Pre-wired SMD LED’s

[wvgca]

to achieve a more 'old time' yellow glow [read less blue] i simply used a coat of Tamiya translucent orange on the SMD after completing / installing ... worked very well, seldom was a second coating needed, even on steamers  ..i seldom used daylight colours, instead using plain ole blueish leds with a coat of orange, the ones used for ditch lights were squared off in appearance[like in the photo]

[Dwight in Toronto]

After all the great input from everyone here, ordered two packs of prewired 0402 LED’s (5 white, 5 red) from CMR Products back on November 28th, with “5 to 10 day delivery”. 

Enquired at the 15 day mark … “we were short one package - shipping today”. 

It’s been 28 days since the initial order, still waiting.  Sigh.

[Dwight in Toronto]

All is good - the 0402 led’s arrived today.  Holy schmoly, are they ever SMALL! 
Looking forward to playing with them.

[peteski]

All is good - the 0402 led’s arrived today.  Holy schmoly, are they ever SMALL! 
Looking forward to playing with them.

You should see 0201s - they are half size of 0402s. 

[Dwight in Toronto]

I wonder if they might be 0201’s?   They called them “pico” sized on the website - 1mm x .5mm. 

Pete - any special precautions or whatever to be aware of?  I’m planning to use them with 1K smd resistors and driven in conjunction with ESU N scale decoder AUX powered outputs (eg - Micro, Nano, 58741).

[peteski]

I wonder if they might be 0201’s?   They called them “pico” sized on the website - 1mm x .5mm. 

Pete - any special precautions or whatever to be aware of?  I’m planning to use them with 1K smd resistors and driven in conjunction with ESU N scale decoder AUX powered outputs (eg - Micro, Nano, 58741).

Not really. Other than having smaller package, the LED die inside is similar to what is used in larger LEDs.  Standard white LED handling is recommended.  Those usually have operating current of 5mA so you might want to use larger value resistor.

For example if your decoder's "blue" +U voltage is 12V, the average white LED has a voltage drop of around 3V then 1k resistor would pass (12-3)/1000=0.009A or 9mA.  To figure out a value resistor for 5mA or 0.005A: (12-3)/0.005=1800 or 1.8k ohms.

I don't  really follow those "micro", "nano", "pico" size descriptions.  The industry standard numerical size definitions are easy to grasp and much clearer to me.



I'm used to the Imperial sizes, but metric is just as intuitive.  The 0201 LED footprint is 0.020" X 0.010", or in metric it is 0603 0.6mm x 0.3mm. See how the actual dimensions are part of the size designation?

When I'm buying a 0402 LED I know exactly how small it will be.  If I'm buying a "nano" size LED I don't instantly know how small it will be.  Since I usually buy my LEDs from electronic suppliers, they don't use those arbitrary names.


If you are curious, there are prewired 0201 LEDs available on eBay. Here is one of many listings: https://www.ebay.com/itm/255084670796

[Dwight in Toronto]

Thanks a bunch.  The led’s didn’t come with any voltage drop nor current specs; no supplementary info at all, in fact. 
I bought a 5-pack of ‘bright white’ and a 5-pack of red.  Maybe 2K resistors would be better.

They are supposedly 1mm x .5mm, so I guess 1005 metric/0402 Imperial.

I’ll probably get around to playing with them over the holidays.  First up is fitting a few into the front of an N scale Athearn F59PHI … two white ones for alternating ditch lights on sounding the horn, and two solid red (right beside the ditch lights) that come on in reverse/pusher mode.  Using an ESU Micro for this.

Not looking forward to dealing with the birds nest of magnet wires!