Flickering LED firebox light

Hard to see in the video, but I can assure you in person the effect is pretty cool, I've done a few of these, and I bought up a bunch of Dollar Store tea lights to have a stock of these flickering LED's.  That's the cheapest place you'll ever find them, you just have to rip them out of the candles.

The cab light and markers and firebox are all lighted now.  The cab is painted black and gauges detailed. need some figures and the headlight is on order, then project will be complete.  The firebox glow is the best Ive seen.  looks like a hot fire. its great!

I like the detailing in the cab, I have a couple like that, and I'd like to do more.

thanks john. more touch up work, I used a tiny stiff brush with a point and its still hard to make it perfect!  i still have to decide woodland scenics, arttista, or MTH figures.  still looking.   I thought maybe that glow might appear below the Ash pan area too, ill have to see if that happens.  cant find out until the headlight comes and I can put it together

chris

The beauty of the cab detailing is you don't truly need it 100% perfect, typically you're not going to look quite that close.

Well, im a little picky with stuff.  my wife says that all the time!  lol! when I bought my new Ram, I painted the undercarriage with 3 coats of frame paint in gloss black.  my wife just shakes her head. I say, hey, Ill have this thing for 10+ years and its still going to look like new!  hahaha. 

Watch your mailbox, I'm sending you a bunch of steamer shells to detail the cabs!

Great work. 

Do have a parts lists and a circuit diagram for your flickering LED mod?

Copter

Here you go.  This is designed to run directly from 16-18V track voltage in command mode.  The flickering LED's are bought at Dollar Stores, ripped out of the battery powered tea light candles.

FYI, the 22uh choke is for DCS compatibility, it's a pretty cheap component so I put it in most of the conversions I do.  The diode, cap, and resistor should explain themselves.

I did all of this as john says in the diagram and they work fine off my headlight feed on the engine Purple + and used the other headlight feed, a lighter blue off the bottom of the fixed bulb feed to power my markers, cab light, flickering setup and the LED headlight.  still waiting for my headlight............... to finish

You can lower the resistor value and skip the diode for running off 6V from the PS/2 lighting, you'll get brighter flickering firebox effect.  The above schematic is designed to work from 16-18 volts track power.

oh  yeah, I think the next time ill cut the resistor.  it should be ok.  they are not any brighter than with the battery.  I cant wait to start making more.  got 2 more engines. THe articulated 2-8-8-2 has this tiny hole.  not even opened up enough, so it will need drilled.  THe dremel will open that up nice

Looks awesome. I wish I could grasp the advanced electrical side of this hobby.

Well, this is more the "basic" side, and we'll be glad to help you through it if you want to add one.

HAHA, When you start talking diodes, resisters, and flux capacitors I'm lost. I'm still at the VERY basic level.  But when I need help I know where to go. Love this forum and the knowledge people have.

With your flux capacitor you've clearly pulled away from the pack!

https://www.youtube.com/watch?v=Uln1eU-k-Nw&feature=c4-overview&list=UU_lca3Q0uAVuf0skoq-2vnQ

this is the test with the fire in the box.  looks great, I think. 

chris

Important safety tip, thanks!

I experimented w/ Gunrunnerjohn's schematic on my breadboard.  Power source: accessory line (14V AC) from a Lionel CW80 transformer.  I added a bridge rectifier to convert AC to DC. 

The 470 ohm resistor in the circuit felt a bit hot after a few minutes.  Would a current regulating chip such as a 7805 yield less heat?     

Use a diode, it results in a lower DC voltage and thus less power dissipation in the resistor.  If you measure the voltage across the resistor, it's probably around 15 volts.  That would result in a power dissipation of close to 1/2 watt.  A regulator won't change the amount of power dissipated from the supply.

On your circuit board, I see you have a bridge rectifier and also a diode.  Just remove the bridge and power it with the diode. 

It should, and you can also use a 1/2W resistor. 

Originally Posted by gunrunnerjohn:

What's going on is the capacitor charges to the peaks and thus you have a higher input voltage to the circuit.  However, the capacitor is required for the flickering LED to work properly.  You can move the resistor to the other side of the cap and reduce the peak it sees.  You can also simply use a larger resistor if you have 18 volts into the circuit.

If the voltage at the junction of the cap and diode is 14 volts DC, the power in the resistor will be .44W for 40ma, so a 1W resistor would be the ticket.

Re: "You can move the resistor to the other side of the cap and reduce the peak it sees."

Would putting the resistor behind the capacitor transfer too much power to the LED & burn it out?

Below is the scenario I'm referring to.

Nope, that will work just fine.

If the resistor is placed before cap, won't the cap only charge up to a few volts?  In which case on each half-cycle, wouldn't the cap be starting at a low voltage that it would sag enough to potentially cause the LED to stop operating (60 times/sec)?

Do you know the V-I characteristic of the Flickering LED as you apply more than 3V (or whatever it's meant to operate at)?

Separately, in the earlier 2 LED application, why can't you put the 2 LEDs in series?  You have enough voltage and this would cut the current in half for the same brightness.  Just curious...

It works fine Stan, I tried it with a 100uf cap.  However, I think the better method is with the cap in front of the resistor as you mention, and that's how I've always used them. 

Curiously, I have a 1/4w 470 ohm resistor in series with the flickering LED and I have around 18 volts DC across the cap.  The resistor isn't even getting that warm, it stabilized at 40C.  With two LED's in parallel, 1/2W should be plenty for the resistor. 

The flickering LED's have a problem when they're in series, they interact and don't have the same random pattern.

I did not notice heat but the voltage on the input of mth headlight is 6 

Right Chris, you don't have to drop much voltage, hence you're not dissipating much power in the resistor.  The LED(s) are operating at a nominal 3V, so you only had to drop 3 volts across the resistor.

Correct, that's the function of the diode.  One concession to more safety for the LED would be an additional 100 ohm resistor between the capacitor and the LED.  I'm thinking that Stan may have a point about the capacitor potentially charging past the optimal voltage for the LED.  It works fine, but in the interests of long life...

Gunrunnerjohn,

What software did you use to draw up the electronic schematics posted in this thread?

Copter

Those are done in TinyCAD, a free schematic capture program.  It's a quick and easy way to draw schematics.