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Offline DaleSchultz  
#1 Posted : 29 April 2019 18:14:39(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
One of my plans is to install interior lighting in all my passenger coaches. I have tried some of the Märklin units such as the 73400 but I want something much better and way more economical so I am keen to hear from knowledgeable electronics folk on this topic.....

Due to the large number of coaches, I have decided I want to use track power. I am aware of the battery solutions and don't want to discuss that in this thread.

I plan on connecting the coaches together so that I do not have to have one pickup shoe per coach. This will reduce cost, drag and noise.
The connections between coaches could be permanent, or use some small plugs.

Here are my 'requirements and goals'

  • Use the typical off the shelf 12V (or 24V) LED strips that can be cut to length.
  • Use digital track current as power supply
  • Reduce the brightness of the LEDs
  • Not waste valuable digital track current
  • Be flicker free (At the Mhz level and short power drops)
  • Not have a large inrush of current when power is initially applied
  • Not generate unnecessary heat (some coaches have plastic rooves, and I don't want to waste the energy)
  • Electronics must be small enough to fit inside a coach or Gepäkwagen


I don't think I need to be able to switch them off digitally, but that would be a nice feature to save power in hidden staging yards. An input contact that could be connected to a cheap decoder to switch it will be a very nice feature. (The decoder would only indicate the switching, not supply the power.)

I know how to rectify and smooth the digital current.
I know how to add a capacitor to prevent flicker.
I think I can find a circuit to reduce inrush.

What I would like to solve is how to reduce the brightness of the LEDs for better visual and less power consumption, without generating heat through a resistor load. I think that a pulse width dimmer would be ideal, allowing the LEDs to run at 12V but not all the time, thus avoiding waste through heat.

I am aware of small buck converters that convert DC voltage to lower voltages with good efficiency.
I am wondering what happens if one does not rectify the input current to a buck converter.
I am wondering if adjusting the output voltage of a buck converter instead of using PWD is a good approach.

I am open to designing a small circuit board and having them made, and then adding the components myself. My plan is to add a pickup shoe to a coach containing my circuit board, then take the output of the board through all the coaches in the rake to provide power to their LED strips.

Obviously, such a circuit board will have some upper limit of how many LEDs is will be able to drive. That limit will simply determine the length of the rake powered by one board. If I have to light a train longer than that, I add another pickup shoe and board. The 12V LEDs at full brightness consume about 80mA per 20cm.

Should I look at creating a PWD circuit using something like a 555 timer?
or would a rectifier + buck converter be a better approach? (and more available)

Would 24V LED strips be better than 12V? They would require less reduction in voltage from the rectified track current (25V?) and also perhaps require less current?
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline rbw993  
#2 Posted : 29 April 2019 18:29:08(UTC)
rbw993

United States   
Joined: 19/08/2008(UTC)
Posts: 680
Have you looked at this Dale? https://www.marklin-users.net/fo...n-Marklin-passenger-Cars

I have done about 40 cars using this method.

Regards,
Roger
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Offline DaleSchultz  
#3 Posted : 29 April 2019 18:58:47(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: rbw993 Go to Quoted Post
Have you looked at this Dale? https://www.marklin-users.net/fo...n-Marklin-passenger-Cars

I have done about 40 cars using this method.

Regards,
Roger


ah yes, thanks, I do recall that thread, and I had forgotten that great tick of running the current through two strips. We could run two cars at once so each car has one strip. I will read through it again.

Do you have all 40 on the layout when you power up? If so do you have inrush issues?
How hot do the resistors get?
Are they overly bright?

I can separate the circuitry from the pickup shoe, so small simple circuits in each (or every other) car could all be fed from a single pickup.
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline rbw993  
#4 Posted : 29 April 2019 20:23:01(UTC)
rbw993

United States   
Joined: 19/08/2008(UTC)
Posts: 680
Dale
No problem at power up with the thirty lit cars on the layout at this time, but the layout is split into three sections with boosters so no one section gets all the load. I haven't noticed any resistor heating, no car body melting or smell. I generally use 2 of the resistors in parallel to reduce the brightness. All cars have a ground spring on one truck but only every three or four have a slider.

Roger
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Offline mmervine  
#5 Posted : 29 April 2019 22:14:34(UTC)
mmervine

United States   
Joined: 30/01/2006(UTC)
Posts: 1,807
Location: Keene, NH
I have used many, many of these. Come w/bridge rectifier, rheostat, and capacitors. Hard to build your own at these prices.

https://www.ebay.com/itm...311b9:g:wLUAAOSwaeRbOQcX
Märklin C-track, Digital, ECoS, multi-era French & Swiss
http://www.ete-ene.org/m...mervines-layout-gallery/
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Offline DaleSchultz  
#6 Posted : 30 April 2019 04:08:13(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
came across a blog article that describes using a DC converter to ensure that the energy stored in a capacitor can be maximized:

https://model-railroad-hobbyist.com/node/22380

This means less flicker!

