JNSF DIY lighting project (PCB based)

[chadbag]

This is the base post for the thread for the DIY lighting project PCB board.  I am going to come up with an initial try this weekend if I can.

 

I am going to try and make it flexible so you can use 0805 or 1206 sized components (LEDs, ceramic caps), as well as a tantalum cap.  Also with or without a voltage regulator (and support both a 3 pin DIP? and SMD style).  And make it so you can break off the board ends to make different length boards (with a place to wire a jumper to complete the circuit).

 

About how far apart do we want the LEDs to be?  How wide should the board be?  A Tomix factory board I have is about 3/8" (about 9.5mm) wide.

 

Generally the circuit will be like

 

rectifier (optional)  -- voltage regulator (optional -- you can run the board at 5V or 12V or whatever you want) -- resistor (inrush like 100 ohm or whatever you want) -- caps (up to 10 ceramic or one tantulum) -- dimming resistor -- LEDs

 

@Kiha66   Does that look reasonable?

 

For the optionality of the rectifier and/or voltage regulator there will be multiple "start points"

 

 

Edited March 2, 2019 by chadbag

[Kiha66]

Seems pretty good!  I'm excited to see where this project goes.  If you have the parts on hand its good to make a test piece before actually building the production board so you can find what obvious connection your missed. 😁 

 

[Sheffie]

Random question. Does anyone know what sort of length of production run is viable for paying a third party to manufacture circuit boards? Obviously there will be a steep quantity/price-per-unit curve... I'm just wondering how good modern short-run production facilities might be these days. A thousand items might be enough for it to be cost-effective.

 

(Note to self: ask at work about this.)

Edited March 2, 2019 by Sheffie

[chadbag]

Yes, I will wire up some samples but the board is meant to be flexible, supporting 12V or 5V (or whatever voltage regulator you want) and multiple cap and resistor values and number of LEDs.

 

With or without a voltage regulator and with or without a rectifier.  Ie, for those running on DC or DCC without a decoder, they can run with rectifier and those running from a decoder can leave the rectifier off.  And then add the voltage regulator or not depending on what voltage they want to run.

[chadbag]

1 minute ago, Sheffie said:

Random question. Does anyone know what sort of length of production run is viable for paying a third party to manufacture circuit boards? Obviously there will be a steep quantity/price-per-unit curve... I'm just wondering how good modern short-run production facilities might be these days. A thousand items might be enough for it to be cost-effective.

 

(Note to self: ask at work about this.)

 

The contract places are pretty cheap.  I was able to get 10 x 2 (2 different boards, 10 each) of the EM13 ersatz board (see elsewhere in this forum) from a place in China for about $25 delivered.  Don't know how this will compare.

 

[chadbag]

I just ordered a few 1206 and 0805 LEDs and caps, and a few different voltage regulators, to use as test pieces in the design of the board.  From US sources.  While I await the stuff already ordered (in larger numbers) from China/HK.

 

[gavino200]

3 hours ago, chadbag said:

This is the base post for the thread for the DIY lighting project PCB board.  I am going to come up with an initial try this weekend if I can.

 

Awesome

 

3 hours ago, chadbag said:

 

I am going to try and make it flexible so you can use 0805 or 1206 sized components (LEDs, ceramic caps), as well as a tantalum cap.  Also with or without a voltage regulator (and support both a 3 pin DIP? and SMD style).  And make it so you can break off the board ends to make different length boards (with a place to wire a jumper to complete the circuit).

 

I have a few opinions on this (shocker, I know)

 

For the most part I think 1206 components will be small enough, and a re a lot easier to work with than 0805.  

 

I'd have a preference for just killing the idea of using tantulum caps. Their vertical dimension is too tall. The strip won't fit very many models if any. Also the size difference between tantalums and ceramics is massive. They won't fit on the same footprint/solder pads. I've ordered a bunch of these. But I'm going to resell them on ebay when they arrive. 

 

The voltage regulator is necessary if ceramic caps are to be used. Also the rectifier is necessary. The only advantage to not using them is that the strip could be used as a simple non capacitor strip or DC strip. However, in either of these cases it's much easier to just use a plain LED strip with either a resistor or a resistor/rectifier combo soldered to it. This setup can be put together in minutes. Using your masterpiece of design for such a simple use would be a total waste.

 

 

3 hours ago, chadbag said:

 

 How wide should the board be?  A Tomix factory board I have is about 3/8" (about 9.5mm) wide.

 

The thinner the better. It will be much more versatile if it's thinner.

