My latest project has been to reduce the flicker and “brown outs” of my interior lighting. The biggest improvement came when I converted all my lit cars to the Walthers trucks with 8 wheel electrical pick up.
To take it a step further, I went on a quest for a capacitor and/or a battery that would take care of any remaining dropouts. There’s no rechargeable battery small enough or light enough that will work for me. The rechargeable cell/button batteries that I could find cannot delivery 20 ma continuously (average draw per car with 6-8 LEDS). The best I found could do 0.5 ma. Any rechargeable battery that can deliver that current is way too big and heavy for my interiors. I’m not interested in any battery that needs replacement after 10 hours of use either. I want to minimize handling and “popping open” my cars. Inevitably, something happens that I have to fix. So, that left capacitors.
I found a small, lightweight SMD capacitor that is 1500uF at 4volts dc. With the 8 wheel pick up, 3volt light rails and 20ma draw, it looks like a set of 3 of these caps in parallel, with 10 ohms in series with the set appears to be doing the trick. The caps easily fit in the roof area of my cars, in between the light rails. I could easily put a dozen of these caps in the roof area. The caps are small enough to put in lockers or dark rooms with the shades pulled, etc. The voltage on these caps has a limit of 4v dc. My regulators are 3v (gives the caps a little room to work). I AM STRONGLY AGAINST using even one of these high capacity caps across the output of a regulator without a series resistor. The cap will initially look like a dead short to the reg
You’ve provided the answer for a question that I have been planning to address. With a large passenger roster, a number of brake vans and full cabooses of various types and plans to operate night trains in a darkened room, I was looking forward to a period of experimentation. You’ve probably saved me a good many hours of time, not to mention silencing a lot of uncouth language.
Considering the total size of my roster, I may have to take Mouser up on the 100 capacitor deal.
Amazing work there, DC! [8D][tup] You really live up to your name.
Those surface mount caps sure save space. What sort of power interruption interval can the capacitors span? Do the LED’s fade out when power is removed? And where did you get that flex braid?
Good solution, although a little pricey. I think the Rapido Easy Peasy, at about $15 list, is an easier solution. They use the LEDs, but with 2 small batteries. I have 4 of the Rapido cars, and have started equiping my Walthers that do not have their lighting units with the Rapido’s. I have a small fleet of Bachmann Spectrum heavyweights, and they are the worst as far as flickering, and darned near impossible to remove the roof and put it back on with the lights still working!! As soon as all my cars are lit, the Bachmanns will be next!
I knew it! I knew it! Someone was going to ask me for numbers. [banghead]
LOL
Seriously, though, thanks for the kind words. My AC theory is pretty rusty, and my calculus is all but faded away, but I will rough out some numbers for you. Give me a little time to do some crunching, and I’ll get back to ya.
Yes, the LEDs fade out. They always will with an RC circuit.
I got the flexible wire from junk bins at work, and don’t know any part numbers. I stripped the insulation off to make it more flexible. It’s about a 22g, multi-stranded (at least 100 strands, maybe 200), twisted pair computer/printer wire from a ribbon cable. I would think Mouser, Digikey, Newark, etc. would have something like it. That’s all I know.
P.S. Had a little scare there when I came back and couldn’t find my thread.
Don’t worry about exact numbers, because if it fades slowly then it can keep the lights on across a significant gap. I only meant a really rough estimate, based on the LED to cap ratio you’re using. [swg]
No problem. This is for my Walthers set up with 6 LEDs, 3V, 4500uf, 10 ohms. The perception of brightness/illumination in relation to the impedance at any given time is a little tricky, but here goes: about 100ms-200ms to the start of noticeable fade, and around 600ms-800ms to complete fade out.
Thanks, Karl for your interest. [:)] It might be a viable option; I’m not sure.
At 20mmx5mm, it’s a little large for my application. It might be a better solution for someone else.
Also, these are designed for memory backup, which is typically in the hundreds of microamps today. I wonder how long they will last, or even if they can deliver 20 - 40 ma. Can they take the duty cycle? The large change in capacitance and internal resistance over time concerned me, also. The price/capacitance is a real plus - just not sure of its performance in my application.
I hope that I haven’t given the impression that this is my final solution. As far as I am concerned, the “flickering” issue is still open. I will continue to look for smaller, lighter, and cheaper devices and solutions. I think it won’t be too long before we will see a small, rechargeable battery that can deliver. I hope ideas, suggestions and other solutions for improvement continue to appear here. I have already bought all the capacitors I need, and I am going with this for now.
If someone was going to start from scratch (trucks, LEDs, regs, caps, resistors, etc.), this would be a pricey deal, indeed. It wasn’t so bad for me. I needed to upgrade/correct my Soho and Rivarossi trucks anyway. I got resistors, FW bridges and hook-up wire from liquidators and Ebay for dirt cheap. 8 LEDs, regulator and 3 caps average $25 per car.
In the short term, there are cheaper, easier solutions out there. How many batteries am I going to have to buy, store, and properly dispose of in the next 10 years? How many times am I going to handle my cars to change batteries? I don’t want every car lit end to end, ceiling to floor. I want to light specific areas. I want different degrees of illumination, and effects. I can slip an LED in a shrink tube and make a spotlight. How much time will I spend bashing a commercial light kit? In the long term, and with the present technology, batteries are not the easiest solution for me, but it’s nice to have viable options.
I spent some time last night installing caps in my cars, and decided to experiment on one car. I tried a 30 ohm series resistor on a 4500uf, 6 LED car. The total fade out time went to a least a second. It was noticeable. This means, though, that the time to the-start-of-noticeable fading would be shortened. Increasing the capacitance now would increase that time again along with the fade out
It has come to my attention that the application of large capacitance could be a problem for DCC restarts due to the inrush current. I don’t know yet how much is too much, but having just a bridge and regulator (<$2) should make a lighting system compatible with DCC - just won’t do anything for the flicker. Also, DCC may require using a high speed Si or Shottky bridge (still about a buck). I have been looking for a DCC system that I can test my cars on, and, also test an RCC system that I’m going to install in my locos. I’m hoping to make the RCC system operable with 13-16v AC, DC or pulse-width modulated power. I plan to start a new thread on the RCC when I have more.
That’s what I’ve settled on for mine. The local club uses DCC, and that’s where I run my equipment (lacking a home layout at this point). Yes, there is flicker, but it’s not terrible at road speed, using Hippie Pickups (and thanks again for the name! [:D]).
I’ve been using just the standard cheapo bridge rectifiers from Radio $hack with no problems so far. We’ll see what happens a little further down the line, though.
I’ve seen that system advertised for quite a while. I thought about picking one up back when the local club was still using the Aristo Craft wireless throttles. The transmitter for both systems is the same, I believe. I look forward to seeing what you come up with there!
Thanks for sharing that experience, Robert. I was NOT looking forward to replacing all my bridges. You have saved me some time. [:D][tup] I still might have to remove the large RC filters, if I want to run on a DCC system. We will see. If your bridges work now, they will continue to work. At an average of 7kHz, it was the diode rec
