"Decoding" an existing DCC installation in an LGB 23450

Greg Elmassian

Registered
8 Mar 2014
6,227
828
San Diego
www.elmassian.com
Country flag
I agree, it is operator error.

But me taking that attitude to a friend who just destroyed something won't make him happy!

So, for me, for inexperienced people, and even some experienced ones, the "safer route" is the way I advise.

On this specific issue, I gotten in so many arguments with a newbie who is really intent on not adding a resistor....

But, for the people who have blown their LEDs, there is normally contrition, and a more careful attitude in the future.

All I can do is give my "best" and "bulletproof" advice... and withstand the guys saying "I have been running LEDs without resistors since there were dinosaurs".... for every guy that lucked out there are 10 guys with blown up LEDs.

Greg
 

JimmyB

Semi-Retired; more time for trains.
Country flag
The easiest approach is to buy the LEDs with the resistors already installed in the wiring like I use.
Most of the LEDs (with resistors) I have seen are for 12 volts, and as I like to use duel colour (White/Red), I haven't seen any of these. As a rule of thumb, I use a 1kohm resistor, and this will light with 9 volts, and is good for 24 volts, I understand LEDs are current and not voltage dependant, but this is easier understood as voltage.
 

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
29,504
3,053
Tamworth, Staffs.
Country flag
Most of the LEDs (with resistors) I have seen are for 12 volts, and as I like to use duel colour (White/Red), I haven't seen any of these. As a rule of thumb, I use a 1kohm resistor, and this will light with 9 volts, and is good for 24 volts, I understand LEDs are current and not voltage dependant, but this is easier understood as voltage.
True..
You can get caught-out, if you have a low voltage switched source, and are trying to use (say) two bi-colour LEDs at each end..
Red and white LEDs have different Vf (forward voltages) and you can have one colour not light, as the voltage across the LEDs is dragged down..

Google 'ledcalc' for a comprehensive calculator..
LEDs is series, or parallel, and any number.

PhilP
 

JimmyB

Semi-Retired; more time for trains.
Country flag
True..
You can get caught-out, if you have a low voltage switched source, and are trying to use (say) two bi-colour LEDs at each end..
Red and white LEDs have different Vf (forward voltages) and you can have one colour not light, as the voltage across the LEDs is dragged down..

Google 'ledcalc' for a comprehensive calculator..
LEDs is series, or parallel, and any number.

PhilP
Phil, normally around 12 volts (3S Li-Ion) battery, but good for 4S, and my 18 VDC power pack. The red LEDs are slightly less bright, but I am content, nothing blows (darn that does it ;)), each ti their own if they understand the limitations.
 

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
29,504
3,053
Tamworth, Staffs.
Country flag
1k is a good 'safe' value (for the voltages we go up to) and you can always go down, a little, if you want to get more light out of them.

If you 'under-run' the LEDs, they will normally last longer..

PhilP
 

LGB333

Active Member
Country flag
Most of the LEDs (with resistors) I have seen are for 12 volts, and as I like to use duel colour (White/Red), I haven't seen any of these. As a rule of thumb, I use a 1kohm resistor, and this will light with 9 volts, and is good for 24 volts, I understand LEDs are current and not voltage dependant, but this is easier understood as voltage.
I use full track power output through the decoder for the 12v. LEDs with resistors I use and they work fine.
 

Greg Elmassian

Registered
8 Mar 2014
6,227
828
San Diego
www.elmassian.com
Country flag
At the voltages I use (24v) the current would be excessive, over 20 ma... but they are more rugged than they were 10 years ago.

I try to use efficient LEDs and find they are full brightness around 10 ma... so I use resistors calculated for that, and the forward voltage drop of the LED.
 

FatherMcD

Registered
13 Mar 2014
161
18
Idaho
Country
United-States
Country flag
At the voltages I use (24v) the current would be excessive, over 20 ma... but they are more rugged than they were 10 years ago.

I try to use efficient LEDs and find they are full brightness around 10 ma... so I use resistors calculated for that, and the forward voltage drop of the LED.
Greg, this question is posted as a reply to you as I got the information I used from your website. I bought some of the Supertex CL2 current regulators. I hooked up a flashing red and flashing orange LED in parallel and connected them to the CL2. (I took a chance with the parallel connection.) They are providing a great firebox flicker. Is anyone else using current regulators? I don't recall the price being excessive and it sure saved struggling with resistor calculations. Am I missing something that makes resistors superior to current regulators for LEDs?
 

Greg Elmassian

Registered
8 Mar 2014
6,227
828
San Diego
www.elmassian.com
Country flag
the current regulators are great, maybe they are making them in 10 ma now. I have about 100 on hand of the large cases and of the smd ones (for Z scale). I also have a stock of resistors, so often I will use resistors for my own stuff since I run 24 volts and will set the current the way I want. For people that have all kinds of voltages, the CL2 is the way to go, even if 20 ma is more that is necessary.
 

