More LED stuff

[RR_Mel]

I have 5 of the SMTL4s soldered up (18 more to go), I have checked the currents on all five.  I have settled on 2.5ma for red, 4ma for green and 10.5ma for yellow to get equal brightness on all four colors. 

 

I’m driving them with an Arduino MEGA so using the same 5 volt power supply as the LED source I ended up using a 1KΩ series resistor for red, 220Ω for yellow and 560Ω for green.  Each color has a slightly different operating voltage requiring slight different resistor values.  Using standard 5% ⅛ watt resistor values the current is about ± .1ma. 

 

There .68 volt drop through the Arduino shunt leaving 4.32 volts to the LED/series resistor.

 

The depth of the NJI signal head is .185” and a chopped off defused lens is .1” leaving the need of a .085” Acrylic spacer.  To have the lens slightly out of the head I’m going with a .1” spacer between the lens and the face of the LED.

 

Problem solved!  I now have a very good looking HO scale three color searchlight signal.

 

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[Bayfield Transfer Railway]

Nice yellow.

 

[RR_Mel]

Well between my Arthritis and two power outages I haven’t got much done.  I have tested the three I soldered the wires to and all three look very good with the defused lens and 5ma on the red and green and 10 ma on the yellow.

 

 

 

 

The lens is 3mm diffused chopped off of a 3mm Bi-Color LED and glued to the SMTL4.

 

I’m driving them at 4.3 volts, simulated output of the Arduino MEGA.  They are common Anode and the MEGA is switched ground.

 

So the SMTL4-RGY is a go for me.  They will slip into the NJI HO Searchlight Head.  I make my signals from K&S Brass tubing using the NJI heads as a go-by.

 

The only difficulty is soldering the Litz wire, it’s too small and too hard to manage.  I ended up using a dob of AC on both ends of the wire (12” finished) then putting one end in the chuck of my 220 RPM cordless drill and clamping the other end in my bench vice winding them tight.  When the wire relaxes it no longer gets in the way of soldering.

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[RR_Mel]

I just finished my third using surgical clamps for holding the LED and the surgical clamps in my Panavice, that went OK.  Actually I like the tape better, easier to change positions for soldering.

 

I don’t have any of the self closing tweezers, I need to get several.  I’ve never had a use for them until now.

 

The three I just finished have better yellows, the first one might have been defective.  All three colors are well balanced at about 8ma.  The yellow voltage isn’t the same so it takes a different resistor than the red and green.

 

I need to hook up several to my controller and see what they look like in operation.

 

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[BATMAN]

Mel, I put that #38 wire in a clothes peg and hold the clothes peg, it is then easily handled. I put the LED in self-closing tweezers and put the tweezers in a vice. Yesterday I bought some things to make a jig to hold the LEDs after seeing what a You-Tuber had done.

[RR_Mel]

This was actually easier than painting my HO figures.  I used hand warmers for about an hour to calm down my Arthritic finger joints before I started this task.

 

It was a lot easier than I thought it would be.

 

X5 flip down glasses really help.

 

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[rrebell]

I could not do this work when I was young, you are amazing.

[RR_Mel]

My report on the SMTL4-RGY Tri-Color LED.  They work great!!!!

 

The Red is a very good Red and at 3ma is very bright.

 

The Green is also a very good Green color and looks equal in brightness to the Red also running at 3ma.

 

The Yellow is a bit flakey on color and much dimmer than the Red and Green at 3ma.  I gradually increased the current to 10ma and it balanced out very close to the Red and Green in brightness as well as a much better looking Yellow.

 

Soldering to the LED was much easier than I expected.  I did have problems working with the #38 Litz wire, it’s small size and my fat fingers didn’t do well at all.  The only way I could handle the itty bitty wire was to solder one end to the three test resistors glued together.  I finally twisted the four wires together and put a dob of CA near the LED end leaving enough wire free to solder to the LED.

 

I used a wrap of 1½ wide masking tape around a small block of wood sticky side out.  I pressed the wood block onto my cutting mat then pressed the LED to the tape as a holder while soldering, that worked out very good.