I had not thought of that advantage!

Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline rbw993  
#7 Posted : 30 April 2019 13:31:57(UTC)
rbw993

United States   
Joined: 19/08/2008(UTC)
Posts: 680
Are those $25 each Mark or am I reading it wrong? The topic in the link I posted includes a capacitor to reduce flicker for about a tenth the cost.
Thanks,
Roger
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Offline DaleSchultz  
#8 Posted : 30 April 2019 14:05:50(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Mark's link is for 5, so $6 each. Pricey.
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline Ross  
#9 Posted : 02 May 2019 01:41:26(UTC)
Ross

Australia   
Joined: 25/09/2006(UTC)
Posts: 750
Location: Sydney, NSW
Hi Dale/All,

My comment is to keep it simple and keep away from LED light strips. Have a look at some of my LED lighting projects under my Tips section on my Web page for ideas.

Ross
Offline DaleSchultz  
#10 Posted : 02 May 2019 16:09:53(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Hi Ross,

I looked through a bunch of your tips and see that you tend to make your own PCBs for the lighting, but I did not see any mention as to why you think your home made strips differ from the LED strips which are so readily available.

Do you think the commercial one have the LEDs too close?
Do you find their resister level is not what you want?

As far as I see it the LED strips one can buy are simply strings of three LEDs with their own resistor.
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline rbw993  
#11 Posted : 02 May 2019 16:16:10(UTC)
rbw993

United States   
Joined: 19/08/2008(UTC)
Posts: 680
I have had no issues with the strips except the adhesive on the back could be stronger. A little contact adhesive fixes that. I have used two spools so far and have had no failures.
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Offline DaleSchultz  
#12 Posted : 02 May 2019 18:26:36(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
yes, the adhesive is fake 3M and I disregard it, and do my own fastening.
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline Ross  
#13 Posted : 02 May 2019 23:45:46(UTC)
Ross

Australia   
Joined: 25/09/2006(UTC)
Posts: 750
Location: Sydney, NSW
Hi Dale/All,

Originally Posted by: DaleSchultz Go to Quoted Post
Hi Ross,

I looked through a bunch of your tips and see that you tend to make your own PCBs for the lighting, but I did not see any mention as to why you think your home made strips differ from the LED strips which are so readily available.

Do you think the commercial one have the LEDs too close?
Yes the LED's are too close

Do you find their resister level is not what you want?
The light strips are designed for 12Vdc but in the train the Voltage is 15Vdc after the bridge rectifier so resistor values must be higher to keep the LED current on the low side of the LED spec

Interior colours will affect the light balance. Most people myself included have pointed the LED's down but this will cause hot spots so where possible I have started to point the LED's up and the light is softened by reflecting the light off white paper to even the light through out the coach.

Not all coaches are the same so you have to adapt the lighting technique to suit. It is also good practice to be able to switch the lights off when the train isn't running as this prevents a high power drain on your track power. Removing bulb lighting from coaches and engines reduces the high current required and also removes the heat factor.

The only place I have used LED light strips is for my station platforms and to control the light intensity I input 9Vdc instead of 12Vdc


As far as I see it the LED strips one can buy are simply strings of three LEDs with their own resistor.


Ross
Offline DaleSchultz  
#14 Posted : 03 May 2019 03:40:46(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: Ross Go to Quoted Post
The light strips are designed for 12Vdc but in the train the Voltage is 15Vdc after the bridge rectifier so resistor values must be higher to keep the LED current on the low side of the LED spec


I would have expected more than 15V, in fact I am expecting around 25V (18 * 1.4) after rectification and smoothing. Still need to measure that. 15V would be nicer of course.

Originally Posted by: Ross Go to Quoted Post

Interior colours will affect the light balance. Most people myself included have pointed the LED's down but this will cause hot spots so where possible I have started to point the LED's up and the light is softened by reflecting the light off white paper to even the light through out the coach.


I like that idea, especially if the light does not shine through a plastic roof. In which case some black tape and white paper will be needed. On the other hand, when the LEDs are closer together, I expect get less of a 'hot spot' difference.

Originally Posted by: Ross Go to Quoted Post
It is also good practice to be able to switch the lights off when the train isn't running as this prevents a high power drain on your track power.


Yes, this is one of my 'nice to have goals' and my software is prepared for this already, I would switch the coach lights off in hidden areas as I do already for certain other functions. (Rather than when not running.)

Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline Ross  
#15 Posted : 03 May 2019 08:48:45(UTC)
Ross

Australia   
Joined: 25/09/2006(UTC)
Posts: 750
Location: Sydney, NSW
Hi Dale/All,

The 15Vdc is obtained when I use a 6080 decoder with a bridge rectifier as I have shown in my circuit diagrams for the lighting articles.