 

3 hours ago, chadbag said:

 

Generally the circuit will be like

 

rectifier (optional)  -- voltage regulator (optional -- you can run the board at 5V or 12V or whatever you want) -- resistor (inrush like 100 ohm or whatever you want) -- caps (up to 10 ceramic or one tantulum) -- dimming resistor -- LEDs

 

@Kiha66   Does that look reasonable?

 

For the optionality of the rectifier and/or voltage regulator there will be multiple "start points"

 

 

 

Very nice. But I'd  vote for the Kiss principle. Just make a 5V/ceramic strip. Components that fit can be listed. They're cheap and easy to find.

[gavino200]

3 hours ago, Kiha66 said:

Seems pretty good!  I'm excited to see where this project goes.  If you have the parts on hand its good to make a test piece before actually building the production board so you can find what obvious connection your missed. 😁 

 

 

I couldn't agree more. A physical prototype should be made before anything is sent for production.

[gavino200]

1 hour ago, chadbag said:

I just ordered a few 1206 and 0805 LEDs and caps, and a few different voltage regulators, to use as test pieces in the design of the board.  From US sources.  While I await the stuff already ordered (in larger numbers) from China/HK.

 

 

Don't forget to get warms and brights.

[chadbag]

I have both 0805 and 1206 sized stuff here.  I think if you spaced and sized the pads correctly you should be able to use either one.  And the first set of pads could be elongated to fit the D sized Tantalum.  So really no difference but more versatile.

 

The rectifier is not necessary if you are feeding it from a decoder.   It should be possible to make both of these optional on the board so that you can use the same board for various options and components.

[chadbag]

1 minute ago, gavino200 said:

 

Don't forget to get warms and brights.

 

No worries. I got both white and warm white.

[chadbag]

What spacing for LEDs should we strive for?

 

[gavino200]

3 hours ago, chadbag said:

 

About how far apart do we want the LEDs to be?  

 

 

 

My "Dani style" strips with 1206 LEDs have an LED every 17mm

 

TORMs use 0805s or smaller and are every 11mm.

[chadbag]

10 minutes ago, gavino200 said:

 

I couldn't agree more. A physical prototype should be made before anything is sent for production.

 

Once we had a design we like I'll send off for a minimum size sample order (like 10 or 20) and we'll try them out.  If they wor we'll see what larger sized orders are and who wants some.

[gavino200]

4 minutes ago, chadbag said:

I have both 0805 and 1206 sized stuff here.  I think if you spaced and sized the pads correctly you should be able to use either one.  And the first set of pads could be elongated to fit the D sized Tantalum.  So really no difference but more versatile.

 

0805s because.......cheaper?  But such a PITA!  Brightness shouldn't be a concern as that'll be controlled with the resistor. I don't really care about this though. Just curious why you'd want to use 0805s.

 

But about the Tantalums. They are way too tall. Have you tried to use them yet. On most cars these will either not fit or be visible. Unless you find a tantalum that is flatter, this is a waste of time.

 

4 minutes ago, chadbag said:

 

The rectifier is not necessary if you are feeding it from a decoder.   It should be possible to make both of these optional on the board so that you can use the same board for various options and components.

 

Ok. I forgot you want to put decoders in cars for interior lights. That's reasonable then.

[gavino200]

2 minutes ago, chadbag said:

 

Once we had a design we like I'll send off for a minimum size sample order (like 10 or 20) and we'll try them out.  If they wor we'll see what larger sized orders are and who wants some.

 

It would be much easier to just wire up a circuit so we know that the design works and the brightnes and duration are what we're looking for. If it passes the "breadboard test" then send off the design.

 

Basically the wild card or "unknown" is how many capacitors to use.

[chadbag]

1 minute ago, gavino200 said:

 

It would be much easier to just wire up a circuit so we know that the design works and the brightnes and duration are what we're looking for. If it passes the "breadboard test" then send off the design.

 

Basically the wild card or "unknown" is how many capacitors to use.

 

 

The board is being designed to let multiple sets of values be used.  You may use one set and I another.  Ie, maybe up to 10 caps and LEDs every 14mm or something like that and you choose what you want to put on.  So there will be no one-set of ultimate values.  The idea is to get the circuit path right, and then let each person experiment.  We can publish what values we find useful so others can use those.

 

About the tantalum.  If it can be done by merely making the first capacitor position have extra long pads that will fit both then why not?  I want to use up whatever pieces I have left after I finish using my Dani-style LED strips up.  If I have extra pieces I'd rather use them than hassle with selling on eBay (not worth the time or effort for the small amount of dollars) and if it is just a matter of making the first cap position slightly different sized then make it more versatile.

