Adding LEDs MTH G scale caboose

Looks like a bridge made with 4 diodes and a regulator. .You could circuit individually LEDs from the 5 volts DC with a 100 ohm quarter watt resistor in series to each LED in proper polarity.

Here is my post on caboose lighting using individual LEDs  for a variety of situations.

LINK

Here is a 7805 from scratch

LINK2

Dale H

Thanks Dale! My brain is stretching!

They're using the middle terminal also and I got lost. I'll test the outside pin and see what the voltage is or if it blinks, right?

Just take a couple more photos of the top side (different angles) and the bottom side and I'll draw out the schematic for you and post it.  It would be good to have it for the record.

The board is labeled 2003.3.3.  I'm just guessing but if this refers to the year 2003, white LEDs suitable for interior lighting were still a bit spendy back then.  I'm not sure what you mean by a component covered in glue.  I see the box labeled IC as shown, is this what you're talking about? 

If 2003 a separate circuit, IC, chip whatever might have been used for blinking an LED  Of course now days you can buy a blinking red LED with the circuit integrated into the LED package itself for 25 cents or so.

Yes, that's what I was talking about "IC". I put a couple volts to the red LED and it did not blink. So I guessed it must be the circuit? Thank you.

Edit: could I or should I put in a larger cap?

The blinking circuit is under the black resin "glue" on the bottom of the board.  This is so-called COB (chip-on-board) packaging.

It's a curious design - note there's NO input capacitor before the regulator IC.  Perhaps this was done to save a 5 cent DCS inductor/choke?  Who knows.  Plus, with only a capacitor on the output side of the regulator, this makes it problematic to add more output load (additional LEDs). But as the designer is not here to present a differing opinion, here's my recommendation.  Leave the board/circuit exactly as-is with the sole purpose of blinking the red LED.

Then take the two-wires from the "Lamp" connector and run it to your own AC-to-DC regulator circuit as you've already done (DCS inductor + bridge + capacitor + LM2596 module).  Drive 12V LED strips adjusting the voltage on the LM2596 module to suit your brightness needs.  I understand you have not settled on AC vs. DC track voltage.

If you scan the various passenger-car lighting threads you will see possibly "simpler" circuits such as using a CL2N3 current-regulator chip that delivers a constant 20 mA to LEDs.  But I'm mindful that we're talking G-gauge here; so depending on whether we're talking MTH 1:32 OneGauge, LGB 1:22, etc., the interior volume you're illuminating can be over 5 times greater than a 1:48 O-gauge car/caboose.  Hence, I'd think you'd want the power capability of a LM2596 DC-DC module - plus my crystal ball says there are marker lights (LEDs) in your future!

There are other options.  But I'll say this; whichever way you go one of the greatest windfalls to O-gauge lighting has been the 12V DC LED strips...a couple pennies per LED!

Thank you!

I didn't even notice until now that the cap's on the output side.

I wouldn't have known the difference (electrical) anyways!

I think I'll try and get my choke and poly-fuses into the incoming pick-up lines. Does the chip help with the cap on the signal then?

i run some of the #1 Gauge (NOT G scale) MTH rolling stock behind a live steam locomotive and while i don't have any MTH cabooses (the single style #1 Gauge caboose MTH manufactured is not even close to any of the roadname caboose designs), the three cabooses i do run have all be adapted to use an onboard battery to power LED marker lights.  frankly even if i was running with track power i still would consider this option as it removes the usually poorly designed wheel/axle pickup wipers which at best will typically cause flickering lights and add drag to the consist.

batteries will light the marker lights for quite a long time (i mount a switch beneath the frame to turn them on/off) before needing replacement.

cheers...gary

I'm surprised the 7805 even regulates properly with no input filtering.

You could simply replace that board with one of the inexpensive buck/boost power supplies from eBay and have tons of power for LEDs.  The blinking isn't an issue as blinking LEDs are a dime a dozen.

I know this is popular with a lot of users. I wouldn't do it myself. I can't see having and replacing all those batteries while having power available right at the track. I'd rather spend the time and get the electronics package corrected.

the first caboose i modified is going on 3 years of lighted operation and i haven't replaced the batteries yet.  before i removed the axle wipers, the car would travel about 6 inches after giving it a light push on level track.  after the wipers were removed, the same force sent the car 10 - 12 feet.  too many positives with the only downside of spending 5 minutes removing a few screws every ~5 years or so.

i don't run trains in the era of EOT devices, but batteries could also power that simple timer circuit.

cheers...gary

Probably should have fixed the pickups.   They add drag, but they shouldn't add that much drag!

That's a very insightful question.  It does to an extent.  The technical explanation gets involved but the basic idea is as follows.  The inductor/choke isolates the "signal-killing" behavior of a capacitor from the track command signal.  The 7805 chip in its regulation function acts as a variable resistor allowing just enough current to flow from input to output to keep the output voltage at 5V.  Clearly if very little current is flowing, then the 7805 is effectively a large resistor and you get reasonable isolation between the track voltage and the output capacitor.  This is why  I do not recommend adding the interior LEDs to further load the 7805 output.  More load means more current flow through the 7805, which effectively makes the 7805 a smaller resistor, resulting in less isolation to the capacitor.

R-I-G-H-T!!! Sure, got ya.

I have to study some more to talk with you guys. Even when you make it simple like this, ....well, I'm still learning.

 I used to do very well in High school math. I took some college level stuff. When all of a sudden my brain crashed in calculous.....see I can't even spell it anymore.

 My dad lost his job and college went out the window. I started working three jobs and never got a degree. I went back to college twice later on to try, but after eleven years, the magic was gone.

 Luckily, I toured with sound re-enforcement systems and kept sharp in basic skills. I know what you're describing usually. I know just enough, to get into trouble! Thank you all for the patience.

I'll bet you have learned to recognize the magic smoke as it wafts away from the electronics.

Well, one thing they don't teach in college:

https://ogrforum.com/t...rail-cars-and-boxes?

I wonder if newspaper and a brown paper bag works on circuit boards that released magic smoke?  I wanted to see a photo of that smoked DC-DC regulator module that you had to toss because of the odor!

One thing on tour is it has to be right. A lot of people don't realize what they go thru to get the system so no one gets shocked, no hum or buzzing sounds, and all the rigging and on the spot repairs.

 Just to fix mic and speaker cables is a full time job. I've seen plenty burn up for all kinds of reasons. I saw a guy hook up to a panel that he thought was 220 single phase and was old industrial 440 three phase. He fried just about everything.

 I myself had an arc flash event that I was lucky to survive. Someone left the lugs loose the night before and returned the panel to full service with them loose! I'll never figure out how they weren't arcing? As I connected, I found out!

 I like electricity and find Tesla's work fascinating. I didn't want to see it first hand like that!

I always take picture too. I didn't. The grandchild was so upset that he might have caused the failure. It should have failed when I tested it?

 I've learned over the years that if you get rid of it, it never happened.

actually this wasn't an MTH caboose.  the only one i've had to fix (the other two were scratch built for live steam) was an Accucraft brass model and believe me the axle pickup wipers did put that much resistance on its free-rolling ability.  fixing them wouldn't have been an option as most live steam layouts do not support track power.

perhaps MTH uses a better electrical pickup system, but i'd still consider anything as an unnecessary drag.

cheers...gary