Originally Posted by: DaleSchultz Go to Quoted Post
I would have expected more than 15V, in fact I am expecting around 25V (18 * 1.4) after rectification and smoothing. Still need to measure that. 15V would be nicer of course.




Ross
Offline tiono  
#16 Posted : 05 May 2019 14:39:37(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
LED strip is good. The only drawback is: low efficiency of power utilization.
I have tested in Marklin 27cm coach.
Within that length, there are 21 LED chips (my LED strip use 0305 LED). If connected to 12V supply, those 21 LEDs draw around 200mA of current, and way too bright to be put in a HO-scale coach. I reduced the voltage until it reached suitable brightness, measured around 8.5V 20mA.
The measured voltage after bridge rectifier is around 18V, thus I need a resistor to drop the voltage. The resistor value is calculated by dividing drop voltage of 9.5V and the 20mA current, which come around 475 ohm.
The result is good; simple, easy to install, the coach is evenly lit due to dense LED chips. The LED strip itself use around 0.17 watt, but the additional resistor (the 475 ohm) dissipate 0.19 watt. Total power usage of the coach is 0.36 watt, where more than half is wasted on the resistor. Well, even if half of the energy is wasted, I'm sure its power usage is still lower than those Marklin interior lighting using conventional bulb.
thanks 1 user liked this useful post by tiono
Offline DaleSchultz  
#17 Posted : 05 May 2019 15:07:26(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: tiono Go to Quoted Post
LED strip is good. The only drawback is: low efficiency of power utilization.
I have tested in Marklin 27cm coach.
Within that length, there are 21 LED chips (my LED strip use 0305 LED). If connected to 12V supply, those 21 LEDs draw around 200mA of current, and way too bright to be put in a HO-scale coach. I reduced the voltage until it reached suitable brightness, measured around 8.5V 20mA.
The measured voltage after bridge rectifier is around 18V, thus I need a resistor to drop the voltage. The resistor value is calculated by dividing drop voltage of 9.5V and the 20mA current, which come around 475 ohm.
The result is good; simple, easy to install, the coach is evenly lit due to dense LED chips. The LED strip itself use around 0.17 watt, but the additional resistor (the 475 ohm) dissipate 0.19 watt. Total power usage of the coach is 0.36 watt, where more than half is wasted on the resistor. Well, even if half of the energy is wasted, I'm sure its power usage is still lower than those Marklin interior lighting using conventional bulb.


This is what I suspect, and why I think the solution is not to use a resistor but a pulse width dimming approach, ideally as part of the converter from 18 to 12V. In other words a small module that takes the digital track current, rectifies it, buffers it and puts out a 12V PWD output. I think that should get rid of all the waste.


Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline tiono  
#18 Posted : 05 May 2019 16:25:17(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: DaleSchultz Go to Quoted Post
Originally Posted by: tiono Go to Quoted Post
LED strip is good. The only drawback is: low efficiency of power utilization.
I have tested in Marklin 27cm coach.
Within that length, there are 21 LED chips (my LED strip use 0305 LED). If connected to 12V supply, those 21 LEDs draw around 200mA of current, and way too bright to be put in a HO-scale coach. I reduced the voltage until it reached suitable brightness, measured around 8.5V 20mA.
The measured voltage after bridge rectifier is around 18V, thus I need a resistor to drop the voltage. The resistor value is calculated by dividing drop voltage of 9.5V and the 20mA current, which come around 475 ohm.
The result is good; simple, easy to install, the coach is evenly lit due to dense LED chips. The LED strip itself use around 0.17 watt, but the additional resistor (the 475 ohm) dissipate 0.19 watt. Total power usage of the coach is 0.36 watt, where more than half is wasted on the resistor. Well, even if half of the energy is wasted, I'm sure its power usage is still lower than those Marklin interior lighting using conventional bulb.


This is what I suspect, and why I think the solution is not to use a resistor but a pulse width dimming approach, ideally as part of the converter from 18 to 12V. In other words a small module that takes the digital track current, rectifies it, buffers it and puts out a 12V PWD output. I think that should get rid of all the waste.


You're right. By using PWM regulator, the wasted power will be reduced. I have tested using a small low-cost PWM which can fit into the coach (see photo below). The regulator's efficiency is 85%. The input current drop to around 11mA although the LED strip is still drawing 20mA at 8.5V
This is great if you have a lot of coaches on the layout.



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Offline kiwiAlan  
#19 Posted : 05 May 2019 19:25:43(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 5,397
Location: ENGLAND, Didcot
Those LED strips usually seem to have three LEDS in series with a resistor that is sized for 12V operation. The power 'rails' run all the way down the strip, positive one side and negative the other, but only every third LED actually makes a connection to it. This is so that LED strings can be cut to length without the end user having to do anything special other than use a pair of scissors.

