Adding capacitance to Kato passenger car lighting kits

[milw156]

Has anyone wired in capacitors to the Car lighting kits(V2)? I was given some a while back, but the flickering is driving me nuts.

[wvgca]

are there already small caps in there ?? or nothing ??

[peteski]

I assume you mean the "rev 2" version of the lighting kit (not the original LED version).  I think that might be difficult due to the way the PC board is laid out.  I would have to revisit this circuit to refresh my memory.  I do recall it uses a constant current diode (not a typical resistor) to limit the current passing through the LED.

Keeping the car wheels (and the track of course) very clean works pretty well in getting rid of the flicker.

[carlso]

I post this with some reservation as I did not do this work nor do  I have any idea how it is wired, or size of caps or if this is even the lighting unit your asking about.

At any rate here is an image of a KATO tavern car. Seems to work well :



I know that helps a great deal.

[milw156]

Very interesting, DCC???

[peteski]

I whipped up something workable on my workbench today.  Will write it up and post it as the time allows.  The PC board new design is a bit challenging.

[milw156]

Awesome! 😊

[randgust]

DC, DCC, or both?    I've got a drumhead off of the El Cap cars that could use some help to stop the flicker.

[peteski]

DC, DCC, or both?    I've got a drumhead off of the El Cap cars that could use some help to stop the flicker.

Yes, that type of circuit works on DCC and DC, but unless you are running your models at full throttle (12V), then the effectiveness will be diminished.  Unlike a battery which provides a steady voltage for most of its discharge cycle, when a capacitor is discharging the voltage starts dropping immediately, and it discharges down to zero volts.   LED needs around 3V to operate at full brightness. If a capacitor is charged up to 12V, it will be able to provide voltage sufficient to keep the LED lit bright enough longer than if it was charged up only to 6V (if you operate your train at 6V for realistic speed).

Also, the drumhead light circuit is likely slightly different than the interior lighting unit, so the connections (or modifications to it) will likely be different than what I'll present here.

[randgust]

OK, well, I'm OK with basic stuff but here's my question.    I transplanted the drumhead out of a Kato El Cap set so that it was at the rear end of a standard coach.   Works quite well, but even with 8x8 end axle pickup and some added weight I'm still getting flicker.    I have Rapido easy-peasy boards in for all the car lighting, but this drumhead is still a minor headache.

I'd think I'd be able to add a capacitor to this somewhere?   The Kato part is 15606.  Black wires go to the track feed (DC) and the LED is at right.  The magic black spot is ....what?    Something is limitiing current/voltage so the LED is constant, but it flickers, so capacitance could be on either side of the circuit (feed or LED).



Link:  http://www.randgust.com/Kato%2015606%20light%20board.jpg

I know this can be done because I must have about a dozen various Richmond Controls constant lighting boards and headlight boards, they have enough capacitance that the marker lights stay on for 15 minutes after track power shuts off, so saying 'it won't work' doesn't cut it here.

[peteski]

Richmond Controls is a whole other ball of  wax.  He likely uses Super-Caps and very low current LED.  These Kato boards are different. The circuit I'm going to present will just reduce the fast flicker caused by momentary loss of contact as wheels travel over tiny dirt particles. And as I mentioned, keeping the wheels clean does help in eliminating flicker.

If you want Richmond Controls type of circuit, you have use one of those.
Your photos shows enough details for me to try coming up with instructions how to add my anti-flicker circuit.  I'm close to posting instructions for the circuit for  milw156.  I have the diagram - now have to create a component list and additional instructions.

[jbonkowski]

Has anyone wired in capacitors to the Car lighting kits(V2)? I was given some a while back, but the flickering is driving me nuts.

I have installed caps into a Kato car with the latest lighting kit to try to get rid of flicker. They were the large yellow ones fit at the end like someone posted in a picture below.

It worked, sort of. The LED light stayed "on" for about 5 seconds. However, the brightness of the LED dimmed as soon as the track power was cut, and stayed at that lower brightness level for those 5 seconds. Since LED brightness is controlled by the current, a lower current/higher resistance will make the LED dimmer. The caps still discharged, but the current coming out of them was lower than the current sourced by the track.

So the end result was still a flicker when passing over dirty/dead track, just less of a flicker. It might be possible for me to re-design and select capacitors (and wiring) that will maintain the same level of current/brightness through a power interruption.

it wouldn't be hard for Kato to add capacitance to their lighting kit board to reduce flicker. There is a lot of empty space on it. I'm not sure why they didn't do it. The cost is pretty minimal.

