Lighting Trains

[cteno4]

 

44 minutes ago, gavino200 said:

..but could it be that this is a three pin voltage regulator seen of the type posted by Chad. Jeff may have answered this question earlier, but I had assumed he was reasoning deductively rather than recognizing a component by sight.

 

 

I was going by the look of the component as you can sort of see the big single large heat sink on the other side side

 

https://www.ebay.com/itm/10X-AMS1117-5-0-5V-LDO-SOT-223-Voltage-Regulator-10Pcs-SHIPTODAY-New-power-chip/182539990870?hash=item2a803b3756:g:CjcAAOSw3ydV7WIR:rk:7:pf:0

 

basically these drop the voltage to 5v then as chad suggests you could attach to a 5v led strip.

 

the 5v led strips are just a row of leds in parallel each with a drop down resistor for each led.

 

you could put a resistor before the strip to reduce the current further to dim the strip

 

caps could go across the 5v at the strip connection points as in your 12v design. these could be 16v or 10v caps as you are now down at 5v after the voltage regulator.

 

ceramic caps at 10uf

 

basically 

 

rectifier -- power regulator  -- dimming resistor -- cap(s) -- strip -- caps(s)

 

downside is that this circuit requires about 6.5v+ to start up (you loose a volt or so in the rectifier and power regulator needs like almost 5.5v before it starts to give like 4v for the led strip to start lighting), so for dc its after your train is going. constant current chip will get going more at like 4.2v. but for dcc this is no worries!

 

there are 3.3v power regulators as well but they are right at the forward voltage of white leds so im not sure if enough to drive or not. this would then make it start up at closer to 5v for dc. going to have to get some 3.3v power regulators and play with this.

 

btw rectifier is needed for lighting on dc or dcc as dc you need it for when you reverse the train and for dcc to rectify ac to dc.

 

you also need at least 3v or so to light white leds so you cant go below that in your power for it.

 

in general i like 5v for leds as its not as much to drop, as the excess is just getting burned up in heat in the resistor. 5v is also so ubiquitous for power supplies, transformers (up or down), battery packs etc.

 

they may be running the leds in straight parallel w/o a dropdown for each led. you can do this in practice by just making sure you feed the parallel set the total of the led currents. ie 5 leds in parallel could draw 100ma (each at its 20ma max), but you need to be careful as if one of the leds draws a little more power than the others (manufacturing defects) and it becomes a runaway (electricity follows the path of least resistance first and usually as things go over current it breaks down worse until failure) so that it goes over current and fries. then there is more current for the others to handle and those go. so usually folks run leds in raw parallel (no dropdown resistor for each) at a total current that does not go over the max current for any one led. so in the strip of 5 20ma leds in a parallel strip you could run it at 20ma so each would be running at 4ma (much more in the range you want anyway for this application). if any one of the leds started drawing more worst case it would go to getting all the 20ma and not burn out but just a single led lit.

 

in practice if you use a set of decent quality leds from the same manufacturing batch they tend to work ok, but its always a risk one will loose some resistance and draw more current eventually. but again if you are below 20ma total on the supply then it at least wont fry the leds.

 

in this case my guess its probably a raw parallel set of leds thats running all of them total at 20ma from a single drop down resistor from the 5v. from the power regulator. 

 

buy one and then you can dissect it.

 

 

44 minutes ago, gavino200 said:

 

A few questions:

 

Can anyone suggest what might be an "ideal/suitable" voltage for the downstream LED/Capacitor circuit?

see above

44 minutes ago, gavino200 said:

 

Can anyone guess what the two small black components upstream of the presumed voltage regulator in the Popondetta setup are?

not enough to really see could be resistor or diode and from where it is before power regulator chip, im guessing maybe diodes

44 minutes ago, gavino200 said:

 

Is there a rectifier in the popondetta setup?

yes you would have to rectify the dc if you want it to work in both directions and for dcc to do ac to dc

44 minutes ago, gavino200 said:

 

Could the chip be a combined rectifier/voltage regulator?

i dont think so ive not seen this sort of combo. power regulators usually have shorting and reverse protection built in is what ive usually noticed. but ive not looked at power regulators carefully for a few years as i moved to looking at the constant current chips for my use with dc.

