LED Polarity - Interesting Find!

Great tip!  Thank you for sharing!!

May be a silly question but is the polarity critical when install replacement LED lights ???

I know Lionel peel and stick LED lights specify positive and negative

Just curious ? - what happens of polarity is switched ?

Thank you

Joe S

I've wired up literally a hundred LEDs, and never noticed the 'flat spot', I just key on the length of the lead.  Next time I'm working on them I'll look for that.  Thanks for the info.

@dorfj2 posted:

May be a silly question but is the polarity critical when install replacement LED lights ???

I know Lionel peel and stick LED lights specify positive and negative

Just curious ? - what happens of polarity is switched ?

Thank you

Joe S

Being a DIODE- Light Emitting Diode it doesn't pass current and thus does not light.

I've seen some with the flatspot on the wrong side, it happens.  I first noticed it when I laid out a board and just plugged it in based on the flat.  When it didn't work, I looked at the LED itself and could see that the positive side was to the flat.  Since then I've seen a couple different batches the same way.

I also ran across some red ones that had the long lead as negative, those threw me.  I've never seen that again.

Given the quantities these must be made in, not surprised at all. I'd go blind on that QC line......

In my limited experience, I have gone to using the inside of the led for the positive side. This comes from cutting the leads short for better fits in tight places, and sometimes grinding off the flange.

@John H posted:

In my limited experience, I have gone to using the inside of the led for the positive side. This comes from cutting the leads short for better fits in tight places, and sometimes grinding off the flange.

John, buy flangeless LED's, eliminates having to screw with the flange.   Most of the LED's I use nowadays are the flangeless type.

Thanks @gunrunnerjohn, I don't do it very often, but I'll get some. I do it mostly on the 3mm MTH headlights, so I can knock out the lenses and shove the led all the way out to the end of the socket. I like to see a spot on the wall when they round a curve. Never get any bad advice from you.

These are a perfect drop-in for the 3mm incandescent bulbs, much easier to deal with than hacking off the flanges.

I always forget which side is which and use my multimeter diode test setting to figure it out, plus to test and make sure the LED works before soldering it up.

I bought this for $2 on eBay, and I added a pair of clip leads to test if I didn't want to plug the LED in directly.

@gunrunnerjohn posted:

I bought this for $2 on eBay, and I added a pair of clip leads to test if I didn't want to plug the LED in directly.

You must have created a run on them, they're eight or nine bucks right now - who was selling this one at that price?

George

Inflation has pushed them to $3.15 on AliExpress.com, this one has free shipping.