1/16 watt = x ma?

watts = amps x volts

amps = watts / volts

for some reason I kept thinking VIR or WIV and couldn't remember anything else?

P=IE  Power (watts) equals I (amps) times EMF (volts)

(convert fraction to decimal : 1/16 = .0625)

.0625 = I x 3

.0625/3 = I = .021 amps = 21 milliamps per LED

So you are assuming that the micro LED is lit properly with 3 volts? I don't see where that was determined.

Remember Chuck, LED's are current mode devices.  You need to limit current, but around 3V is a good figure to use for white or blue LED's.

Engineer-Joe posted:

I want to buy some more micro LEDs. I would get some bigger ones but I have a limit on how many LEDs can attach to one function output on the MTH PS3 board. It was posted no more than 3 LEDs per channel.

To be clear, when you say "micro" LED are you referring to a physically smaller package with the assumption it consumes less power?

Can you recall the post where it says no more than 3 LEDs per channel?

I recall there is such a limitation in PS2 with incandescent bulbs.  But bulbs are voltage devices driven by a controlled voltage.  For example, when you added a 2nd bulb the two bulbs would essentially be at the same brightness.  But in PS3 with LEDs, a particular output is driven by a controlled current.  If you add a 2nd (or 3rd or 4th) LED there should be no expectation that the additional LEDs will be at the same brightness; that is, the current will split and each LED will get some fraction of the original current.

AFAIK, the effective current to a given PS3 LED output channel is a parameter stored in the soundset.  The conundrum, if you want to call it that, is when you have two (or more) LEDs wired in parallel.  If one or more LEDs goes out which could be from a broken wire, then the remaining LEDs will have to "absorb" the available current.  MTH surely realizes this when setting the current to a multi-LED channel.  The point being I find it unlikely you'll be able add LEDs and get 60mA (or whatever) out of PS3 LED output that was configured to drive 1 LED.  Note this is different than PS2 bulbs where a voltage presented to the remaining bulbs remains the same when one goes out. 

I guess it depends on what you're trying to accomplish.  So, what are you trying to accomplish?

Stan, George (GGG) has stated that the outputs handle multiple LED's.  I'm also curious how they regulate this feature.  It's hard to imagine they do it based strictly on voltage, but as you say, regulating current would have to be done somewhat intelligently.

Thank you Stan.

I am trying to add flashing, charging lights to a PS3 upgrade kit. I have to guess on this stuff as I'm not a tech. I did not know the function outputs where variable on these boards. I did note that the one chain file was called "diesel smoke" so I'm guessing that it can adjust how hardware is controlled.

 I started looking at the micro leds not only for their smaller size, but also for something that drew less current. I saw a post that stated the PS3 board still would only handle so many LEDs. I did not know that the number was set by MTH.

 So........ I have a PS3 diesel kit installed into a scratch built G scale GE evo. It is basically an all MTH product inside using their trucks and electronics. I cut the PS2 tach hole much larger to mount the PS3 Tach reader board close to the flywheel.

 More importantly, I installed the O scale GE Evo PS3 sound and chain files. Unfortunately MTH does not give out specs on what that fully means to guys like me. So I have to study an O scale model to determine what I can use. It appears that they have made custom LED panels for these charging lights. I will have roughly 40 lights inside my version. They go to 4 different circuits. So I need to put 10 LEDs on each circuit.

 Please let me know if I forgot any extra info to help, and thank you again for looking and helping.

gunrunnerjohn posted:

Remember Chuck, LED's are current mode devices.  You need to limit current, but around 3V is a good figure to use for white or blue LED's.

That was my concern, was 3 volts a good choice...I have seen the junction voltage with a proper current vary from 1.something to 2.something. Is this micro led a known and consistent product?

I truthfully don't know how they're regulating multiple LED's on the PS/3 boards, I haven't had occasion to do any research in that area.

I tried with a couple of people to get my hands on the "stock" lights. No luck. They appear to be tiny LEDs inside of greenish plastic light bars?

https://mthtrains.com/20-20506-1

"Flashing LED Charging Lights"

I also looked at the tiny battery strings of LEDs at the stores. I figured that the SMD's would be better suited?