 

cheers

 

jeff

[gavino200]

Thanks for all that info!!!!

 

I figured out a few more things about the Popondetta circuit. There's a better picture of in on the Hobbysearch page.

 

https://www.1999.co.jp/eng/image/10562767/20/1

 

The two components on the left are the same as the two components on the TORM board. Kiha described them as two half diode bridges. kvp described them as three pin dual diode chips. Together they function as a rectifier. 

 

 

After the voltage regulator there are two resistors - the only resistors on the board - followed by a switch to toggle between them.

 

I'm guessing the caps are 1206 smd ceramic 5V 22uF. times 15

[gavino200]

I'm putting this in a second post for clarity as it's hugely important to me. I want to look at this circuit from an assembly point of view. 

 

1. The circuit traces on a pre-made LED strip are very thin and faint. Soldering components onto them won't be easy or reliable. I'd bet a good proportion of the strips used would be damaged. At very least it's not going to be fun. Solder pads are orders of magnitude easier to work with.

 

2. The non-LED components take up some space. This will cause some dark space at the end of a carriage. I LOVE how Popondetta have woven in a single LED into this component mix to spread out the light. Reproducing that would be very nice.

 

3.  I know I could assemble the whole thing on wire strips but it would be extremely tedious and  time consuming. There's no way I'm signing myself up to do that a thousand times. I love lighted trains but I want to spend my time on other aspects of modelling. 

 

Any thoughts on a streamlined assembly/manufacturing process. I don't really see an alternative to a printed board.

 

 

 

[chadbag]

I just downloaded some software for PCB layout (http://kicad-pcb.org)

 

Don't know if it is any good or will work for what we need, but I will try and see if we can come up with something.

[cteno4]

Yep it’s using tow dual diodes instead of a full bridge rectifier that has all 4 diodes in one chip. I think they could get smaller (and cheaper) dual diode chips than the full bridge rectifier chips.

 

yep I think it’s just how I drew out there

 

track — rectifier — dimmer resistor (on a stdt switch choose high or low) — parallel led string — prarallel cap string

 

the thing I’m not sure on is where the cap string connects in. My intuition tells me the cap string connects in before the dimmer resistors as the circuit when caps discharge would have the caps going directly into the leds if connected to the leds after the dimmer and the dimmer resistor won’t be part of the circuit and I don’t think good.

 

Soldering a lot of small smd components is not easy. Usually glued in place and float soldered on.

 

you can pretty easily solder 5 1210 size smd leds between two buss wires as well as the caps. The it’s just coming up with a way to wire up the rectifier, dimmer resistor and power regulator.

 

could just use the 5v strips and solder in your cap string to the power leads of the led string and attach to the rectifier/dimmer resistor/power regulator assembly.

 

again if you want to do 1000 of these I think talking to a professional ee might well be worth it in the long run to maybe come up with the most elegant solution both ee design, component cost and assembly wise and not do a DOH,

 

jeff

[gavino200]

15 hours ago, cteno4 said:

I think they could get smaller (and cheaper) dual diode chips than the full bridge rectifier chips.

 

That must be it. I can't think of any other advantage. 

 

Quote

 

the thing I’m not sure on is where the cap string connects in. My intuition tells me the cap string connects in before the dimmer resistors as the circuit when caps discharge would have the caps going directly into the leds if connected to the leds after the dimmer and the dimmer resistor won’t be part of the circuit and I don’t think good.

 

It's possible. There's no way to tell from these pictures. I asked @JR 500系 if he'd take some close up pictures of his. That would be very helpful.

 

Quote

 

Soldering a lot of small smd components is not easy.

