Large Scale Central

Flicker free module for track power bulbs?

Electronics Power and Sound
#1

Wondering if there are any flicker free modules to purchase that work with g scale track voltages and bulbs?

My sister has a very simple Christmas tree circle of track and it runs on track power. I got her a nice little Hartland caboose (will be a Christmas present this year). It has lighted markers and some interior bulbs as well. But it flickers badly. I kind of forgot how bad basic track power (no DCC either) is for flickering lights.

Strange is the USA trains NW2 pulling the train I have for her does not flicker at all. And it too has bulbs. Likely some type of flicker free circuitry in there. Or maybe better power pickups.

I’m not sure if there are any circuits or modules out there that will keep the flickering down with bulbs…most seem to work with LEDs. And I don’t want to use batteries. I don’t want her having to take the caboose apart to change batteries. She also lives in the Chicago area and I’m in California…so I can’t easily fix it for her.

Any ideas?

Oh almost forgot. I haven’t opened the caboose yet, but I think the bulbs are likely 18v or so since they run on track power and I highly doubt there is any voltage regulator or even any kind of circuitry in there. Simple wheel wipers and bulbs wired directly to them…is my guess.

#2

Attach a 1 or 1.5 amp bridge rectifier to the power pick-ups. Put a 35 volt electrolytic capacitor in parallel with the bridge output observing proper polarity. The capacity (mfd) of the capacitor acts as a reservoir when power levels drop.

The more mfd, the bigger the reservoir. I would try something in the range of 3,500 mfd for starters and go from there.

#3

Appreciate the info.

I have some 35 amp bridge rectifiers that were used for various other projects, almost identical to these:

http://www.allelectronics.com/item/fwb-356/35-amp-600-piv-bridge-rectifier/1.html?extra=a%3A2%3A%7Bi%3A0%3Bs%3A40%3A%2203823345592a403b2f4a37a59384e7ab28f02be1%22%3Bi%3A1%3BN%3B%7D

They are large in size but space isn’t an issue inside this caboose. Or do I need the smaller amp 1 to 1.5 like you mention?

Also any diagrams of the wiring? I think I know how to wire this, but a diagram would help.

#4

35 amps is fine.

left and right wheel pick-ups to the ~ and ~ on the bridge rectifier.

  • on bridge to + on capacitor AND one leg of bulb(s)
  • on bridge to - on capacitor AND other leg of bulb(s)
#5

Just to answer the question, many lights on USAT are fed from regulators, so there can be some buffering in those circuits.

Greg

#6

Thanks all, and Greg that makes a lot of sense.

I actually think the flickering is due to how the power pickups were designed. On this particular caboose the marker lights are only powered by one wheelset. Usually you’ll see power pickup from both trucks. But this is one truck with one wheel picking up power. Actually surprised it works as well as it does with just one wheel.

I have some extra LGB ball bearing pickup wheels that I’ll use on this caboose. Should be a lot better. But I’ll also put in the cap and rectifier.

It’s kind of fun working on this Christmas tree train set. Reminds me of my Christmas train…which grew and grew every year. And now it’s outdoors (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)

#7

att Doti said:

Oh almost forgot. I haven’t opened the caboose yet, but I think the bulbs are likely 18v or so since they run on track power and I highly doubt there is any voltage regulator or even any kind of circuitry in there. Simple wheel wipers and bulbs wired directly to them…is my guess.

Hi Matt… The bulbs in the marker lights in Hartland caboose are 12 volt, not 18… If 18 volts hits them, they will go dark in a hurry. I just talked with Phil Jensen from Hartland and he suggested you wire them in series rather than parallel as they come from the factory. That will drop the intensity of the brightness nicely and protect the bulbs from blowing if the voltage goes too high… You don’t really need a bridge rectifier using the bulbs that come with the caboose. They will work in forward or in reverse polarity. I wish I could show you how to wire a capacitor in the circuit. Todd or Greg are the guys to go to for that… (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)

#8

The rectifier is needed for a capacitor “keep alive” circuit.

#9

Another question,

Should I put the capacitor on a heat sink or similar? Wondering if it gets hot and then it might melt the caboose plastic a bit.

#10

Capacitors don’t get hot. If they do something is wrong. The rectifier might get warm, but even that should not get hot enough to cause any issues.

#11

Thanks David.

#12

For constant brightness I would use leds and control the voltage with a regulator. Also this reduces the current and a smaller capacitor can be used, or keep the large one and see the leds stay on for a long time with the power removed.

Supercaps can keep leds on for many seconds, great for DC users when changing direction.

#13

Matt, on cabeese, I put LGB or better ball bearing wheels on ALL axles, giving me 8 wheel pickup.

I will still get some flicker, but Idon’t mind. Eventually I will put a FW bridge, big filter cap and use the CL2 regulators for the LEDs… that should be really flicker free.

Greg