LED lighting for dark Trolleys

Boy, if you can get electricity for 10 cents KW/HR, you're doing a lot better then I am!  I live in PECO country, it's around 15 cents.

I didn't actually take all the measurements and log them, but I was taking a few.  At the 2 minute mark the voltage was 3.6V across the caps.  When "fully" charged after a minute, the voltage was 4.95V across the caps.  That was from a full discharge, I didn't do any additional measurements.  The lights remained on slowly dimming for over five minutes.  The resistor I was using was a 39 ohm, but I think I'd cut that to the 33 ohm for the "production" version.

If you have three LEDs, the parts list is one 5 ohm 1W resistor, one 1N4003 diode, two 2.5F 5.5V supercaps, and a 33 ohm 1/4W resistor.  You'll need the adjustable 5.5VDC 1A power supply to provide the power.  Since the peak power is only for a short time, you could do this with an LM317T, diode, cap, and a 22uh choke for DCS compatibility.  You can also do it with the canned power supplies we routinely point out on eBay.

Like I say, this isn't a "perfect" solution, but IMO it looks pretty good, it's dirt simple, and pretty inexpensive as well.  For more LEDs, you can add a couple more super-caps.  Obviously, that will extend the "full" charging time, if you have a reasonable charging time between the station stops, I think it should work out.

My advice would be to do a test run with one set of components and see if the results are satisfactory.

Times:

I made it to the layout this afternoon.   It was a good thing.  My guesses were definitely off.  I timed the trolleys using a Z4000 at 12 volts and each stopped for 34 seconds and ran for 23 seconds in turn repeatedly.

Not being schooled in the technical aspect of this project, I’m indeed fortunate to have this forum and those who are good at it.  At the risk of stating the obvious or sounding Blonde, all I can deuce from these numbers is that whatever type, size or quantity of capacitors, they must charge faster than they fade.  Do I hear a Duh?

Fortunately, one of my best railroad buddies has experience with these type of parts. There are other men in the club that understand them too.

I have a good feeling about all this. Thank you!  

Photos of open trolley and layout stops:

There appears to be plenty room in these trolleys.

Will be gone Friday to Thursday.  

Missed an attachment

John and Stan - as usual, your electrical/electronics musings are very educational - if not entertaining - and way beyond expectations in terms of helping out a fellow modeler.  I do have a question - originally posed 'a while back' by Bobby Ogage - which is why not use a battery and a charging circuit instead of a capacitor-based design.  Doesn't a battery approach provide greater flexibility in terms of how the system is operated (especially if the run time is shorter than the stop time)?

Not really. A cap, or super caps are ideally suited for this application time wise.

A trip to Radio Shack & I can get 4 grains of wheat to light for 30 seconds with normal caps in the supply, and it all could still be smaller than a aa battery.

Size and longevity? They win. Charge cycle ability, they win.

It will also be an automatic on and off, no power switch to forget about, or charge to keep up. It will outlast most batteries.

 Now these guys have a shorter time to work with, it especially suits the need.

Any nitpicking is an attempt at "the perfect circuit", time, ease, expense, etc. There is more than one path here.

Once done, he may never need to touch it again, ever. 

The battery charges much slower than it would discharge, so IMO would not be an ideal candidate for this job.  The superCAP seems a perfect fit, you can fast charge it in a short time, and it'll keep the lights on for plenty of time.  Seeing the size of the trolleys, I'd say that the three LED's inside would be plenty, I'd use some wide-angle ones to spread the light. 

As far as room, the superCAP and associated components are pretty small, so that won't be an issue in almost any environment.  Here is the 2.5F 5V superCAP I spoke of.  Diodes and resistors can be had at the same site. 

Let me sneak a few more questions in before you go.  You have answered all my questions to date (and thank you for that).  So continuing on to the proverbial "20 questions"

9. I see these trolleys have directional lighting - appear to be LEDs.  You previously mentioned only the interior lights need to stay on at the stop.  So it's OK to turn off directional headlights while stopped?

10. Roughly how long is the trolley car?  I'm thinking you might be able to use LED lighting strips often discussed for passenger cars.  They come in increments of 2 inches.  They may need to be modified, but I think might result in a net-positive wrt easy-of-assembly.

11. How do you stop trolleys at the stations?  Are there relays that cut power to each station block?  I still have not given up on a variant of Dale H's notion of keeping some variant of track power applied at a station stop.

Stan still wants to make this complicated.

Adriatic and GRJ pretty much say it all but here's a couple additional comments:

1. A 9V style NiMH might be rated, say, 8.4V 120 mA-Hr.  So let's do the back-of-envelope math.  That's 8.4V x 0.12 Amps x 3600 sec = 3629 Joules.  So clearly a charged battery can store a whopping amount of energy relative to a supercap and relative to the task at hand (maybe 50 Joules or so).  So it's not that it won't work!