 

I sort of disagree. It's not the easiest thing in the world but I think it's a lot easier than soldering smd components onto wire strips.

 

Quote

Usually glued in place and float soldered on.

 

I had a summer job doing this in a factory when I was a kid. Generally the circuit boards are mask printed with a kind of grey paste at the solder points. The components are all on reels and fed into a little pickup area. You guide a little pipette tube to the component, apply a tiny amount of suction, which pickup up the component. Then you move it to the right place on the board, place it down and release the suction. It's like being a crane driver at a container terminal, but on a minuscule scale. After that, the circuit boards are placed in an oven and baked. The paste turns to solder. That's the (old) industrial way. Probably done by robots now.

 

But I've soldered plenty of smd componants to solder pads on circuit boards manually. It's definitely fairly easy. Just not easy peasey. 

 

Quote

 

you can pretty easily solder 5 1210 size smd leds between two buss wires as well as the caps.

 

This may still be in the easi-ish range. But definitely less easy than using a board. With 15 caps this becomes definitely 'not easy'. Doable but not easy. Conducted heat tends to loosen adjacent components. 15 caps and 8 or so LED on parallel bars, would definitely stray out of 'easy' territory and well beyond the borders of PITA-land. 

 

Quote

 

The it’s just coming up with a way to wire up the rectifier, dimmer resistor and power regulator.

 

That 90% of the whole problem.

 

Quote

 

could just use the 5v strips and solder in your cap string to the power leads of the led string and attach to the rectifier/dimmer resistor/power regulator assembly.

 

I think that will add up to a good amount of dead space. The large caps are too tall, but the small caps cumulatively take up a lot of length.

 

 

Quote

 

again if you want to do 1000 of these I think talking to a professional ee might well be worth it in the long run to maybe come up with the most elegant solution both ee design, component cost and assembly wise and not do a DOH,

 

 

I think the first step would be to wire up a few basic prototypes and test them. I'd also like to get my hands on a controlled variable voltage output power supply so I could investigate the conditions under which they go poof.

Edited February 28, 2019 by gavino200

[chadbag]

I bought an air solder "iron"  (tehnically a re-working station) and some low temp solder paste.  I've been using it in some applications where the iron is too hot and clumsy.  (And learned it is not good in all applications I envisioned).  I could probably use it for this.  Once we get a prototype board I'll give it a whirl.  The "re-working" air solder stations are not expensive.

 

[gavino200]

2 hours ago, chadbag said:

I bought an air solder "iron"  (tehnically a re-working station) and some low temp solder paste.  I've been using it in some applications where the iron is too hot and clumsy.  (And learned it is not good in all applications I envisioned).  I could probably use it for this.  Once we get a prototype board I'll give it a whirl.  The "re-working" air solder stations are not expensive.

 

 

Until recently I also thought the idea was to use low heat for tiny components. Kiha informed me however, that the correct tactic is the exact opposite. Max heat so you can solder before there's time for heat conduction to damage the component. Weird right?

[gavino200]

I carried out my first real test. Video is below. The camera "perceives" the light much differently to a human retina. What's bright to the eye is full white light bright in the video. The lingering yellow glow in the video looks impressive but is barely perceptible to the eye.

 

Points learned or confirmed:

 

Jeff is right. The putting the dimmer resistor after the caps makes a big difference. 

 

Surprisingly the LEDs stay on for a decent amount of time even without a cap.

 

Without a cap it makes no difference where the resistor is placed. 

 

None of the LEDs actually brighten after disconnecting supply

 

With the eye the following are cle

 

What you see (from right to left) is 

 

1. Far right - rectifier then resistor - no cap

2. resistor then rectifier - no cap

3. Rectifier - restistor - cap - LED

4  Rectifier - 2.2K resistor - Cap - 100 ohm resistor - LED

5. Rectifier - cap - resistor - LED

6. Rectifier - four caps - resistor - LED

 

With the eye it's clear that 6 > 5 > 4 = 3 > 1 = 2

 

 

Edited February 28, 2019 by gavino200

[cteno4]

Yep the rework are mainly for removing or reflowing work on goober bits. Other issues is younhave to secure parts well or they will blow your smd parts away! 

