red LEDs from SmashTV

Parts Questions
1

Smash

I got 100 LEDs from you and I’ve been using them on my prototype setup.

I’m a newbie when it comes to electronics but I’ve not read anything otherwise about LEDs.

My LEDs light up once or twice and that’s about it.

When I initially got the package, I hooked on of them to a 5V source and it lit up a couple times then stopped. I figured I might have blown it for wiring it directly like that.

Now I have 8 hooked up to my DOUT and by using the Debug Fuction features in MIOS Studio, I got the lights to light up 2 times and no more.

Is there something obvious I need to be aware of?

2

Well, Leds cannot be supplied with direct voltages, you need to limit currents with resistors (Dout provide 220Ohm resistors for each line).

My leds work ok and I bought them from Smash

3

I found this image and I used it as a reference because I couldn’t find this info here.

http://web.mit.edu/~awozniak/Public/6.121/LED.html

The image shows the short lead as being the cathode lead. And by looking at the LED closely, you can see the crescent shape.

On the LEDs I got from Smash, the short lead isn’t on the crescent side. It’s just the reverse.

So, now I’m confused. I’ve probably blown those 8 LEDs.

When I wire them up, I went solely by the length of the lead to determine which one would be connect to a DOUT pin and which was ground.

http://www.ucapps.de/mbhp/mbhp_doutx4_32leds.pdf

The DOUT schematic shows the ANODE lead connects to the DOUT pins. The external image suggests the anode would be on the long lead.

I’m guessing that image is wrong, right? The long lead should be the cathode, and the cathode lead should be connected to VS ground.

Oy vey!

4

The image is right!

Cathode = short pin (Easy to remember in German: K athode = K urz (short))

Anode = long pin

Raphael

5

… most of todays multimeters have a diode test function (beep) if you’re not shure.

Greets, Roger

6

I’m so confused on this… it ain’t funny.

The problem is, the diagrams on this site, isn’t including what wire from a LED is what. I have a boat-load of LEDs that have short and long pins… I’m also fixated on the shape inside the red diffuser; on top of all that… my DOUT isn’t making anything blink reliably.

So, should I ignore the shape inside the red area and just concentrate on the pin lengths? Short pin (cathode) goes to VS ground; long pin (anode) goes to the DOUT pin.

Oy freekin’ Vey!

7

Just be glad you’re not dealing with “used” ones, where the legs are already clipped :wink:

I’ve gone by the metal pieces inside as well, but I’m not sure if that’s always the same. Remember there’s also a flat side on some for the cathode.

Here’s another link:

http://www.kpsec.freeuk.com/components/led.htm

8

The interior of my  LEDs look exactly like this image, except the length of the pins is reversed. My long lead runs into the triangle shap inside the LED. My short lead runs into the straight and narrow shape inside the LED.

Here is the image from Smash’s site. These are the LEDs I bought.

So, before I solder anything else and potentially burn up more LEDs, can someone please tell me which wire (according to Smash’s image of the LED, should I connect to VS ground and which wire connects to the DOUT pins?

Thanks

9

Screaming

" most of todays multimeters have a diode test function (beep) if you’re not shure."

Bingo! Newbie learns something!

I never cared to investigate the feature.

Thanks Screaming Rabbit.

10

Thanks guys for all the answers, we need to roll all this into a page on the wiki… :slight_smile:

I’ll add:

Don’t ever go by the shape of the pins inside the substrate, as this varies greatly from one factory to another.  It’s all about the direction the die is placed, and assuming the operator was not asleep loading the die tube it will always follow the lead length and flat side of the package.

Unlike high brightness leds, these won’t supernova (go super bright) when you give them too much current, they die a relatively quick and quiet death.  Unless you wire them to mains voltage, then you are in for a show that includes sparks and smoke…These could make a cheaper alternative to the squibs pyrotechnicians use to electrically ignite pyro devices…  ;D  --do not try this, it’s dangerous and will stink up your house if it does not burn it down–

Best!

Smash

11

Hey Smash teach me those tricks and let’s go for a tour around the world! I order 100000000000000 leds (don’t take me seriously :D)