheers.

 

I will have a look at it for you next time I'm there, if you're there too.

On Tue, Apr 22, 2014 at 10:10 PM, Zac Watts <zwa...@gmail.com> wrote:

For those playing along at home it's a 24 pin soic chip. I'm going with its a soldering issue now.

Id use some solder wick to try and remove excess solder for starters and see if that works. Other wise remove the chip, clean the board and pads of all the solder you can, and take another crack at it. Maybe try the solder paste in the fridge.

On Tue, Apr 22, 2014 at 9:32 PM, Gil Poznanski <skyler...@gmail.com> wrote:

Sure...

Here is the data sheet link to the kit : Data Download

- Gil

On 22 Apr 2014, at 8:57 pm, Zac Watts <zwa...@gmail.com> wrote:

Do you have more info on the modules and how they are meant to be wired up? I'm doubting that poor soldering is resulting in noise... maybe you have lines that are floating and need a pull-up/down resistor...?

On Tue, Apr 22, 2014 at 8:42 PM, <skyler...@gmail.com> wrote:

Hi Guys...

Asking for some help here. I recently bought four LED display modules that are driven from an arduino.

Over the last few weeks, I have put the modules together, but have never had any luck with getting them to work. Last Thursday, with the help of Lauren, we discovered that I was getting alot of line noise over the input/output pins.

I can only think this is due to my soldering technique. While I have had some experience, I'm no getting the results I'm after. Looking for someone who is far more experienced that I to look over my shoulder as I build the last module to see if I can get it to work. 

Love any input anyone has to get these made and working. If I can salvage the other modules, that would be great, but right now I would love to get one to work.

-Gil

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[skyler...@gmail.com]

Hey Guys...

Thank you all for your your replies. 

A quick update on the LED modules.

Last night I went in and attacked the modules again. With Lukes help, we got one of the modules to run the test sketch. As Gavin kept repeating throughout the evening, it was Awwwwsome! :)

Luke also gave me some SMD tips, and I went to solder my last kit. That one fired up first time around.

Spent the rest of the night trying to troubleshoot the other two modules. The module Lauren help me troubleshoot never fired up. The other module had a resistor issue and after fixing the solder on it, the first row fired up, but nothing more.

I believe that this issue was more to do with my solder skills and maybe a faulty chip (but I doubt it what that!) I ordered a few more modules and will continue practising my SMD work. 

Thanks for all your help. 

-Gil

[Trystan -Crenn- Jones]

Glad to hear that my tips were useful last night and the last one work worked off the bat. I might make a brief appearance at the space on Saturday after my 'shift' at Masters' BBQ, so if you're there I might be able to help you get the others working.

I think carefully using the hot air reflow station to get those other chips centred on the pads may help, and giving them a light touch of solder on some of the pins will minimal solder.

-Not Luke

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[Gil Poznanski]

Sorry Trystan....

As many members of the space can tell you, I have a very bad memory for names, please dont take it personally, and I stand corrected!

-Not Bill...

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[Trystan -Crenn- Jones]

No problems and was more bemused than anything; know the feeling with trying to remember names. Usually have to talk to people on several occasions before I remember their names. I'll also try to wear a name badge next time I'm at the space.

-I can't believe I'm not butter

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