Problem building Blinky Grid SMT

[zucker]

My son and I purchased the Blinky Grid SMT kit at recent Maker Faire. Today my son soldered all the components to the board, but when we powered it up, it did not work. I would appreciate if you could help us debug the problem.

This is what we tried so far:

1. I inspected all the soldered connections. I think they look good. No obvious blobs of solder or unconnected wires. Please see the photo here https://plus.google.com/photos/111956285780546048166/albums/5745944859299091889 so you can see for yourself.

2. Checked the ‘G’ and ‘+’ holes at the top corners of the board with a Voltmeter. They measured 3.1v as expected.

3. Tried to measure the voltage to the IC by putting a voltmeter across pins 1 and 14. I thought this should also be 3.1v but it was not. It was .5v. I also tried measuring across pins 7 and 8. One time this measured 3.1v, but later I could not repeat this and it measured .1v.

My suspicion is that the IC is installed backwards. (since the voltage would be in the correct place if the IC is backwards--but I am confused why pins 7 and 8 do not always measure 3.1v). In my board, the dot is to the left. What should be the correct orientation?

4. At various times either after turning on the power or probing different pins with a volt meter some of the LEDs randomly light. I think this would be expected if the IC is installed backwards.

Please advise. What should I do to get my Blinky Grid to work?

Thanks.

[wayne]

Hi!

You appear to be correct on all counts. The board looks really good--tell your son he did an excellent job. The IC is also installed backwards. There's a "notch" on the IC silkscreen that normally indicates polarity--but most SOICs have dots, not notches, indicating pin 1, so this is less intuitive. We've marked this down as something to fix in the next board revision.

If you could, try flipping the chip around. My suggestion is to actually add more solder to both sides of the chip, until it's one big bridge. It should/may hold enough heat to let you wipe it off the surface. Otherwise, go to our contact us page (http://www.wayneandlayne.com/contact) and send us your mailing address, and we'll ship out a replacement red Blinky Grid SMT.

Hope this helps!

[zucker]

Hi Wayne,

Thanks for the info. As an aside, I am curious--why was I not able to consistently measure 3.1v across what I thought were pins 7 and 8 (actually pins 1 and 14) when the IC was installed backwards? Aren't these pins connected directly to power and ground?

Anyway, we were able to resolder the IC in the correct orientation, however, now several of the LEDs do not light. Here is a photo of the BlinkyGrid in a pattern with all LEDs set to light:https://plus.google.com/photos/111956285780546048166/albums/5746136760613016641

Do you think this is because the IC was damaged when we unsoldered and resoldered it?

I will take you up on your offer for a replacement kit. But still, it will be a good learning experience if we can get this one to work.

BTW, with regard to your comment here:
>>but most SOICs have dots, not notches, indicating pin 1, so this is less intuitive. We've marked this down as something to fix in the next board revision

Yes, this would be a big help to add to the directions. My son assembled the board without me and he did not understand what notch the directions were referring to (since as you say, the IC had a dot and not a notch)

Thanks,
Dan

[layne]

Hi Dan,

Nice work with the photos, that always really helps us figure out what's gone wrong. The LEDs that aren't lighting up in your photo are all associated with the LED4 signal line, which is connected to pin 6 on the chip, so you might look at that connection to make sure it's soldered down.

We received your contact form message and will get a replacement kit out in the mail today or tomorrow.

[rbreve]

Hi, I am having a similar problem, not all LEDs are lighting up, what could be the problem? Apart from that everything else seems to work fine, even programming.

Here is a photo

https://www.dropbox.com/s/8zrbdfj4yvi6n ... 9%20PM.jpg

[layne]

rbreve,

Sorry to hear that you're blinky is misbehaving. Have you tried entering in a pattern that turns on all the LEDs? Hopefully that's what you are showing in the image.

Based on that assumption (that the blinky is trying to light all the LEDs) it looks like a majority of the un-lit LEDs are connected to the signal LED2, so that might be a good place to start looking. The LED2 signal is connected to the lower-left pin on the chip (right above the "BL" in "Blinky Grid" written in white on the circuit board). Make sure that the chip's pin is firmly connected to the pad on the board.

The two un-lit LEDs on the rightmost column are not connected to the LED2 signal line, so you might just check those two LEDs themselves to make sure both sides of each LED are connected to their pads on the board, and that both LEDs are oriented correctly.

Good luck, let us know how it goes, and if you have any more questions!

[rbreve]

Thank you so much! it worked now, I just re-soldered the PIN2 and the LEDs and now they all light up, this is awesome