LED Board resistance question

[oldcqr]

Please be gentle and don't laugh too hard. I'm an electronics newb.

I'm in the process of building my LED board. I just measured, and the method I am using to connect to all the LEDs is going to add between 2.0 and 2.6 ohms of resistance. I realize there is resistance in all wires, and that these numbers are close to 0.... I just want to make sure that I am going to be within spec when I'm finished.

[djulien]

I just measured, and the method I am using to connect to all the LEDs is going to add between 2.0 and 2.6 ohms of resistance

How did you measure this?

don

[oldcqr]

I picked an intersection, jumped it with a small piece of wire (as if an LED with 0 resistance were installed), then measured the resistance by touching one probe to the row and the other to the column.

[Ronp]

I have built the ledtriks pannels using over 8 foot of wire to conect 16 led and it still worked.I dont think you will have a problem.

http://media.putfile.com/multitriks they may be small but whe main wiring harness is over 8 ft

[MikeUK]

LEDs are tricky... Until you exceed the minimum forward voltage for them to conduct, you cannot measure anything, especially resistance... So it all depends on your DMM battery, if you change it for a fresh one, then you will get a completely different reading across LEDs in series/parallel. Don't worry, it will be OK in the end.

[oldcqr]

Thanks all!

I'm now in the process of building the actual sign board for my Led Triks project. If you have a hanker'n to watch someone test and solder nearly 800 LEDs, now is the time to tune in!


Land O Lights live video feed (http://www.landolights.com/main/component/option,com_wrapper/Itemid,40/)

[Ronp]

Are you having fun yet .lol
looks nice so far I usualy put in 48 across then solder them .

[oldcqr]

Are you having fun yet .lol
looks nice so far I usualy put in 48 across then solder them .

Thanks.. The copper foil tape is working well, as long as you get the timing right. If you hold the iron too long on the joint, the solder runs clear across it and there's not enough left to make a good connection with the LED.

[Ronp]

Funny watching you make me want to go start another one
I also like to test with a 3v battery some leds may light dim so I eliminate them imediately

[oldcqr]

Funny watching you make me want to go start another one
I also like to test with a 3v battery some leds may light dim so I eliminate them imediately

I had been testing them with the LED tester from BestHongKong, then I noticed that my meter was lighting them when I was testing for continuity/correct installation.

So now, they get tested after they have been installed. Saves me a few steps and I should be able to see dim ones from the back side.

[oldcqr]

I finished 256 LEDs yesterday, and I'm trying to get the other 512 installed today. The link is above if you want to watch (and listen to some 80's music).

Ustream (http://ustream.tv (http://ustream.tv/)) also has a chat application if you want to ask a question. You'll have to search for my channel (landolights), and you may need to sign up for a free account.

[51fordf2]

Lunch? LUNCH??? What is "lunch" when you have so many LED's to install????

http://www.crbest.com/lmao.gif

(for those who haven't a clue, just looked at the live feed, and there's a big sign, that says "lunch".)

I'm anxious to see - I should be getting my boards before too awful long (thanks, Frank!), and I already have the led's.

I rather wish I had bought the Best tester, when I ordered LED's once before, but didn't. thinking of building my own, using a header, and resistors...not much more to it, really. I don't mind the $10 price, just the added $10 shipping!

Anxiously waiting...

R

[oldcqr]

I won't tell you about almost missing an appointment today due to my LED installation and a clock that decided to stop ;)

On a serious note... I purchased the LED tester from BestHongKong, and only used it for about 48 LEDS. I quickly discovered that while testing my soldering job with my ohmmeter, the 3 volts it was putting out was enough to light the LED.

To save time, I install all the LED's, then use the meter to ensure they light (thus also testing my joint). The 'real' LED tester is just sitting there now.

If you really want one, I'll sell you mine for $12 shipped ($10 + $2). PM me if interested.

[oldcqr]

Last chance!

I have 3 more columns to solder in. Then, I'll be wiring up the board and trying to figure out how to do some strain relief.

Later this afternoon, I'll be firing it up for the first time and hoping the blue-smoke genie doesn't escape!

Links posted previously....

[51fordf2]

Hmmmm....that board looks 1/32" off....from here, anyway...

:)

R

[Ronp]

you may want to read this too mike
http://doityourselfchristmas.com/forums/showthread.php?t=6383
and this post 16-17
http://doityourselfchristmas.com/forums/showthread.php?t=4126&page=2

[oldcqr]

you may want to read this too mike
http://doityourselfchristmas.com/forums/showthread.php?t=6383
and this post 16-17
http://doityourselfchristmas.com/forums/showthread.php?t=4126&page=2

Those were a couple of good reads.

I really think I have cabling probs, especially for columns 32-48. I have the dim/shimmer problem in other areas, but those 16 are the worst.