So by removing the resistor on one set of three LEDs and cutting the track to the power rail on the adjacent set of three LEDs and connecting the disconnected LED to where the resistor used to be you should get a much more efficient use of the current. At digital supply voltages you may be able to connect three sets of LEDs, i.e. nine LEDs in total, in a string and still have it work. To adjust the brightness you could even remove the resistor from the strip and then you can fine tune the resistor value externally if it isn't bright enough, although that would surprise me as the white LEDs are very bright even at very low currents.

Offline DaleSchultz  
#20 Posted : 05 May 2019 21:05:30(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: tiono Go to Quoted Post

You're right. By using PWM regulator, the wasted power will be reduced. I have tested using a small low-cost PWM which can fit into the coach (see photo below). The regulator's efficiency is 85%. The input current drop to around 11mA although the LED strip is still drawing 20mA at 8.5V
This is great if you have a lot of coaches on the layout.


That sounds good, what PWM controller is that ?
I do have a lot of coaches and I would like to optimise what I install.
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline DaleSchultz  
#21 Posted : 05 May 2019 22:21:20(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Further confirmation that a switching converter is the direction to go...
see https://www.instructables.com/id/Poormans-Buck/
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline mrmarklin  
#22 Posted : 06 May 2019 01:05:17(UTC)
mrmarklin

United States   
Joined: 27/10/2004(UTC)
Posts: 823
Location: Burney, CA
Originally Posted by: DaleSchultz Go to Quoted Post
One of my plans is to install interior lighting in all my passenger coaches. I have tried some of the Märklin units such as the 73400 but I want something much better and way more economical so I am keen to hear from knowledgeable electronics folk on this topic.....

Due to the large number of coaches, I have decided I want to use track power. I am aware of the battery solutions and don't want to discuss that in this thread.

I plan on connecting the coaches together so that I do not have to have one pickup shoe per coach. This will reduce cost, drag and noise.
The connections between coaches could be permanent, or use some small plugs.

Here are my 'requirements and goals'

  • Use the typical off the shelf 12V (or 24V) LED strips that can be cut to length.
  • Use digital track current as power supply
  • Reduce the brightness of the LEDs
  • Not waste valuable digital track current
  • Be flicker free (At the Mhz level and short power drops)
  • Not have a large inrush of current when power is initially applied
  • Not generate unnecessary heat (some coaches have plastic rooves, and I don't want to waste the energy)
  • Electronics must be small enough to fit inside a coach or Gepäkwagen


I don't think I need to be able to switch them off digitally, but that would be a nice feature to save power in hidden staging yards. An input contact that could be connected to a cheap decoder to switch it will be a very nice feature. (The decoder would only indicate the switching, not supply the power.)

I know how to rectify and smooth the digital current.
I know how to add a capacitor to prevent flicker.
I think I can find a circuit to reduce inrush.

What I would like to solve is how to reduce the brightness of the LEDs for better visual and less power consumption, without generating heat through a resistor load. I think that a pulse width dimmer would be ideal, allowing the LEDs to run at 12V but not all the time, thus avoiding waste through heat.

I am aware of small buck converters that convert DC voltage to lower voltages with good efficiency.
I am wondering what happens if one does not rectify the input current to a buck converter.
I am wondering if adjusting the output voltage of a buck converter instead of using PWD is a good approach.

I am open to designing a small circuit board and having them made, and then adding the components myself. My plan is to add a pickup shoe to a coach containing my circuit board, then take the output of the board through all the coaches in the rake to provide power to their LED strips.

Obviously, such a circuit board will have some upper limit of how many LEDs is will be able to drive. That limit will simply determine the length of the rake powered by one board. If I have to light a train longer than that, I add another pickup shoe and board. The 12V LEDs at full brightness consume about 80mA per 20cm.

Should I look at creating a PWD circuit using something like a 555 timer?
or would a rectifier + buck converter be a better approach? (and more available)

Would 24V LED strips be better than 12V? They would require less reduction in voltage from the rectified track current (25V?) and also perhaps require less current?


The product you are looking for is made by kuehn-digital in Germany. One can install a cheap capacitor in conjunction with the LED strip and achieve all your goals. www.kuehn-digital.de.

Cost is about €20.

I buy mine from Matschke Modellbahn.
From the People's Republik of Kalifornia
Offline tiono  
#23 Posted : 06 May 2019 02:06:50(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: DaleSchultz Go to Quoted Post
Originally Posted by: tiono Go to Quoted Post

You're right. By using PWM regulator, the wasted power will be reduced. I have tested using a small low-cost PWM which can fit into the coach (see photo below). The regulator's efficiency is 85%. The input current drop to around 11mA although the LED strip is still drawing 20mA at 8.5V
This is great if you have a lot of coaches on the layout.


