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 Five out of Nine LEDs Work Swimmingly
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By: Anonymous: Satire () on Saturday, October 10 2009 @ 02:25 PM PDT (Read 10396 times)  
Anonymous: Satire

Hello! I purchased on of the Larson Kits, and just finished assembling it. Unfortunately, not all the LEDs are cooperating. I had just three working, then I checked all the connections and got two more glowing. Problem is, I've had no luck on the final four (D5 - D8).

I imagine this is user error somewhere, but I'm not sure where to look. I disconnected the final four resistors and resoldered them, but that didn't help. Any ideas?

I appreciate any help you can provide.





       
   
By: Windell (offline) on Saturday, October 10 2009 @ 03:33 PM PDT  
Windell

You can normally tell which solder joints are good by looking at them: they look like shiny wet pools of mercury. Bad solder joints are harder to spot. Check carefully-- with your eyes --to make sure that each of the solder joints *look* good, and make sure that there are no accidental "solder bridges" between things that shouldn't be connected. You need to check both the LEDs, resistors, and the pins of the microcontroller-- it only takes one flaky solder joint in that chain for an LED not to light.

Also (just have to ask) are you sure that you pointed all of the LEDs with the correct orientation when you inserted them?


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By: Anonymous: Jim Cook () on Saturday, October 10 2009 @ 05:22 PM PDT  
Anonymous: Jim Cook

Satire, I have seven out of nine 10mm L.E.D.s working properly. I'm sure it's my fault because after checking all the solder joints I found all of them to be good except the short lead of D0 and D2 appeared to be "cold soldered" (the ones that are not working). I tried to re-solder these two leads.

I'm a Mechanical Engineer and not an Electrical so I tried to devise a simple test.
I used another LED (test LED) and touched its leads to the back of each of the soldered leads of the kit LEDs. The test LED lit properly when touched to each active LED, but not on the two non-working LEDs. I de-soldered both no-working LEDs. Verified that both were properly connected and both worked when touching the working LEDs. No luck after re-soldering.

I'm worried that I damaged the lead in the circuit board during the initial soldering.

I'm open to any suggestions to help me find the damaged lead or connection.

I also purchased the 5mm LED kit, but I'm a little leery on building this kit before I find what I did wrong on the first.





       
   
By: Windell (offline) on Saturday, October 10 2009 @ 05:35 PM PDT  
Windell

>The test LED lit properly when touched to each active LED, but not on the two non-working LEDs. I de-soldered both no-working LEDs.

Desoldering parts when you probably don't need to is a *very* good way to end up with fewer working parts, so please exercise caution.

There's really not that much to go wrong in this kit-- either the bad solder joint is on the LED, on the resistor between that LED and the chip, or at the chip. Since you've verified that it wasn't the LED, you've narrowed it down, too, right?


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By: Anonymous: Jim Cook () on Sunday, October 11 2009 @ 11:09 AM PDT  
Anonymous: Jim Cook

You are correct when you say "There's really not that much to go wrong in this kit". I found that I used too much heat. I went ahead and hard wired one of the non-working LED's and bingo, it works. I'll do the same to the other.

Knowing this, I took more care with the 5mm kit and it worked the first time.

The 5mm seems to be brighter but both have a great fade in / fade out cycle, real smooth. I love it. Thank you very much,





       
   
By: Anonymous: Satire () on Sunday, October 11 2009 @ 01:28 PM PDT  
Anonymous: Satire

Thanks for the prompt response, Windell.

To the best of my ability I've checked all the connections, but I still can't get those last four to light. I think I managed to even burn out one of the LEDs along the way, but I imagine the other three would still be working. I imagine there's some negative effects to taking everything apart and resoldering it, but do you have any other suggestions before I take that step?

I don't know if there's some way to narrow down which could be the cause of the issue, or if there's a few connections I should check before doing it all again.

I think I've done enough repetition on this board that it's showing some strain, which may also be the cause. I'll be ordering another couple soon, because despite the problems I've been having it was a lot of fun.

I appreciate any help you can provide.





       
   
By: Windell (offline) on Sunday, October 11 2009 @ 01:44 PM PDT  
Windell

If you're fairly new at soldering, it's possible that you may have *cooked* the LED elements by heating them for too long.
They're pretty tough, but it can happen sometimes.

You can also do what Jim was doing. If you can identify one of the LEDs that's still good, you can use it to test each of the LED *locations* -- by touching it across where an LED goes. If the "location" is good, that means that the connections from the chip and resistor are all okay.


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By: Anonymous: Satire () on Sunday, October 11 2009 @ 01:46 PM PDT  
Anonymous: Satire

I'll give that a whirl and let you know how it goes!





       
   
By: Anonymous: Satire () on Monday, October 12 2009 @ 11:36 PM PDT  
Anonymous: Satire

Unfortunately, that didn't help. I put in an order for another kit (two, actually). I think I made a mess of this one. It must be something with the resistors, I think, but I'm just not sure. All the solder points look okay, but I've tried to correct things so many times that I think I stripped the contacts off the board, and I heard at least one LED pop. Trying to move working LEDs to the non-functioning parts didn't help.