Jim

[peteski]

Flicker eliminator for Kato Rev.2 light boards for passenger cars.



The Kato lighting circuit board utilizes a quad-diode circuit (the 6-terminal component wired as a bridge rectifier), and instead of a typical current limiting resistor, it uses a constant current diode, which limits the LED current to around 15mA. That results in a brightly glowing LED.

This circuit should eliminate flicker due to very brief power interruptions often encountered with Kato passenger cars. It does not provide longer time keep-alive lighting. It is also not a substitute for keeping the wheels and track clean.

I am presenting 2 versions, with minimal differences between them.Version 1 is slightly more complex to wire and it provides slightly better performance. Version 2 is simpler to wire up.

The wiring should be self explanatory. I show colored wires for clarity.  Start by scraping off the solder mask coating in the area marked by the small orange rectangle on the PC board. Make sure to create a clean bare copper patch to be able to easily solder the wire. Always use flux when soldering, and pre-tin the wires to make the soldering process quicker.  The tantalum capacitors shown (labeled 157 20) are 150 µF 20V for a total capacitance of 450 µF . In example 1 the original constant current diode is removed, and the wires are soldered as shown to the solder pads.  The component layout or wire placement is not critical.  It might actually be more convenient to drill holes near the wire connection points on the PC board (but without creating a break in the copper traces) and running the wires under the PC board.

When a source of voltage is first connected to a discharged capacitor, for an instant it appears as a short circuit . R1's function is to limit the charging current of the capacitors to around 120mA.  Otherwise, a whole train of flicker-free light equipped cars might trip the DCC booster's breaker. Also, tantalum caps can be damaged by uncontrolled initial current surge.

Diode D1 is optional - it provides marginally better performance. If using the diode, pay attention to its polarity.  Cathode (the end with a black band) is connected to the negative lead of the capacitors.

I recommend a total capacitance of at least 400 µF.  This can be achieved by connecting multiple capacitors in parallel (as shown in the diagram).  Tantalum capacitors will likely be used as they are more compact than aluminum electrolytic caps. For safety reasons I highly recommend using capacitors rated for 20V or higher.  Tantalum capacitors are very sensitive to over-voltage, and when they fail, they produce a thermal event (spectacular fire) which is guaranteed to damage the plastic car shell where they are installed.  Do not be tempted to use caps rated for 16V.  Also, it is safer to buy capacitors from a reliable industrial suppliers of electronic components (like Digikey) than generic caps from Chinese sellers on eBay.

I recommend using multiple capacitors because if a 400 µF 20V capacitor even exists, it will be rather expensive.  Plus in my experience, the larger value capacitors are more prone to self-destructing.  Smaller value capacitors are also smaller physically, so it should be easier to arrange them in the limited space inside the model.

Last recommendation I have is to (if you have the capability) burn-in the capacitors before installing them in the car. That will further reduce the possibility of the caps burning up inside your expensive model.

Parts list (using Digikey part numbers).  Including both leaded or SMD versions for resistors and diode.

R1 - 100 ohm 1/4W resistor Part# CF14JT100RCT-ND
R1 - 100 ohm 1/4W 1206 SMD resistor Part# RMCF1206FG100RCT-ND

R2 - 560 ohm 1/4W resistor Part# CF14JT560RCT-ND
R2 - 560 ohm 1/4W 1206 SMD resistor Part# RMCF1206JT560RCT-ND

D1 - 1N4148 diode Part# 1N4148FS-ND
D1 - 1N4148 SMD diode Part# 1N4148WTCT-ND (very small component)

Cx - any tantalum capacitor rated 20V or more. Here are some examples:

Tantalum Polymer Caps
CAP TANT POLY 100UF 20V 2917 (low profile) Part# 718-T52E5107M020C0055CT-ND
CAP TANT POLY 100UF 20V 2917 Part# 478-11484-1-ND

CAP TANT POLY 150UF 20V 2917 Part# 399-19581-1-ND

CAP TANT POLY 220UF 20V 2924 Part# 478-13377-1-ND

Standard Tantalum caps
100 µF Molded Tantalum Capacitors 20 V 2917 Part# 478-TAJD107K020SNTVCT-ND
CAP TANT 150UF 20% 20V 2917 Part# 399-9750-1-ND

Notice that the price is much lower when buying them in larger quantities.
Make sure to check the capacitor's physical dimensions, and whether they will fit in the available space in the car.