[chadbag]

On a different note.

16 minutes ago, gavino200 said:

 

My "Dani style" strips with 1206 LEDs have an LED every 17mm

 

TORMs use 0805s or smaller and are every 11mm.

 

 

Maybe split the difference at 14mm or something.

 

The Tomix diffusers were approx 9.5mm and the KATO ones are 13.5 mm approximately (17/32").  How wide are the TORM boards?

 

[chadbag]

On a different note.

 

I've been reading and many different sources say to put a small value resister on the  input of each LED when you have many LEDs in parallel.  Or maybe every 2 or something(?)

 

Do we want to try that?  It may be safer.

Edited March 2, 2019 by chadbag

[gavino200]

8 minutes ago, chadbag said:

 

 

The board is being designed to let multiple sets of values be used.  You may use one set and I another.  Ie, maybe up to 10 caps and LEDs every 14mm or something like that and you choose what you want to put on.  So there will be no one-set of ultimate values.  The idea is to get the circuit path right, and then let each person experiment.  We can publish what values we find useful so others can use those.

 

I'm guessing you're making a few long solder pads where people can squeeze in as many caps as they want. Sort of like a pair of rails or wires rather than distinct individual solder pads. Yeah, that would work. I like it.

 

8 minutes ago, chadbag said:

 

About the tantalum.  If it can be done by merely making the first capacitor position have extra long pads that will fit both then why not?  I want to use up whatever pieces I have left after I finish using my Dani-style LED strips up.  If I have extra pieces I'd rather use them than hassle with selling on eBay (not worth the time or effort for the small amount of dollars) and if it is just a matter of making the first cap position slightly different sized then make it more versatile.

 

So....one tant pad close to the end of the wagon where you think you can hide it. No biggy. I guess you can always ditch it, if push comes to shove in a struggle for real estate. But if it fit why not. 

[gavino200]

17 minutes ago, chadbag said:

 

Maybe split the difference at 14mm or something.

 

Sure. Are the capacitor rails fitting in between the LEDs? If so then more space is better. Brightness won't be a problem. You'll have to turn these things way don't to avoid being "blinded by the sun".

 

17 minutes ago, chadbag said:

 

The Tomix diffusers were approx 9.5mm and the KATO ones are 13.5 mm approximately (17/32").  How wide are the TORM boards?

 

 

TORM Boards are  12mm. But they have perforations that allow them to be narrowed down to 7mm except at the end where the half rectifiers are. 

 

Were you planning on having this thing lay at the Kato/Tomix level (top of the interior details/walls? Or adhesed to the underside of the roof as per the Dani method?

Edited March 2, 2019 by gavino200

[cteno4]

1206 are a lot easier to solder than 805s, the pads are bigger and easier to hold onto. Might try some tests on spacing and led numbers in some cars. Just solder up some 1206 along some buss wire at various spacing and numbers to play with. Same with resistors, use the 805 as the 603 can be hard to handle. If you are making a lot of these make it easy on yourself and also for those that may not be as nimble! 

 

Ceramics are tougher and lower profile. They can take spikes and also fail open, which won’t cause other issues with tripping dcc or melting other bits.

 

best to test the circuit well before lots of pcb work and torture test it some.

 

also I think the capacitor inrush limiting resistor can be smaller, might test it.

 

jeff

[gavino200]

19 minutes ago, chadbag said:

On a different note.

 

I've ben reading and many different sources say to put a small value resister on the  input of each LED when you have many LEDs in parallel.  Or maybe every 2 or something(?)

 

Do we want to try that?  It may be safer.

 

I wouldn't. I think that's overkill. It would be nice if this thing was quick and easy to set up. 

[chadbag]

2 minutes ago, gavino200 said:

 

TORM Boards are  12mm. But they have perforations that allow them to be narrowed down to 7mm except at the end where the half rectifiers are. 

 

Were you planning on having this thing lay at the Kato/Tomix level (top of the interior details/walls? Or adhesed to the underside of the roof as per the Dani method?

 

Probably adhesed to the underside of the body shell roof.  I'll make as narrow as possible.

 

I'd also like to use these in the longer european cars so want to make the last few LEDs on perforated sections that can be easily hacked off to shorten the boards.  Just wire a jumper across.

 

 

[chadbag]

Just now, gavino200 said:

 

I wouldn't. I think that's overkill. It would be nice if this thing was quick and easy to set up. 

 

All the sources say this is how you limit or eliminate the chance of a runaway led dying and leading to others dying through drawing too much current.