RS is showing the 1N4001 Diodes in stock, I may jump down there and pick one up. The supply I am using is old old old so I may swap it out as well. I never tested the voltage coming out of it -- it may be a bit out of spec.

[Ronp]

32-48 on the front is 1-16 on the back so im thinking davids fix may be it

[oldcqr]

32-48 on the front is 1-16 on the back so im thinking davids fix may be it

You were absolutely, 100% correct. Adding the diode immediately fixed 90% of the problems.

I can now see I have 2 columns shorted (bad cable), and I do occasionally see some LEDs light dimly that shouldn't. Again, my crimping skills SUCK, so I am blaming it on my wiring.

I'm going to go get my serial cable from the house. Can you point me toward that test program you mentioned (or is it only for parallell)?

I suppose I should DL Vixen as well :p

[oldcqr]

Woo Hoo!!!! My Triks/Triks C is now fully functioning, with NO problems.

All it took was a bit of reading. Ron P was right on the money when it came to not one of my problems (the flicker), but the other as well (a column stuck on dimly).


I was out in the workshop most of the afternoon working on the thing, mostly trying to get that one column to go out. I did a ton of stuff:

I first suspected a bad cable or crimp. I replaced the cable with a known good factory made one. No help

If I disconnect the Triks C, most of the LEDs in that column will go out (but I do get the occasional random LED turned on).

I changed the cable between the Triks and the Triks C. No improvement.

I ran a ground from the Power Supply to the computer driving the Triks. No improvement.

If I run a #CLS LTC command, the column stays lit

If I run a #BLK LTC command, the column goes out.

I ran separate power lines from the PS to the Triks and Triks C. No help.

I placed both the Triks and the Triks C after the diode. No change.

I swapped around all the Allegro chips. The column stayed in the same place (it didn't move with the chip).

Disconnecting the Serial cable doesn't change anything.

I was just about ready to pack it in, when I went back and read the other post Ron pointed out. Sure enough, there was my problem (right down to including the out led):

TimW posted:

"4) Bad Leds in a column
Sometimes people see a column of LEDs dimly lit all the time (usually with one led out). Replacing the led that is out -or working through the column replacing led until you find the bad one seems to fix this."

5 minutes later (4:30 for the iron to heat, 30 seconds to replace the 'bad' LED), and the thing works like a CHAMP!

WOO HOO!

[51fordf2]

Aw, shucks, was hopin' to see it - been in and out on your cam this afternoon (between etching a few pcb's), and saw you hammerin' and stammerin'...now off the air...

Great, glad you got it figured out! It was a little bit hard to see the lights, but it was obvious some were lighting now and then, on the Mikey-Cam. When you get it programmed, are we going to get to see it??

There's hope for me, yet!!

:)

R

[Ronp]

cool.. congrads after all the hard work nice that things worked out .

[oldcqr]

Last day!

And if you thought the last 3 were boring, wait until you see todays show. For the next hour or 2, I'll be straightening the LEDS. After that, I'll be running some more tests...

Speaking of LEDs... I'm already thinking about building another board for the other side of the display. If there is one thing I don't like about this project, it's the viewing angle of the LEDs. I'd really prefer a solid color LED vs the clear, so the viewing angle is infinite. I'm also leaning toward a green one vs a red one (chistmasy, eh?). Any suggestions on where I can find what I want at a reasonable price?

Something like this appears to be what I want... But is it REALLY what I want? Would I be happy? :confused: http://www.allelectronics.com/make-a-store/item/LED-2/GREEN-5MM-T1-3/4-LED/-/1.html

[51fordf2]

Mike,

That LED should be fine. Th only thing I have noticed, is with diffused, and looking at all the boards I see everywhere I go (thanks, DIYC!!), is that they seem to "blur" a bit, kind of fuzzy compared to the clear ones. But you are right, they are visible at a greater angle, it seems. I never thought about the angle, just the fuzziness, when I was looking. I bought clear blues, hope I'm happy with them, although where I plan to put mine, it will be a straight-shot only viewing ability. I took that into account when I went with blue. I've only seen one blue sign, and it seemed a little "subdued" in comparison with the red's, but it WAS nice!

I even thought about alternating rows, between red and green, but that would be a lot of effort, if it looked like crap! But, I think it would indeed look christmasy, and look ok. I have my buffer board leds alternating red and green, and it looks neat, as it flashes the leds', especially in a chase sequence. Guess I could lay it out in Vixen, alternating, and see what it looks like...

Great work (and music too!)...love it!!

R

[oldcqr]

Cool. I'll have to order em and see what they look like.

FYI: The music is 'Retro Active' from 'Music Choice'. Most cable co's use them for their music channels (DirecTV used to until they switched to XM). You may be able to stream them from musicchoice.com (but it may be a 'subscribers only'. Give it a try).

Grr... Broke a wire.. Boo!

[Ronp]

from 15 plus feet away the veiwing angle looks fine. you only notice it up close.