(MicroLumina) current limiters?

[Bernd]

Bernd, I'd trust the manufacturer's spec unless something blew up when I followed it. But there are a lot of oddball parts out there; I'd always verify any general result from web search. And AI can be completely sure about a totally bogus result, so I treat it like that type of person.

I don't know what's so hard about figuring this out.

What you should find is that red, green, or yellow LEDs have relatively low forward voltage ranging from 1.6-2.2V. However, blue and white LEDs can begin conducting from 2.5-4V.

This gives you a range of voltages used by the various colored LED's. That chart I linked to gets you down to a closer voltage for the color you are using. Besides an LED is current controlled and not voltage controlled. Filament bulbs are voltage controlled and not amperage controlled. You can take a 12 volt bulb and hook it to a 12 volt car battery capable to 200amps or more cranking the engine over yet the bulb doesn't blow. You can also hook an LED (.025 Ma)to that same car battery with a (12v/.025Ma = 480 ohms)or higher (510 ohm) resistor with out blowing it up.

I'd go with the higher voltage with what ever color LED you are using and the higher Ma suggested for that color and then work my way down till I get the brightness I want. Problem solved. Nothing magical about it. Just like figuring out how to set your CV parameters on DCC.

Bernd

[deemery]

I spent some time looking at a -bunch- of tech data sheets for the 3 common sizes of Surface Mount (SMD) White LEDs.  

0603. Footprint: 1.60 x 0.80 x 0.40mm.
0805. Footprint: 2.00 x 1.25 x 0.80mm.
1206. Footprint: 3.20 x 1.60 x 1.10mm.

This is not a scientific sample, but the average forward voltage for 0603 and 0805 was pretty common around 3v. But for 1206, here was more variation.  It's perhaps unfortunate the first one I looked at showed Vmin 1.8, Vmax 2.4.  https://www.farnell.com/datasheets/3497852.pdf  Others showed (min/max) 2.8 - 3.8, 2.8 - 3.7, and 2.8 - 3.4.  So as long as I don't happen to hit a device from that first 1206 vendor, I should be OK assuming a 1206 LED should accept 3.0v.  

Bernd, this is why I was making this "harder than it should be".  And why that article you sent earlier that asserted a single common value for Vforward wasn't matching what I was reading before I did a bit more research.

dave

[Bernd]

Dave,

I believe you want to wire your lights in series, correct?

I'd wire them in parallel. Why? If one of the LEDs dies the others will also go out. Now you need to find which one gave up the ghost. Think of it like looking for the bulb that blew in the Christmas tree lights in a string of many. Just a suggestion to contemplate.

Bernd

[jbvb]

My first LED installations are about 30 years old, they all still work except for a couple where my error put the wrong voltage to them after they were in service. AFAIK the greedheads haven't yet corrupted individual LEDs with "planned obsolescence" like the little nick in the filament of both incandescent bulbs and vacuum tubes. So I don't worry about diagnosing failed LEDs like I do with incandescents.

[deemery]

I did a bit of web research on LED failures.  Seems they follow the relatively common "bathtub model" where there are initial failures due to manufacturing problems, etc, a long time with very few failures, and eventually an increase of failures as they start to reach end-of-life.  See https://www.osram.com/Graphics/XPic6/00102625_0.pdf for a good discussion.

So that tells me it would be A Good Thing after I assemble my light string, to let it 'burn in' for a day or so before installing it, and once it's installed, to not worry.  

dave

[deemery]

Well, I got the 4 LEDs soldered up (with sufficient cursing).  And that includes resoldering a wire back onto the LED when I accidentally pulled it off (while working on the heat shrink tubing...) 

I set the power supply for 12v, and then started at about 0.008a.  Here's the result at .012a

So if I've done the calculations correctly, R=12/.012 or 1k ohms.   And that current is less than the 20ma/.02 for LEDs, right?

dave

[Bernd]

That could have been done cheaper with a 12volt power supply and a couple of resistors plus some math.

https://www.amazon.com/Variable-ENGINDOT-Adjustable-Adjustment-Alligator/dp/B09KMS74PT

Bernd

[deemery]

That could have been done cheaper with a 12volt power supply and a couple of resistors plus some math.

https://www.amazon.com/Variable-ENGINDOT-Adjustable-Adjustment-Alligator/dp/B09KMS74PT

Bernd

I'm sure you've used an expensive tool that you had where there was a cheaper alternative, too!      But it worked, and I learned from the experience.  Runs in my mind, though, that power supply was significantly cheaper when I bought it.

dave

[Bernd]

I'm sure you've used an expensive tool that you had where there was a cheaper alternative, too!   

Yes I have. I'm sure the Carvera CNC machine comes to your mind. That's a multi material use device, as where that power supply is a single use device.

I had to research what that "MicroLumina" product was. Looks like it can be used if don't know what your power supply voltage is or varies while in use. I can't see using that if one knows how much voltage a power supply puts out.

B~

[deemery]

The "MicroLumina device" is just a current limiter for LEDs.  But that consumes voltage (about 3v) when it's put in the circuit.  So with a current limiter, I could power 3 LEDs on a 12v circuit.   Without one, I get 4 LEDs on 12v.  

I bought that power supply when I did my Arduino project animating a ball signal. 

dave

[Bernd]

The "MicroLumina device" is just a current limiter for LEDs.  But that consumes voltage (about 3v) when it's put in the circuit.  So with a current limiter, I could power 3 LEDs on a 12v circuit.   Without one, I get 4 LEDs on 12v.

B~

[ACL1504]

The "MicroLumina device" is just a current limiter for LEDs.  But that consumes voltage (about 3v) when it's put in the circuit.  So with a current limiter, I could power 3 LEDs on a 12v circuit.  Without one, I get 4 LEDs on 12v. 

I bought that power supply when I did my Arduino project animating a ball signal.

dave

Dave,

The great thing about the ML Current Limiter is that it will handle from 9 - 90 volts, per Bill Satore when he gave a clinic at one of the Modeler's EXPO.

Tom