 

I put a dob of non corrosive soldering paste on each pad of the LED then just touched the soldering iron to each pad, less than a second and the pads took the solder very nicely.  I stripped the Litz wire using my thumb nail about 1/16 and tinned them.  I trimmed the soldered ends back to about 1/32” then just touched the soldering iron tip to the wire at the LED solder pads, again less than a second.

 

After testing to make sure all three colors were happy I put a dob of CA on the back of the LED to secure the wires.

 

I experimented with chopped off 3mm LED lenses for an extended lens for the SMTL4.  The LED has a very small almost flat clear lens.  I tried both clear and defused lenses, clear worked very good for Red and Green but Yellow was very poor.  The defused lens looks great with all three colors.

 

I’ll post some pictures later, I forgot to charge my camera battery.

 

I dinged two LEDs early on, both from not anchoring the Litz wires and the LED side of the wires touched the supply line bypassing the resistor, they actually pop when that happens.  Everything went as smooth as silk after taking care of the wire problem.

 

 

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[mbinsewi]

RR_Mel

And No Mike they came that way.

OK, I get it, when you said you added some color, I thought it meant the leds.

Mike.

[RR_Mel]

I haven’t messed around with these yet but the specs look pretty good.  And No Mike they came that way.

 

The typical SMT LEDs I’ve been using have 60 limens and they are way too bright at 20 ma, I normally run them at 4 to 5 ma so these should do OK for searchlight heads at 12 lumens.

 

The SMT tail light on my heavyweight observation car is too bright at 3 ma.

 

This cool weather has really dinged my finger joints, even working with the soldering iron to warm them up its tough to solder something that small.  I’m going to give it a shot this afternoon.

 

EDIT:

 

Before I removed my original 3mm bi-color LEDs from the signal heads I checked the current, they were drawing 4ma and were quite bright. 

 

And by the way the reason for removing my working signals is that I built it up years ago using common cathode LEDs and I wanted to go with switched ground using my MEGA controller.  I was using the signal mast for ground and decided to go with four wires to each LED this time using common anode LEDs, I didn’t like idea of having the masts with positive voltage on them next to the tacks. 

 

No voltage or gorund on the mast sounds so much better, the new LEDs fed with four wires sounds much better.

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[mbinsewi]

Wow Mel!  You put those tiny little red, green and yellow chips in that LED?  

You amaze me Mel.

Mike.

[wvg_ca]

the emitted light is fairly even between the colours ??

[RR_Mel]

I didn’t know whether to resurrect my orignal post of December 26 or go with a new one so after some thought here goes a new one.

 

My original post was “Having a problem finding a good working Bi-Color LED”.  Well the general consentience was to go with the LEDs from one of the model railroad sources that had three color micro LEDs.  Well I’m a retired tight wad with a small model railroad budget and . . .  I just like to experiment or dink around with everything I do.

 

I went into search mode for several weeks then gave up.  I bought a few more worthless bi-color LEDs so I have a lot of 3mm LEDs I can chop up for their lenses.

 

After my cataract surgery last month I feel better about getting back to my signaling project, I have depth of vision again.  I built up a few more Mel Tri-color LEDs and went back in search mode.

 

I found one!  It’s made by BIVAR and sold at Digikey and Mouser, Mouser had a better price with a price break at 25.  I only have 16 single target searchlight heads so Mouser it was.  I got 25 delivered for $32 so the price is right at $1.28 per LED and $9 for four colors of #38 Litz wire from China.  

 

The LED part number is SMTL4-RGY.  Here is a link to the datasheet.

 

https://www.bivar.com/portals/0/products/SMTL4-RGY.pdf

 

This is what they look like from Mouser, they came yesterday.

 

 

 

I added a bit of color to the one below

 

 

 

I’m having a bit of trouble using my soldering iron do to my Arthritis but as soon as I can solder without destroying one I’m going to “Git-R-Done”.

 

 

 

Mel

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.