2.While maybe apples-oranges comparison, it's interestingthat MTH initially started with rechargeable batteries in their PS2 electronics, which an aftermarket company then made a supercap (BCR) alternative for those batteries, and then now MTH uses supercaps in their PS3 electronics.  Yes, a lot has been going in terms of improving the supercap technology and cost during that period but again just an observation.

Gunrunnnerjohn:

I have someMTH ‘proto sound’ engines and have replaced the batteries with 9V-Nimh rechargeable batteries.  I actually had these in mind when thinking about this issue.  Yet, I knew the charging time was definitely too long.  I’ve also had some rechargeable batteries that failed.  For those reasons, I joined the O Gauge Forum.   I knew it was the right place to find a solution and I’m greatly pleased.

John, I agree with your solution.  You nailed it.  It’s exactly what I need.  I do want to keep the headlights as they are.  Three wide -angle LED lights sounds perfect.  Are they attached together or separated?   

 A parts list and schematic will be greatly appreciated.  I’ll gladly take it from there.  

Big thanks everyone!  It’s been a trip.

Gentlemen - as usual, this has been a very illuminating discussion...

(I had some other puns too - ... keeping on track, positive, well grounded, etc.  but I'll spare you...).

Here's a schematic from track power to the three LED's.

Point taken.  I think the supercap solution as proposed will work so I agree "case-closed."  So test is over, put down your #2 pencils, and hand in your papers.

But as a discussion forum, there are two comments.

1. From an assembly point of view, I think the 12V LED strips are economical (pennies per LED) and easy to work with for wide-angle car lighting.  That said, you can get low-cost $2 (or so) eBay modules to step-up the 5V supercap output to effect constant-brightness lighting using these strips.  It is more complicated.

2. I think the lowest cost solution is to use a derivative of Dale H's ideas  That is, rather than remove track voltage at the station stops, you could send rectified AC track voltage via a diode to each station stop section.  Such a diode would cost maybe 25 cents.  So when running, the stations get regular 12V AC (or whatever) from the Z4000.  When stopped, the stations get 12V AC thru a rectifier...or just the + cycles of the AC waveform.  In each trolley you install a DC detector circuit.  When DC is detected, it cuts off power to the motor.  When AC is detected it allows power to the motor.  DC detectors are used for whistle or bell triggering in conventional control and cost maybe 25 cents in parts.  Then add a $1-2 relay.  No supercaps, no batteries, etc.  Since we're only powering LEDs, the rectified 12V AC track voltage has enough power to keep the LEDs on.  There is something ironic that here you have a trolley physically in contact with a track with virtually unlimited power available but it can't be had!

The problem with the 12V strips, which I did consider, was that you need a higher voltage to drive them, hence you need at least three supercaps.  With my scheme, you can probably get away with one supercap, though I show two.  Given the new information of 35-40 second endurance, I suspect one of them would do the job. 

I don't know about the lowest cost, but that solution seems a whole lot more work that the simple circuit and wiring of the LED's.  I have no doubt that can be made to work, but I think the KISS principle would certainly apply here, at least IMO.  I'm not seeing a downside to just lighting the LED's and leaving all the track wiring, motor wiring, DC detection, etc. at the door.  If the costs differ, it's only by a dollar or two.  I figure my circuit is $7-8 in parts if you use one supercap, all the other parts are dirt cheap generic parts.  You don't need the 22uf choke if you aren't worried about DCS compatibility, which I suspect is not an issue on these tracks.

1942guy now has a couple of options to choose from.

Here's a schematic from track power to the three LED's.

Is it possible to get a parts list too for Dummies like me so I can place an order?

Just to be clear, they can turn OFF when stopped as they do now?

OTOH, if you want them to stay ON like the interior lights, GRJ will have to modify his schematic a bit.  Hard to tell from photos but it appears the headlight LEDs go thru the bump direction slide switch.  So the circuit needs consideration to maintain the correct headlight LED.  Additionally it appears 1K (?) resistors are used for the headlight LEDs to run at track voltage so these resistors would need adjustment to operate from the ~5V supercap.

Stan is, of course, 100% correct.  I inferred from the previous comments that it was OK for the headlights to go dark until the trolley started up again.  If that's not the case, it would add some complexity, especially with directional lights.

Q1 Does the trolley reverse? It is stated it runs on a loop.

Q2 What circuit stops the trolley?

Q3 what transformer is used?

Dale H

We only want LED overhead lighting.  The Headlights going on and off is okay and preferable to us.  Our club consists of seniors of various talents and abilities.  Think about it.  There is a slight advantage to this.  Maybe it's not a huge advantage but we like it. 

Appreciate your being thorough.  Got to pack now.  Have a good weekend.

If the headlights going out is not a problem, I think we have what is going to be the simplest solution to this issue.