 

Kiha is spot on, good clean, small tip and hot to get in and out fast!

 

doing a strip of caps with a piece of buss wire actually could be easy as you just line the smd caps on a piece of painters tape upside down on the bench and then lay the wire down on the tape along the bottom corner and just go down the line soldering.

 

paste and bake can work if you get the pcbs prepped for that or it’s a lot of spot pasting. Need a good oven for it as well.

 

jeff

[gavino200]

3 minutes ago, cteno4 said:

doing a strip of caps with a piece of buss wire actually could be easy as you just line the smd caps on a piece of painters tape upside down on the bench and then lay the wire down on the tape along the bottom corner and just go down the line soldering.

 

I'll give it a try. Can you send me a link to the stuff you recommend. I thought I had some but I can't find it. I could solder the rectifier in as well then cut out the intermediate segment. Same with the resistor. 

 

BTW how is a three pin voltage reducer wired? I'm guessing a one pin shared, then one of the other pins each for in and out.

 

I wonder if a simple solder, snip, swing, bend, solder would work.

 

3 minutes ago, cteno4 said:

 

paste and bake can work if you get the pcbs prepped for that or it’s a lot of spot pasting. Need a good oven for it as well.

 

 

I hadn't really even considered doing it that way. I guess it's possible to do it at home. I'm sure my wife would be delighted when I told her is was putting lead paste in the oven. 

[cteno4]

12 minutes ago, gavino200 said:

Jeff is right. The putting the dimmer resistor after the caps makes a big difference. 

 

Ok I wasn’t crazy! Once the track is disconnected the if dimmer resistor upstream ofmthe caps it won’t be in the circuit. Good to see the dimmer resistor limiting the current spreads out the discharge. Now how does it on dirty track!

 

12 minutes ago, gavino200 said:

 

Surprisingly the LEDs stay on for a decent amount of time even without a cap.

 

I think this is due to the fact white leds use a phosphorescent coating that is making the final light white (it’s not pure white coming out of the diode) and this may glow a while but only really visible in the camera that exaggerates the after glow.

 

http://www.photonstartechnology.com/learn/how_leds_produce_white_light

 

12 minutes ago, gavino200 said:

 

Without a cap it makes no difference where the resistor is placed. 

 

Here the resistor is just working as a dimmer/current limiter and it does not matter where in the basic circuit it is as it will limit the current at that point (just as in a hose a pinch at any point will make the reduction if flow amount at any point in the system). Once power is off whole circuit is broken. With a cap in there you have a secondary power source that can make a new circuit when the track power is cut, thus there it can matter where the resistor is new cap discharge phase circuit with track power cut.

 

12 minutes ago, gavino200 said:

None of the LEDs actually brighten after disconnecting supply

 

Cap may not have enough charge to brighten the 6 leds. Maybe with more caps, not sure.

 

jeff

[chadbag]

The #4 with the two resistors reversed is how most of the examples I’ve seen online are set ip

 

rectifier -> 100 ohm -> cap -> limiting cap (2.2k) -> LEDs

 

The 100 Ohm limits the inrush to the cap

 

 

[cteno4]

Buss wire is just copper wire that’s been pretinned. It’s the same stuff as component leads like traditional resistors. For smaller amounts it’s actually cheaper to get 1000 1/8 watt cheap resistors on ebay for a couple of bucks! But that’s if you only need 1” pieces! 

 

You can buy it in rolls, but not used as much anymore so not as cheap anymore.

 

yes center is usually ground and others are Vin and Vout +.  Spec sheet is your friend

 

http://www.advanced-monolithic.com/pdf/ds1117.pdf

 

yeah not the best, but I think you will need one with a lot better heat control than your oven does! You can hack your own.