Somewhere I have to take a stab at it. Part of scratch building is deciding how you're going to capture what the real one has. I first thought they were in the side boxes and just covered with GELs for light color.

I now see both side lights that the O scale manufacturer's made, and light strips underneath.

I originally looked at tiny SMD LEDs to have running lights on engines. Here's and example from someone else: (starts at 5:06)

You could tap a place like OSH Park and make a PCB that had all the SMT LED's mounted, it would make the job of mounting them and wiring them a bunch easier.

I thought the O EVO used a custom circuit board with smarts (electronics) for the chase sequence depending on if charging or discharging?  In other words, it is not co-opting "standard" LED outputs for markers, ditch, beacon, whatever and somehow programming those to flash in a left-to-right or right-to-left chase sequence?

If this is correct then it seems to scale 1/48 to 1/32, you'd be doing a heck of a lot of wiring to take an existing 1/48 chase sequence circuit board to increase physical dimensions 50% to scale it up to G-gauge.

I heard that about the PS2 model. I think that got changed with the PS3. I don't have any info more than just a guess. So I listen for hints!

When I ask specific questions or try to buy certain parts, things get quiet.

To find out how that sound file and chain file would work in a PS/3 board, the easiest way it to load it into a board using the PS/3 test set.  It has LED's for all the outputs, and you could see if the chase lights are directly driven.

Well ...GRJ and Stan, Did you see my video? As you thought before, the PS3 board does provide the chase for the lights. Now maybe that drives another board?

Maybe there's an extra board just to handle the wiring?

I do have the PS2 version and never opened it up. I imagine it might be different back then.

I thought we had decided that it did drive the lights.  George guessed the extra board is just an interconnect board for all the wiring, I suspect he's right.  I'll bet a PS/2 model would have to have extra logic.

Joe, I'm a bit confused on what you actually have.  Your video shows LEDs operating in the chase-sequence.  If you are using a PS3 board set, does that mean you found the "magic" 4 LED output channels which are assigned to directly drive the LEDs with no additional circuitry?  By no additional circuitry I mean you only need to add interconnect wiring to distribute each output to 10 parallel LEDs - assuming by 40 LEDs you mean 4 channels x 10 LEDs/channel.

As I understand it, you loaded a O-gauge EVO soundset into your PS3 board?  So if MTH upgraded the PS3 board to perform the chase-sequence (knowing when to reverse direction), then do they also sell the O-gauge LED modules?  It seems you simply need to scale-up their LED module 50% to fit your G-gauge shell?  If you don't want to go the OSH Park route, you can get really-thin (1/64" thick) circuit board material that can be cut with scissors.  You can then scrape off the copper as needed with a hobby-knife to make your interconnections and mount the LEDs.  You are essentially making something like the 12V LED light strips - that is, thin, long, multiple parallel LED circuits.

So if the PS3 board indeed supports directly driving chase LEDs for the EVO, has MTH produced a PS3 O-gauge version (presumably not a G-gauge one since this would make this discussion moot)?  I'd think they would still need some kind of buffering circuit to drive 10 LEDs (or whatever) per channel but that's just speculation.

Clearly, a plain PS/3 board is able to drive the charging lights.   One interesting point, it appears that they skip one LED when moving and a different one when stopped, very odd.

That's exactly what David Minarik posted a few weeks back...

DAVID MINARIKMEMBER DIGITAL SUBSCRIBERFORUM SPONSOR

8/18/17 9:52 AM

Casey Jones2 posted:

That's exactly what David Minarik posted a few weeks back...

Sorry Dave, didn't see yours or it would have saved me the trouble.

Someone still needs to document exactly which PS3 LED outputs you need to tap.  GGG's answer is not definitive - unless someone posts a photo of this "junction board", I'm still speculating there might be the need for some kind of buffering (additional active components) if you are indeed driving 10 LEDs from each PS3 LED output.  For G gauge, it stands to reason that each LED must be proportionally brighter simply from the larger scale (G vs. O) and hence require more current.

Buffering the output is not rocket science if that's indeed what's needed (say, less than $1 in parts).  Just need to bring 5V DC power/ground from the PS3 harness to the "junction board".

Other than seeing one in the flesh, I don't know how to determine how many LED's the PS/3 board will drive.  Sounds like a science project for someone.