JimmyB

Semi-Retired; more time for trains.
Country flag
Greg, this question is posted as a reply to you as I got the information I used from your website. I bought some of the Supertex CL2 current regulators. I hooked up a flashing red and flashing orange LED in parallel and connected them to the CL2. (I took a chance with the parallel connection.) They are providing a great firebox flicker. Is anyone else using current regulators? I don't recall the price being excessive and it sure saved struggling with resistor calculations. Am I missing something that makes resistors superior to current regulators for LEDs?
So never having heard of CL2 (but then why should I have) and working out it did not mean Chlorine, I had a read on a number of articles, and have a number of points:
  • Why have 3 legs when only 2 are required.
  • If this is directional then it will not work with bi-colour (2 -leg) LEDs.
  • Some TD sheets inform that a resistor is still required.
Though to be honest most of the information was on Texas Instrument items as the Supertex items do not seem to be available in the UK.
 

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
29,504
3,053
Tamworth, Staffs.
Country flag

Greg Elmassian

Registered
8 Mar 2014
6,227
828
San Diego
www.elmassian.com
Country flag
PhilP, only 2 leads used.... 3rd is not connected.

Explanation here, along with link to data sheet:

Never seen a circuit where it NEEDS a resistor added, these run up to 90 volts input. I'd love a link to see what that is about.

Greg
 

LGB333

Active Member
Country flag
Hi Software Tools Hobbyist - Massoth recommends only using their Power Caps on their decoders. So I wouldn't try using that big old Capacity you removed from the locomotive. And normally for DCC operations, no PowerCaps/Capacitors are needed, unless you want to run also DC Analog power. But with two large motor block wheels sets on your locomotive, even DCC operations should be a problem traversing the plastic frogs in LGB track switches.
 

Greg Elmassian

Registered
8 Mar 2014
6,227
828
San Diego
www.elmassian.com
Country flag
Actually that cap looks like a 22,000 micro farad... or .022 Farad.... supercaps in the "keep alive" circuits are often several farads.... so it depends on what you want.... my guess it was there just to avoid resets of an old style decoder. Not needed on modern ones, unless you really have poor pickup problems and need it... in G scale usually it's only short 0-4-0 steamers or crappy locos that need a keep alive.

By the way, what does a keepalive have to do with Analog DC? Whether DCC or DC, the pickup issues would be the same.

Greg
 

LGB333

Active Member
Country flag
Actually that cap looks like a 22,000 micro farad... or .022 Farad.... supercaps in the "keep alive" circuits are often several farads.... so it depends on what you want.... my guess it was there just to avoid resets of an old style decoder. Not needed on modern ones, unless you really have poor pickup problems and need it... in G scale usually it's only short 0-4-0 steamers or crappy locos that need a keep alive.

By the way, what does a keepalive have to do with Analog DC? Whether DCC or DC, the pickup issues would be the same.

Greg
Greg - Your statement: "By the way, what does a keepalive have to do with Analog DC? Whether DCC or DC, the pickup issues would be the same." You're right on the track power pickup issue. But you're overlooking a key issue about sound systems. The major reason that decoder sound systems operating in DC Analog need keepalive capacitors is the sound board doesn't start operating until getting about 8 - 10 volts. Obviously on DCC layouts they're fully powered all the time, no issue. But on a DC Analog layout, the locomotive without a rechargeable battery or capacitor will start to move before the sound starts.............same when the locomotive comes to a slow stop. But with a capacitor installed, the operating or random sounds can continue for 20-30 seconds after the locomotive stops. So when I install a DCC/DC sound decoder into a customer's LGB locomotive and they only run DC Analog, I always recommend installation of the capacitors or rechargeable battery unit (Phoenix Sound).
 

Greg Elmassian

Registered
8 Mar 2014
6,227
828
San Diego
www.elmassian.com
Country flag
Oh, you mean a keepalive for the sound board, as opposed to the usualy nicad or nimih... got it... sorry... was focusing on the DCC decoder... I guess I have lost track of the direction of the thread. The OP bought a Massoth decoder, and I assume it has sound.

The last post by the OP was about a month ago, indicating he was working on a different project first.

Greg
 

Software Tools

Registered
18 Jan 2013
100
14
Sydney, Australia
Country flag
I'm finally getting back to work on RhB 202. I have a Massoth XLS (loosely) fitted and the basic drive functions are working well on analog and DCC.

CB7456D5-D187-4DCB-A308-1037CAB46F6C.jpeg

My next task is to get the lighting working, and after that fit a speaker for sound. I have none of the original LGB electronics for the loco, so will need to wire up the lights to the Massoth XLS. I have the sockets from the previous DCC bodge which will mate with the LGB 4 pin plugs from the lighting boards, but I have no information at all on the pinout for those plugs.

I know there are four LED lights on the PCB at each end of the loco, three headlights and one cab light. I assume that the two directional headlights connect to one pin, the headlight which is lit in both directions connects to another pin, the cab light also connects to one pin, and the remaining pin is the return for all the lights. Is that correct?

Does anyone have the pin out of the 4 pin plug for 2045 lighting, please?

9AC9B0E3-D0BB-4342-ACD0-3047BDD71F78.jpeg
 
Last edited:

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
29,504
3,053
Tamworth, Staffs.
Country flag
If you think they are LEDs, use a resistor, when testing..

If bulbs, set the voltage dividers before connecting. - They are probably 5V bulbs..

You can make both brighter, to your taste..
But only if you haven't blown them, to start with.

PhilP