That sounds good, what PWM controller is that ?
I do have a lot of coaches and I would like to optimise what I install.


The PWM regulator can be easily purchased from eBay. Search keyword: "mini DC regulator". Look for the one which using PWM chip MP2307. I found that this chip is small and reliable to work on intermittent rail supply (dirty track), but its max input voltage is just 23 volt, therefore is not suitable for Marklin analog with high reversing voltage. I bought it from eBay, 10 pieces US$7 (less than $1 per piece)

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Offline DaleSchultz  
#24 Posted : 06 May 2019 02:34:42(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: tiono Go to Quoted Post


The PWM regulator can be easily purchased from eBay. Search keyword: "mini DC regulator". Look for the one which using PWM chip MP2307. I found that this chip is small and reliable to work on intermittent rail supply (dirty track), but its max input voltage is just 23 volt, therefore is not suitable for Marklin analog with high reversing voltage. I bought it from eBay, 10 pieces US$7 (less than $1 per piece)



Thanks I have ordered some. 36c each!
Have you tried adding a capacitor to look after short power losses? If so, do you have a recommendation?
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline DaleSchultz  
#25 Posted : 06 May 2019 02:40:32(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: mrmarklin Go to Quoted Post

Cost is about €20.


Hmm yes well... at least it does include a decoder at that price...

But a single function decoder can be had for less that $15 and the rest is less than a dollar...


Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline mrmarklin  
#26 Posted : 06 May 2019 02:49:56(UTC)
mrmarklin

United States   
Joined: 27/10/2004(UTC)
Posts: 823
Location: Burney, CA
Originally Posted by: DaleSchultz Go to Quoted Post
Originally Posted by: mrmarklin Go to Quoted Post

Cost is about €20.


Hmm yes well... at least it does include a decoder at that price...

But a single function decoder can be had for less that $15 and the rest is less than a dollar...




This is not a single function decoder. It has ca. 69 CVs. And can drive other lights etc. such as taillights.

I find it hard to believe you can duplicate all the functions of this unit for the price.

Plus the value of your time. Blink
From the People's Republik of Kalifornia
Offline tiono  
#27 Posted : 06 May 2019 04:25:33(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: DaleSchultz Go to Quoted Post


Thanks I have ordered some. 36c each!
Have you tried adding a capacitor to look after short power losses? If so, do you have a recommendation?


I do add a capacitor at the output of bridge rectifier (the input of PWM regulator).
Capacitor value: 47uF 25V Panasonic, from Digikey.com at 27 cents each. This capacitor size is just around 7mm x 6mm, small enough to fit into the coach's corner.
Theoretically, bigger value is better, but the size will be larger too, and if you have many coaches on the layout, then the combined in-rush current during power-up may trip the controller.
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Offline mario54i  
#28 Posted : 06 May 2019 10:51:38(UTC)
mario54i

Italy   
Joined: 28/03/2007(UTC)
Posts: 211
Location: Torino,
The device you are referring to is a step-down or buck converter, that relies on charging and discharging an inductor in a way similar to PWM.
Calling it PWM regulator is misleading, a simple PWM that turns on and off power periodically is not saving power.
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Offline tiono  
#29 Posted : 06 May 2019 11:54:12(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: mario54i Go to Quoted Post
The device you are referring to is a step-down or buck converter, that relies on charging and discharging an inductor in a way similar to PWM.
Calling it PWM regulator is misleading, a simple PWM that turns on and off power periodically is not saving power.


"Buck converter" is the term widely used by common public.
Technically, this device is called "switching regulator". Since the output voltage (or current) has to be regulated, therefore it need a method to modulate the switching. Common switching modulation method are: PWM and PFM (see the basic here: https://micro.rohm.com/en/techweb/knowledge/dcdc/s-dcdc/02-s-dcdc/90 )
My device is using PWM method (switching frequency is fixed at 340 KHz), therefore it is simply called "PWM regulator" (to differentiate against other type).
Most of switching power supply, use PWM modulation with fixed switching frequency so that the inductor/transformer can be optimized into single frequency.
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Offline David Dewar  
#30 Posted : 06 May 2019 12:39:36(UTC)
David Dewar

Scotland   
Joined: 01/02/2004(UTC)
Posts: 6,982
Location: Scotland
I gave up on anything that takes current from a slider as trying to avoid any flicker was almost impossible and at best costly.
Look forward to hear how Dale ends up doing this.
Take care I like Marklin and will defend the worlds greatest model rail manufacturer.
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Offline DaleSchultz  
#31 Posted : 06 May 2019 14:39:25(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: mrmarklin Go to Quoted Post

This is not a single function decoder. It has ca. 69 CVs. And can drive other lights etc. such as taillights.