 

http://www.whizoo.com/reflowoven

https://www.instructables.com/id/Making-A-SMD-Reflow-Oven/

 

or pick up a used one

 

https://www.ebay.com/itm/Vitronics-SMR-820A-SMT-Reflow-Oven/113666784094?hash=item1a77117b5e:g:BqgAAOSw76JcG-Md

 

or small one new for $200, cheaper than crossing your wire and baking lead crusted brownies... actually there is lead free solder paste these days.

 

jeff

[cteno4]

2 minutes ago, chadbag said:

The #4 with the two resistors reversed is how most of the examples I’ve seen online are set ip

 

rectifier -> 100 ohm -> cap -> limiting cap (2.2k) -> LEDs

 

The 100 Ohm limits the inrush to the cap

 

 

 

Yep this is the full design to stop the inrush. For smaller cap it may not be an issue, especially with high power of dcc. I think not limiting the inrush could cause earlier breakdown, especially the close your voltage is to the cap rating as full inrush is the most brutal chemically.

 

jeff

[gavino200]

1 hour ago, chadbag said:

The #4 with the two resistors reversed is how most of the examples I’ve seen online are set ip

 

rectifier -> 100 ohm -> cap -> limiting cap (2.2k) -> LEDs

 

The 100 Ohm limits the inrush to the cap

 

 

 

That's interesting. I wasn't trying to copy this, as I didn't even know about it. I was just curious if a smaller resistance would be enough to slow down the cap discharge. 

[gavino200]

1 hour ago, cteno4 said:

Buss wire is just copper wire that’s been pretinned. It’s the same stuff as component leads like traditional resistors. For smaller amounts it’s actually cheaper to get 1000 1/8 watt cheap resistors on ebay for a couple of bucks! But that’s if you only need 1” pieces! 

 

 

Thanks. I ordered some.

[Ochanomizu]

Hello Gavino200,

 

What size Cap you are using in the video above?

[chadbag]

6 hours ago, gavino200 said:

 

Until recently I also thought the idea was to use low heat for tiny components. Kiha informed me however, that the correct tactic is the exact opposite. Max heat so you can solder before there's time for heat conduction to damage the component. Weird right?

 

Yes and No.  Kiha is 100% correct.  However, what he is talking about is relative heat.  Relative to the melting point of the solder.  If your solder melts at 640 deg F and you set your iron at 650 deg F , it will be slower to heat up the items, melt the solder, etc.  A hotter iron will take care of things faster.

 

However, if only using a solder that melts at 278 deg F, you can use a lower heat iron and get the same results as Kiha is talking about.

 

The low temperature solder paste I have melts at 278 deg F so if you set your iron (or heat gun) at say 350 deg F or 400 deg F you have an overall lower temperature but get the same quick work as the higher temperature iron with normal high temp solder (like we normally use).

 

I've actually used the low temp paste with my iron set at a much lower temperature than for normal solder but much higher than the paste and it works really well for overall much less heat in the system.

 

I think the airgun set at 350 or 400 for this paste will work well for these SMD components and the air stream is very slow so it doesn't blow things away.   I've used it to solder some of the decoders to the JNS ersatz EM13

 

5 hours ago, cteno4 said:

Yep the rework are mainly for removing or reflowing work on goober bits. Other issues is younhave to secure parts well or they will blow your smd parts away! 

 

Kiha is spot on, good clean, small tip and hot to get in and out fast!

 

Yes, but it is relative temperature. The air gun is low volume air and so I think would work well putting these SMD components on a board.  I'll have to try eventually.

Edited March 1, 2019 by chadbag

[gavino200]

On 2/28/2019 at 2:12 PM, gavino200 said:

 

17 hours ago, chadbag said:

 

The low temperature solder paste I have melts at 278 deg F so if you set your iron (or heat gun) at say 350 deg F or 400 deg F you have an overall lower temperature but get the same quick work as the higher temperature iron with normal high temp solder (like we normally use).

