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 Debugging non-working strings
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By: Anonymous: Euan () on Sunday, December 16 2007 @ 04:18 PM PST (Read 3602 times)  
Anonymous: Euan

Howdy,

I finished asembling my first board yesterday (my first ever major soldering and I didn't blow any circuts, so I'm quite happy).

I've got three problems, and would like some advice on debugging;

- Firstly, the lights never truely shut off when at rest. One of each Positive/Negative string pair will remain with power (all be it dimmed) when all motion has stopped. This occurs on all four quadrants of the first panel. So a bit confused there. Normal with just one quadrant? A batch of bad resistors? (seems unlikely).

- Secondly four strings of lights don't work. I've checked the polarity (fine), and redone all the solders (also fine), although I can't remove enough of the solder to actually remove the LEDs and try again.

I tried using a multimeter to see where the power was going and if I could track it from there, but I'm just not experienced enough with electronics to work out what I'm looking for.

- Lastly, next to the two irregular capacitor placements (C103 and C104) I have two empty slots, and I can find no reference to them in the instructions. Not sure if I'm missing something, or they are for the soon to be released "walking table" expansion kit. Is Empty ok?

Help from fellow builders very greatly appreciated






       
   
By: Windell (offline) on Sunday, December 16 2007 @ 11:15 PM PST  
Windell

Hi Euan,
When everything works *perfectly,* all of the LEDs should settle down to very dim but not off after it settles down. If things work pretty well but not perfectly, half of the LEDs settle down to very dim and the other half settle down to fully off. When things settle down, if the positive string (for example) still pretty bright but the negative string is completely off, then you have a case of LED mismatch-- there's a not-so-good LED somewhere in that string. This is the "performance tuning" that's referred to in the instructions. If it's not severe or doesn't bug you, move on-- it won't hurt anything. If it's severe or bothers you, find the offending LED. When you excite that half-quadrant and watch it cycling, notice that it swings between one of two groups of five LEDs being on at a time. As it's starting to settle down, you might notice that it starts to be not five and five, but five and *four* LEDs in the other set, indicating that there's a weak one that's not turning on at the same time as the others: replace it.

For the "four strings of lights" that aren't working, I'm not sure that I can help much without knowing exactly which LED sets you mean. So, I'll be general: problems like this can be caused by (1) an LED facing the wrong way, (2), a bad or missing solder joint on the LED chain OR elsewhere in the components for that quadrant, (3) wrong number of jumpers in the chain of LEDs (should be exactly one in each half quadrant's positive section and one in the negative section), (4) wrong-value resistor installed as a component in that quadrant. As you see, it's still somewhat nebulous. Since the problem occurs in more than one place, it's probably not due to a bad component. Generally speaking, problems like this can be solved without the multimeter by walking through that list and checking.

The two empty slots next to C103 and C104 are designated as C105 and C106. As it says on the bill of materials, these are optional locations for extra capacitors and should be left empty.


Windell H. Oskay
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By: Anonymous: Euan () on Monday, December 17 2007 @ 02:19 AM PST  
Anonymous: Euan

When things settle down, if the positive string (for example) still pretty bright but the negative string is completely off, then you have a case of LED mismatch-- there's a not-so-good LED somewhere in that string



Yup - that would be it. I re-soldered just about the entire board (although I can't get enough solder out to remove anything cleanly which is quite frustrating) looking for lose connections and solved the half on strongly problem per another of your posts. Now it's just down to imperfect LEDs. I'll do the other panels and see if I want to come back and fix it on the first.


So, I'll be general: problems like this can be caused by (1) an LED facing the wrong way, (2), a bad or missing solder joint on the LED chain OR elsewhere in the components for that quadrant, (3) wrong number of jumpers in the chain of LEDs (should be exactly one in each half quadrant's positive section and one in the negative section), (4) wrong-value resistor installed as a component in that quadrant.



I've done 1, I think 2 (but will try again - I resolved one string this way). 3 is OK. and 4 I'll need to check.

I think the bad solder is going to be the main answer. I was trying to debug them a little and noticed that when I pushed on the second pin on the circuit (on the right) in the quadrant with some failed lights and they lit up, so I'm guessing that connection is bad (interrupted by baby before I could finish looking at it).

I wanted to say it is a fantastic kit, BTW.

I showed someone at work today as we plan out a booth for a trade fair, and they wanted to get a long series of panels down the side of the booth to capture peoples attention as they walk past.





       
   
By: Windell (offline) on Monday, December 17 2007 @ 02:28 AM PST  
Windell

I've done 1, I think 2 (but will try again - I resolved one string this way). 3 is OK. and 4 I'll need to check.


Sounds like you've got the knack of solving these little bugs-- once you've fixed the first of them, you're on your way just fine.
If you do get stuck again, I'll do my best to point you in the right direction.

I wanted to say it is a fantastic kit, BTW.


Thanks! Big Grin


Windell H. Oskay
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