I find it hard to believe you can duplicate all the functions of this unit for the price.

Plus the value of your time. Blink


well $15 decoders can have 6 functions, but still irrelevant if I only need one function.

PWM regulator: 36c
capacitor: 27c
LED strip: 50c
some wire: 5c ?





Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline DaleSchultz  
#32 Posted : 06 May 2019 14:42:34(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: tiono Go to Quoted Post

I do add a capacitor at the output of bridge rectifier (the input of PWM regulator).
Capacitor value: 47uF 25V Panasonic, from Digikey.com at 27 cents each. This capacitor size is just around 7mm x 6mm, small enough to fit into the coach's corner.
Theoretically, bigger value is better, but the size will be larger too, and if you have many coaches on the layout, then the combined in-rush current during power-up may trip the controller.


Great, I will start there. I might also look at adding a resistor to limit inrush.

Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline LongHairedDavid  
#33 Posted : 06 May 2019 16:58:54(UTC)
LongHairedDavid


Joined: 04/01/2019(UTC)
Posts: 344
Location: England, Ipswich
Originally Posted by: DaleSchultz Go to Quoted Post
Originally Posted by: tiono Go to Quoted Post

I do add a capacitor at the output of bridge rectifier (the input of PWM regulator).
Capacitor value: 47uF 25V Panasonic, from Digikey.com at 27 cents each. This capacitor size is just around 7mm x 6mm, small enough to fit into the coach's corner.
Theoretically, bigger value is better, but the size will be larger too, and if you have many coaches on the layout, then the combined in-rush current during power-up may trip the controller.


Great, I will start there. I might also look at adding a resistor to limit inrush.



I use Layouts4U units that incorporate a reed switch. At £6 per unit, they are very economical. Each coach has a battery and you turn the lights on or off with a magnet. The batteries are very cheap on Amazon - 10 packs of CR2032 are just £4.99.



Long Haired David
AKA David Pennington
A mystified Maerklin Newbie
Offline tiono  
#34 Posted : 06 May 2019 17:45:04(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: David Dewar Go to Quoted Post
I gave up on anything that takes current from a slider as trying to avoid any flicker was almost impossible and at best costly.
Look forward to hear how Dale ends up doing this.


Based on my experience, the most effective method to reduce flicker is; install at least two sliders in one consist (at each end of the consist) and connect all of the coaches by two-pole micro connectors (or two-pole current conducting coupler). Longer consist may use three sliders or more.



Offline David Dewar  
#35 Posted : 06 May 2019 20:33:23(UTC)
David Dewar

Scotland   
Joined: 01/02/2004(UTC)
Posts: 6,982
Location: Scotland
Originally Posted by: tiono Go to Quoted Post
Originally Posted by: David Dewar Go to Quoted Post
I gave up on anything that takes current from a slider as trying to avoid any flicker was almost impossible and at best costly.
Look forward to hear how Dale ends up doing this.


Based on my experience, the most effective method to reduce flicker is; install at least two sliders in one consist (at each end of the consist) and connect all of the coaches by two-pole micro connectors (or two-pole current conducting coupler). Longer consist may use three sliders or more.





Have tried that but I am not keen on sliders as they add to unwanted noise and some coaches ...mainly Brawa ... have difficulty at turnouts. I now use the method that Dale does not want and saves cash and flicker. Interested in this thread though.
Take care I like Marklin and will defend the worlds greatest model rail manufacturer.
Offline Minok  
#36 Posted : 06 May 2019 20:37:52(UTC)
Minok

United States   
Joined: 15/10/2006(UTC)
Posts: 2,182
Location: Washington, Pacific Northwest
Originally Posted by: tiono Go to Quoted Post
Originally Posted by: DaleSchultz Go to Quoted Post


Thanks I have ordered some. 36c each!
Have you tried adding a capacitor to look after short power losses? If so, do you have a recommendation?


I do add a capacitor at the output of bridge rectifier (the input of PWM regulator).
Capacitor value: 47uF 25V Panasonic, from Digikey.com at 27 cents each. This capacitor size is just around 7mm x 6mm, small enough to fit into the coach's corner.
Theoretically, bigger value is better, but the size will be larger too, and if you have many coaches on the layout, then the combined in-rush current during power-up may trip the controller.


Thats the reason the a capacitor buffered circuit should have a resistor/diode combo feeding that capacitor, to force the charging current to go through the resistor, thus the resistor limits the charge rate to control the layout wide inflow at power up.
Toys of tin and wood rule!
---
My Layout Thread on marklin-users.net: InterCity 1-3-4
My YouTube Channel: https://www.youtube.com/user/Minok1217/
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Offline DaleSchultz  
#37 Posted : 06 May 2019 23:21:20(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: tiono Go to Quoted Post


Based on my experience, the most effective method to reduce flicker is; install at least two sliders in one consist (at each end of the consist) and connect all of the coaches by two-pole micro connectors (or two-pole current conducting coupler). Longer consist may use three sliders or more.