 

Interesting. That must be the stuff I was talking about a few posts ago. See below. You could probably make a stencil with an xacto blade and some card, and place the paste precisely on the solder pads of a board. then you simply  lay the smd components down on them and heat to turn it to solder. Otherwise I could imagine it being a bit messy.

 

 

 

 

 

 

 

I had a summer job doing this in a factory when I was a kid. Generally the circuit boards are mask printed with a kind of grey paste at the solder points. The components are all on reels and fed into a little pickup area. You guide a little pipette tube to the component, apply a tiny amount of suction, which pickup up the component. Then you move it to the right place on the board, place it down and release the suction. It's like being a crane driver at a container terminal, but on a minuscule scale. After that, the circuit boards are placed in an oven and baked. The paste turns to solder. That's the (old) industrial way. Probably done by robots now.

 

 

[gavino200]

19 hours ago, Ochanomizu said:

Hello Gavino200,

 

What size Cap you are using in the video above?

 

The cap is a sise E 40V 220uF Tantalum SMD.  It looks ideal in the pictures but it's actually too tall/ high to be truly convenient for N-scale. There isn't enough space for it between the roof and the plastic interior details. It's a pain to install one of them. More than one would be very difficult. That's why we're looking for a way to drop the voltage to 5v so we can use smaller sized capacitor. The test was to work out a few things that we had been discussing theoretically. 

 

If you have ideas about this project I'd love to hear your input.

[gavino200]

23 hours ago, cteno4 said:

 

Ok I wasn’t crazy! Once the track is disconnected the if dimmer resistor upstream ofmthe caps it won’t be in the circuit. Good to see the dimmer resistor limiting the current spreads out the discharge. Now how does it on dirty track!

 

 

Y'know I had a feeling your were right about this. But I was really hoping you weren't. If the Caps could be placed after the resistor then they could have been placed anywhere. Especially convenient would have been to just fill up the space between the LEDs with rows of caps. 

 

With need for a resistor between the caps and the LEDs the circuit design becomes a bit of a head wrecker without creating a lot of dead space at one end of the board/rail. 

 

A solution might be to interpose one or two LEDs on fine wire from between the caps, taking supply from the rails downstream after the resistor.

[chadbag]

8 minutes ago, gavino200 said:

You could probably make a stencil with an xacto blade and some card, and place the paste precisely on the solder pads of a board. then you simply  lay the smd components down on them and heat to turn it to solder.

 

You don't need a template.  Just put a splotch on each pad (I used an old xacto blade).  As it heats it spreads a little and stays on the pad as the pad heats up.

 

You can also use an iron with it if you don't like the heat gun.  Just set it to a lower temp if you have an adjustable one (well worth getting a soldering station with adjustable temp) (lower than what you use for normal solder).

 

[chadbag]

3 minutes ago, gavino200 said:

 

Y'know I had a feeling your were right about this. But I was really hoping you weren't. If the Caps could be placed after the resistor then they could have been placed anywhere. Especially convenient would have been to just fill up the space between the LEDs with rows of caps. 

 

With need for a resistor between the caps and the LEDs the circuit design becomes a bit of a head wrecker without creating a lot of dead space at one end of the board/rail. 

 

A solution might be to interpose one or two LEDs on fine wire from between the caps, taking supply from the rails downstream after the resistor.

 

I am going to make a go at designing the PCB this weekend for a first pass.  The good thing is you can run traces this way and that (look at your Pop.... board pics) so that you can do it right and not have the dead space.

[gavino200]

9 minutes ago, chadbag said:

 

I am going to make a go at designing the PCB this weekend for a first pass.  The good thing is you can run traces this way and that (look at your Pop.... board pics) so that you can do it right and not have the dead space.

 

Awesome. Time for exit stage left. (to a project thread)