Here's some recommended reading about handling, and possible problems with tantalum caps:
https://www.therailwire.net/forum/index.php?topic=53888.msg740073#msg740073 and the remainder of that thread.
https://www.therailwire.net/forum/index.php?topic=50484.msg686525#msg686525 and he remainder of that thread.
And if you are still reading, there is this  thread: https://www.therailwire.net/forum/index.php?topic=35869.0
And this one https://www.therailwire.net/forum/index.php?topic=43648

The burn-in info is mentioned in the above threads. Basically it involves connecting the capacitors (using correct polarity) to a source of 18VDC (like a battery pack for a cordless drill) to weed out the weak caps.

I did not include this info to prevent anybody from using tantalum caps, but just to make you aware that there are some risk involved, which can be minimized by doing the burn-in, and using caps rated 20V or higher.

[peteski]

Randy, I came up with this hookup info without seeing the back side of that PC board. I'm 99% sure it is correct, if possible I would like to see a photo of the backside of the PC board.

This is a flicker eliminator for Randy's drumhead lighting unit.  Will work in DC and DCC. Components used are the same as for the lighting unit covered earlier.

This circuit should eliminate flicker due to very brief power interruptions. It does not provide longer time keep-alive lighting. It is also not a substitute for keeping the wheels and track clean.



I recommend a total capacitance of at least 400 µF.  This can be achieved by connecting multiple capacitors in parallel (as shown in the diagram).  Tantalum capacitors will likely be used as they are more compact than aluminum electrolytic caps. For safety reasons I highly recommend using capacitors rated for 20V or higher.  Tantalum capacitors are very sensitive to over-voltage, and when they fail, they produce a thermal event (spectacular fire) which is guaranteed to damage the plastic car shell where they are installed.  Do not be tempted to use caps rated for 16V.  Also, it is safer to buy capacitors from a reliable industrial suppliers of electronic components (like Digikey) than generic caps from Chinese sellers on eBay.

I recommend using multiple capacitors because if a 400 µF 20V capacitor even exists, it will be rather expensive.  Plus in my experience, the larger value capacitors are more prone to self-destructing.  Smaller value capacitors are also smaller physically, so it should be easier to arrange them in the limited space inside the model.

Last recommendation I have is to (if you have the capability) burn-in the capacitors before installing them in the car. That will further reduce the possibility of the caps burning up inside your expensive model.

Parts list (using Digikey part numbers).  Including both leaded or SMD versions for resistors and diode.

A list of possible capaciotors:
Tantalum Polymer Caps
CAP TANT POLY 100UF 20V 2917 (low profile) Part# 718-T52E5107M020C0055CT-ND
CAP TANT POLY 100UF 20V 2917 Part# 478-11484-1-ND

CAP TANT POLY 150UF 20V 2917 Part# 399-19581-1-ND

CAP TANT POLY 220UF 20V 2924 Part# 478-13377-1-ND

Standard Tantalum caps
100 µF Molded Tantalum Capacitors 20 V 2917 Part# 478-TAJD107K020SNTVCT-ND
CAP TANT 150UF 20% 20V 2917 Part# 399-9750-1-ND

Notice that the price is much lower when buying them in larger quantities.
Make sure to check the capacitor's physical dimensions, and whether they will fit in the available space in the car.

Here's some recommended reading about handling, and possible problems with tantalum caps:
https://www.therailwire.net/forum/index.php?topic=53888.msg740073#msg740073 and the remainder of that thread.
https://www.therailwire.net/forum/index.php?topic=50484.msg686525#msg686525 and he remainder of that thread.
And if you are still reading, there is this  thread: https://www.therailwire.net/forum/index.php?topic=35869.0
And this one https://www.therailwire.net/forum/index.php?topic=43648

The burn-in info is mentioned in the above threads,. Basically it involves connecting the capacitors (using correct polarity) to a source of 18VDC (like a battery pack for a cordless drill) to weed out the weak caps.

I did not include this info to prevent anybody from using tantalum caps, but just to make you aware that there are some risk involved, which can be minimized by doing the burn-in, and using caps rated 20V or higher.

[milw156]

Thank you Peteski, this is most appreciated!
Rick