On the upside, it was definitely still worth the money, even though it didn't result in a (fully) working unit. I learned a lot, and it was piles of fun.

Here's hoping the next set turns out better!

Thank you again for putting together such a fun kit.





       
   
By: Windell (offline) on Tuesday, October 13 2009 @ 12:12 PM PDT  
Windell

[...]and I heard at least one LED pop


Egads! Eek! Eek! Eek! Eek! Eek!

Perhaps obvious, but this really should not happen. Maybe I can give you a couple of pointers on soldering here. Big Grin

First, make sure that the tip of your iron is *shiny* like liquid mercury before you try to use it. If it isn't, swipe it quickly across a soaking wet sponge-- don't hold it there or it will just get cold. If it still isn't shiny, melt some solder onto the tip until it wets, and then swipe the tip across the wet sponge. If you can't get the tip shiny, you can't solder with it.

Second: make sure that you understand that the soldering iron is not a spoon. You cannot use it to carry solder to a joint that you want to make. You can only use it to melt solder *at* a joint that you want to make.

Third: Like many electronic components, solder contains magic smoke that causes it to work. When solder melts, it begins smoking. By the time that it stops smoking, it is *no longer solder.* If you should heat it long enough that it stops smoking, it's almost impossible to use it to make a good connection-- add fresh solder and try again.

Fourth: it's possible to cook components. When soldering small parts like these, most successful connections are made in the first one second of soldering. Place the solder at the intersection of the two things (resistor lead and PCB for example) that you're trying to join and press the shiny tip of your iron on that solder, at that intersection. The solder should melt instantly, and you should have a clean connection in about one second. (Count it out: one-thousand one.)
If you do not make a clean solder joint within two seconds of heating your parts, withdraw and move onto a different joint. Don't come back to that one for at least 30 s-- allow it to cool.

Finally, a good solder joint should look like a tear of shiny wet mercury, leading with a clean curve to all of the parts that it is supposed to connect. Your most important soldering tool is your eyeballs-- to inspect a solder joint to tell if it's good. If a solder joint is not good, you will need to apply fresh solder to fix it. The old solder, already at the joint, has already let out its magic smoke.



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By: Anonymous: Satire () on Tuesday, October 13 2009 @ 10:21 PM PDT  
Anonymous: Satire

Thanks for the tips... I haven't done soldering in many years, and I'm pretty rusty. It probably didn't help that I'm using a "Cold Heat" soldering iron that managed to make an LED pop when I touched its connection wrong. I'll try to borrow a normal soldering iron from a friend for the next round.

Assuming the next attempt (on a fresh kit) goes better, I'll try to double back and see if anything can be done with this board.

Thank you again for your help!





       
   
By: Windell (offline) on Tuesday, October 13 2009 @ 10:47 PM PDT  
Windell

I (and many others) would advise you to steer clear of the "cold heat" soldering irons. While I'd never advise anyone to use a $10 hardware store iron, they do tend to be better than *that.* Spending about $40 on a reasonably good iron (e.g., Weller WLC100, or a used Weller on eBay) will speed up your efforts by more than a factor of 10, and make success much, much more likely.


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By: Windell (offline) on Tuesday, October 13 2009 @ 11:03 PM PDT  
Windell

Addendum: You may want to look at these articles, and ratings and reviews of the coldheat.... Eek!

http://articles.marco.org/120
http://en.wikipedia.org/wiki/ColdHeat
http://www.eham.net/reviews/detail/4623


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By: q209 (offline) on Wednesday, October 14 2009 @ 04:37 PM PDT  
q209

I put together two kits in about an hour, and they worked wonderfully!

Of course, I learned soldering maybe forty years ago at the hands of teachers whose methods of criticism were wire dikes... Smile

I always use either: a variable heat soldering iron, or an iron with different wattage plug-ins. Why? So I can match the heat to the project.

I've cooked many a component. Even lifted a trace or two off a board... You want to be able to make a joint within three to five seconds max - or the heat gets too high, or the iron is too darn cold...

Wendell - is there a Maker class on soldering? It's a basic skill that's not taught much these days, and it's frustrating to learn the hard way! Maybe Lenore can hold some classes at a local pub... Smile Or folks can wander by my place late evenings out in the Central Valley...

Oh: the clear LED's don't seem to exhibit the "fading" effect as much. Which program variables would most affect that?

Thanks for a great kit!


Kevin


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By: Windell (offline) on Wednesday, October 14 2009 @ 07:45 PM PDT  
Windell

Wendell - is there a Maker class on soldering? It's a basic skill that's not taught much these days, and it's frustrating to learn the hard way! Maybe Lenore can hold some classes at a local pub... Or folks can wander by my place late evenings out in the Central Valley...


I have taught soldering classes before, and I'd like to do so again. Not sure what the right place to do it is, though. Certainly worth exploring.

Oh: the clear LED's don't seem to exhibit the "fading" effect as much. Which program variables would most affect that?


The exact same program is used on both versions. The trouble is that above a certain brightness your eyes can't tell apart variations, even when there's that factor of 60 between the brightest and dimmest values.... And those LEDs are painfully bright.


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