Blinky POV SMT troubleshooting


#1

I just soldered a Blinky POV SMT. I think that I messed it up. When I turn on the the switch with the push button pressed, I see LED D1 blinking and LEDs D3, D4, D5, D7, and D8 are very dully lit up. LEDs and 7 are completely dark. Then I press the push button again for starting the programming, LED D1 goes completely dark and the LEDs D3, D4, D5, D7, and D8 remain dully lit. I have a digital multimeter. Can someone suggest what to test to troubleshoot this setup? Thank you!


#2

Hi Praveen, sorry to hear that your kit isn’t working correctly, I’m sure we’ll be able to figure out what’s wrong.

Does the kit work ok in normal (non-programming) mode?

Just to confirm, the chip is installed correctly, right? The divot in the chip’s top surface should be in the upper-right corner when viewing the kit right-side-up (as in the image below). The writing on the chip’s top surface will be upside-down when viewing the kit right-side-up (as in the image below).

Can you double-check that all the LEDs are installed correctly? Polarity on SMT LEDs can be a little tricky (scroll down to step 6 on this page to see the polarity indicators http://www.wayneandlayne.com/projects/blinky/build/smt/)

You should have the green dots on each LED towards the bottom of the PCB like in this photo:

Could you take a high-resolution but still focused photo of both sides of the kit? I think you should be allowed to upload images to this forum, but let me know if you can’t.


#3

Hi Matt, Thanks for offering help. I’m not able to upload pictures. It says that new users can’t upload. Once I have upload privilege, I’ll upload the picture and explain what I found so far.


#4

Hey there, I believe I have upgraded your user trust to enable you to upload images. Let me know if it still doesn’t allow image uploads, we’re still learning the new Discourse system.


#5

Thanks Matt. Here is the picture of my board.


#6

Hi Praveen,

From a first glance, most things look good to me. The chip is installed in the correct orientation, I don’t see any obvious solder bridges, and most of the solder joints look nice good. It looks like the only thing obviously wrong is that D6 is upside-down (and the green dot should be towards the bottom of the board) but that should only prevent D6 from ever lighting up. You might try using your soldering iron to re-melt some of the more ball-like connections to the LEDs, especially LED 2.

  1. Does the kit work normally when you don’t hold down the button while turning on the power?
  2. What color LEDs do you have?

#7

Hi Matt,

Thank you very much for helping to troubleshoot. I never noticed that D6 was incorrectly soldered. You were talking about the green dot. But, it never revealed itself until I took the picture. I didn’t use any magnifier to inspect the work. Sorry about that.

I used a soldering wick to suck off all the solder. But, it was impossible to remove the LED even after there was no visible solder left. I used Eutectic solder, so I guess that it is either solid or liquid at a given point. Hence the removal was difficult. I then cranked up the solder temperature to 730º C from 630º C. But, I managed the LED in the process. The LED came off, but it is not usable anymore.

I got red LEDs with my kit. Is there a part number or something so that I can find in my nearby Fry’s?

After removing the LED, I also cleaned up the board with isopropyl alcohol to remove all the flux mess that was left around. After that, I was able to successfully download text on the board and it works fine. Of course, D6 is missing :slight_smile: I’m not sure if removing D6 fixed the issue, or cleaning up the board with isopropyl alcohol fixed it. I doubt if the latter really affect anything at all. Anyway, it works now!

Thank you very much for the help. I feel stupid for reversing the polarity on D6. I was really careful while soldering it. But, still I ended up messing it up.

I bought this kit to learn to solder SMT components, especially of size 1206. I’m building my own keyboard that will have 78 SMT diodes. I hope that with this lesson, I’ll be more careful with the keyboard and not mess up the diode polarity.

Here is the picture of the product, after D6 was removed, and cleaned up.


#8

Hey there,

No worries, these are small parts, inspection is difficult. Much more fun to just try it out first :smile:

I’m very glad you got the LED off, and that the programming is working correctly now, congratulations! The cleaned-up board looks beautiful, too.

That still leaves the issue of missing D6. Any 1206 LED should work just fine. An 0805 might even work too, they are pretty close in size. Does Fry’s stock SMT parts? If so, that might be a good choice. Otherwise, we can definitely send you a couple more LEDs, just fill out the contact form with your address and we’ll take care of it this weekend.

This is the exact LED we are using for the Blinky SMT kits: Kingbright APTL3216SURCK (link is to Mouser). They are $0.19 each in quantity 1, but between the minimum order amount and shipping, it will likely set you back much more.