Note: that this is fine if you do not have boosters. If you have more than one power district, this will likely connect the center rail of two districts when the train runs from one to the other.

I would first look at additional capacitors, to handle short power interruptions before adding a second slider.

Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
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Offline tiono  
#38 Posted : 07 May 2019 04:31:07(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: DaleSchultz Go to Quoted Post

Note: that this is fine if you do not have boosters. If you have more than one power district, this will likely connect the center rail of two districts when the train runs from one to the other.
I would first look at additional capacitors, to handle short power interruptions before adding a second slider.


If your layout does not allow the usage of multiple sliders, then probably you would like to consider the idea of using super-capacitor inside baggage coach.
The drawback of this concept; must use a baggage coach within the consist. And must wait a few minute during power up, to charge the super-capacitor.
With a 45F/5.6V super-cap, if there are 10 coaches and each drawing 20mA/5V (each LED strip takes around 15mA at 8.4V), then you will have almost two minutes of back-up power. More than enough to be flicker free.
Diagram below:
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Offline applor  
#39 Posted : 07 May 2019 07:28:01(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,567
Location: Brisbane, Queensland
I replaced the old Marklin slider with hole on my Rheingold F-train set with a Brawa slider. It actually removed 95% of flicker - it's pretty rock solid now.

Bad flickering probably indicates poor slider contact, likely between the leaf spring part and the slider rather than the slider to the studs.
modelling 1954 Germany (era IIIa)
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Offline DaleSchultz  
#40 Posted : 07 May 2019 17:23:56(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: tiono Go to Quoted Post

If your layout does not allow the usage of multiple sliders, then probably you would like to consider the idea of using super-capacitor inside baggage coach.
The drawback of this concept; must use a baggage coach within the consist. And must wait a few minute during power up, to charge the super-capacitor.
With a 45F/5.6V super-cap, if there are 10 coaches and each drawing 20mA/5V (each LED strip takes around 15mA at 8.4V), then you will have almost two minutes of back-up power. More than enough to be flicker free.
Diagram below:


Excellent illustrations!

It appears that the super cap needs to be a lower voltage, requiring two voltages changes. If one is using the ample space in the baggage car why not a bank of paper caps? I don't mind the power up time.

I am thinking of using header pins (or pairs) for connecting wires between coaches, or have you seen a better solution that is as economical?
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline ktsolias  
#41 Posted : 07 May 2019 17:36:28(UTC)
ktsolias

Greece   
Joined: 01/05/2016(UTC)
Posts: 511
Location: Athens
Originally Posted by: tiono Go to Quoted Post
Originally Posted by: DaleSchultz Go to Quoted Post

Note: that this is fine if you do not have boosters. If you have more than one power district, this will likely connect the center rail of two districts when the train runs from one to the other.
I would first look at additional capacitors, to handle short power interruptions before adding a second slider.


If your layout does not allow the usage of multiple sliders, then probably you would like to consider the idea of using super-capacitor inside baggage coach.
The drawback of this concept; must use a baggage coach within the consist. And must wait a few minute during power up, to charge the super-capacitor.
With a 45F/5.6V super-cap, if there are 10 coaches and each drawing 20mA/5V (each LED strip takes around 15mA at 8.4V), then you will have almost two minutes of back-up power. More than enough to be flicker free.
Diagram below:


This circuit is not working because you mix rectified DC current and current from the rails

Costas
Offline DaleSchultz  
#42 Posted : 07 May 2019 17:41:42(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
Originally Posted by: ktsolias Go to Quoted Post

This circuit is not working because you mix rectified DC current and current from the rails

I don't think it does. It just uses the common ground. The red line is from the pickup.

Any LED in any train powered from the digital track signal is doing the same.
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline ktsolias  
#43 Posted : 07 May 2019 18:47:46(UTC)
ktsolias

Greece   
Joined: 01/05/2016(UTC)
Posts: 511
Location: Athens
Originally Posted by: DaleSchultz Go to Quoted Post
Originally Posted by: ktsolias Go to Quoted Post

This circuit is not working because you mix rectified DC current and current from the rails

I don't think it does. It just uses the common ground. The red line is from the pickup.

Any LED in any train powered from the digital track signal is doing the same.


No
It is like to use the ground (brown) instead the U+ 18 (Orange) in a loco light

Costas
Offline Minok  
#44 Posted : 07 May 2019 20:04:17(UTC)
Minok

United States   
Joined: 15/10/2006(UTC)
Posts: 2,182
Location: Washington, Pacific Northwest
Originally Posted by: ktsolias Go to Quoted Post
Originally Posted by: DaleSchultz Go to Quoted Post
Originally Posted by: ktsolias Go to Quoted Post

This circuit is not working because you mix rectified DC current and current from the rails

I don't think it does. It just uses the common ground. The red line is from the pickup.

