Dangerous Prototypes

My IR Toy just arrived and it's working great with the notable exception that the infrared LED isn't firing.  My questions are this:  what's the metal sleeve on the LED for?  I have a bunch of cheap infrared LEDs I got off eBay a long time ago... Any reason I can't swap one of those in? 

Hey Ytsirk - I'm sorry your IR toy isn't working. I'm not sure about the IR LED they used, I haven't seen one myself. You should be able to swap in any LED without a problem.

Out of curiosity, what is the value on resistor R5, right above the transistor?

No problem, it'll take a 5 min fix with a soldering iron.  Everything else works great! 
Label and multimeter put R5 at 100Ω.  PCB layout says it's supposed to be 1k doesn't it? 

For most emitters, yes, but with the seeeed emitter there was a problem passing self test and the resistor had to changed to 100ohms for the manufactured version. I'm not sure about the emitter they used or why it behaves differently (or why it was cheaper than a simple IR LED like I used in the prototype)....

I'm really glad you have the 100ohm resistor though, because it would have meant production error and that ruins my holiday weekend :)

So, I'm hoping this isn't going to upset your weekend.  Perhaps its an isolated incident, but in the process of swapping out the LED, I decided on a whim to throw it in backwards and sure enough it started firing.  So, it seems mine was installed backwards.  There is a tab on the metal sleeve around the LED that seemed to match up with the silkscreen on the PCB, but either it's on the wrong side of my LED or it's wrong on the silkscreen.

I'm sorry about the backwards LED. It's weird that it would pass the self-test at the factory if the LED was backwards. We'll have to wait to see if there are other reports of the same problem. I double checked the schematic and it is technically correct, but that doesn't mean the LEDs they used had the tab on the cathode instead of the anode.

It doesn't look good. I got the LED part number from Seeed, SFH480. Attached is the diagram from the datasheet. For this part the tab indicates the cathode, but for other parts it indicates the anode. This is opposite the silkscreen (not that the silk should be determining how anything is done in manufacturing, the schematic and board files should be used for that).

I'm awaiting confirmation from Seeed, and will post instructions on how to proceed shortly. I apologize for the inconvenience and for not getting this right.

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Posted: http://dangerousprototypes.com/2010/04/ ... -1-defect/ (http://dangerousprototypes.com/2010/04/05/usb-ir-toy-preorder-1-defect/)

Again, my sincerest apologies for the inconvenience caused, and thank you for locating the defect.