Any LED in any train powered from the digital track signal is doing the same.


No
It is like to use the ground (brown) instead the U+ 18 (Orange) in a loco light

Costas


That is a decoder issue, and GND (BR) is different from the power signal from U18 (OR), which is the 'motor output' from the decoder. You should not use the motor power output of a decoder to drive a light, that is true, and instead use the AUX outputs and the AUX-Return (BLU) instead of brown, but that is due to the way the switching occurs in the decoder, I believe.
Toys of tin and wood rule!
---
My Layout Thread on marklin-users.net: InterCity 1-3-4
My YouTube Channel: https://www.youtube.com/user/Minok1217/
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Offline tiono  
#45 Posted : 08 May 2019 03:14:24(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: ktsolias Go to Quoted Post
Originally Posted by: tiono Go to Quoted Post



This circuit is not working because you mix rectified DC current and current from the rails

Costas


Could you explain why it does not work?
Please note: the rectifier is not a bridge, but only half wave. See the diagram below:
The reason of using single diode (half wave rectifier) is to allow the usage of 2-pole connector. If using bridge rectifier, then yes, the ground can not be mixed with the rail, and that means; must use 3-pole connector.



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Offline tiono  
#46 Posted : 08 May 2019 03:33:27(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: DaleSchultz Go to Quoted Post

It appears that the super cap needs to be a lower voltage, requiring two voltages changes. If one is using the ample space in the baggage car why not a bank of paper caps? I don't mind the power up time.

I am thinking of using header pins (or pairs) for connecting wires between coaches, or have you seen a better solution that is as economical?


Common electrolytic capacitor bank can be used, but the capacity will not be as high as super-cap at the same physical size. Of course, capacitor bank of total 10000uF can be put inside baggage coach, and that's enough to eliminate flicker.
As super-cap has very high capacity, therefore giving the possibility of running a wire to the locomotive's decoder as power back up. (may need additional voltage step-up)

The option of 2-pole (or more) connector between coaches are:
- Micro connector (search on eBay using keyword: "mini steckerset 2 polig" )
- Roco 4-pole connecting coupler, item no 40345

Offline DaleSchultz  
#47 Posted : 08 May 2019 03:36:15(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
if we step back from the double conversion and power cap and go back to the simpler:

Center rail pickup -> Bridge rectifier -> DC-DC regulator -> Cap -> LED strip

Can the ground of the LED strip go to the common rail ground?
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline tiono  
#48 Posted : 08 May 2019 03:56:57(UTC)
tiono

United States   
Joined: 09/02/2010(UTC)
Posts: 234
Originally Posted by: DaleSchultz Go to Quoted Post
if we step back from the double conversion and power cap and go back to the simpler:

Center rail pickup -> Bridge rectifier -> DC-DC regulator -> Cap -> LED strip

Can the ground of the LED strip go to the common rail ground?


As long as there is a bridge rectifier, then the DC ground (output of the bridge rectifier, or the LED strip's ground) can not go to common rail.
But half wave rectifier is different; it use the same ground as the AC source.

rectifier
Offline DaleSchultz  
#49 Posted : 08 May 2019 04:31:57(UTC)
DaleSchultz

United States   
Joined: 10/02/2006(UTC)
Posts: 3,511
thanks again, I never knew that.
I had built full bridge rectified circuits that use a separate 16VAC supply and sharing the same ground, but of course that is NOT using digital power from the rails.

So:

Pickup shoe - half wave rectifier -> capacitor -> DC-DC regulator -> LED strip(s) -> rails
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline Minok  
#50 Posted : 08 May 2019 21:11:46(UTC)
Minok

United States   
Joined: 15/10/2006(UTC)
Posts: 2,182
Location: Washington, Pacific Northwest
So are we talking about a purely AC sinusoidal driven system here, where the mains is stepped down to a train-level AC signal? Otherwise the presence of the transformer and where its tapped doesn't matter.

With a full-wave bridge rectifier, yes where the slider is one pole, and the rails is the other pole, the output of that is a +ve power signal and the rectified ground, so that produces a ground/return signal inside the post-rectifier space. But that would work just fine. Whichever rectifier circuit one uses it has to be wired up correctly. Using a full wave bridge gets you more of the power signal to work with, so you need a smaller capacitor for the same smoothing, so why not use the full-wave bridge solution?

FWBRect.png

Everything attached to the right side +V/GND side is a complete circuit just inside the wagon/coach/car, without contact to the slider or rails.
Toys of tin and wood rule!
---
My Layout Thread on marklin-users.net: InterCity 1-3-4
My YouTube Channel: https://www.youtube.com/user/Minok1217/
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