Double-checking wiring for lights on an XLS......

[Zerogee]

This may well fall into the realms of "silly questions", because it's a pretty basic one that I'm 99% sure (well, OK, maybe 95%....) I already understand - BUT rather than get that tell-tale smell of frying electronics (not what you want on a Sunday, frying bacon is a much nicer smell....) I'd like to check first that folks here agree with what I think I understand.....

When wiring loco lighting to a Massoth XLS, am I right in thinking that the lighting function outputs (Li-V, Li-H and Li-I) actually switch to ground (0 volts) when activated - thus the actual lights are connected between the relevant function terminal and the +24 volts output, as shown in the XLS manual diagram (page 13 in the version I have to hand here). I'm doing an install where the loco lamps will all be conventional bulbs, so obviously polarity doesn't matter for them, BUT the interior lights of the coach part (it's a steam railcar) will be some pre-wired LED strips, which of course are polarity sensitive, so for those strips I wire the POSITIVE (red) wire of the LED strip to the +24v connection and the NEGATIVE (black) to the "Li-I" ("Licht Innen") connection?

What is throwing me just a little bit is that in the same diagram (p.13), it shows an LED (with resistor) connected between one of the other function outputs - in this case F5 - and the GND (Ground, 0v) terminal - thus implying that while the light functions switch to ground when activated, the other functions (F1-F5) all switch to +ve when activated....... is there any simple reason that they are set up opposite ways round?

Does that all make sense to anyone?

Jon.

 

[dunnyrail]

This may well fall into the realms of "silly questions", because it's a pretty basic one that I'm 99% sure (well, OK, maybe 95%....) I already understand - BUT rather than get that tell-tale smell of frying electronics (not what you want on a Sunday, frying bacon is a much nicer smell....) I'd like to check first that folks here agree with what I think I understand.....

When wiring loco lighting to a Massoth XLS, am I right in thinking that the lighting function outputs (Li-V, Li-H and Li-I) actually switch to ground (0 volts) when activated - thus the actual lights are connected between the relevant function terminal and the +24 volts output, as shown in the XLS manual diagram (page 13 in the version I have to hand here). I'm doing an install where the loco lamps will all be conventional bulbs, so obviously polarity doesn't matter for them, BUT the interior lights of the coach part (it's a steam railcar) will be some pre-wired LED strips, which of course are polarity sensitive, so for those strips I wire the POSITIVE (red) wire of the LED strip to the +24v connection and the NEGATIVE (black) to the "Li-I" ("Licht Innen") connection?

What is throwing me just a little bit is that in the same diagram (p.13), it shows an LED (with resistor) connected between one of the other function outputs - in this case F5 - and the GND (Ground, 0v) terminal - thus implying that while the light functions switch to ground when activated, the other functions (F1-F5) all switch to +ve when activated....... is there any simple reason that they are set up opposite ways round?

Does that all make sense to anyone?

Jon.

Sorry cannot answer the, but why not put a Blocking Diode in the circuit just in case you wire up the LED's the wrong way round? Good practice for LED's in any case.
JonD

 

[Deleted member 1986]

LI, LV, LH, A1, A2, A3 and A4 are shown as GND output functions, connect to POS to complete the circuit.

A5, A6. A7 and A8 are shown as POS output functions, connect to GND to complete the circuit

 

[Zerogee]

Thanks Arthur, that answers the question and agrees with what I thought was the case.
Much appreciated. I couldn't actually find that explained anywhere in the version of the XLS manual I have at hand here (from a version 1.4 decoder) the pics you posted give more info than the manual does! Are they taken from a newer version of the XLS manual?

I'm going to keep all the light outputs at full DCC track voltage (24v), I've put 24v bulbs in all the loco lights and my plan for the interior illumination LEDS is to take two of the 12v pre-wired 3-LED strips and connect them in SERIES (red wire on one strip to black on the other) then connect the remaining red and black wires of the series pair between the Dec +24v and the Li-I terminal...... any problems you can see with that?

Jon.

 

[Deleted member 1986]

Don't see why not, as long as each LED strip has -roughly- the same power consumption (current) at 12V. In that case 24V* across the 2 of them in series would be distributed fairly even.

Also if the current consumption at 12V differs too much, that 24V* would mean being be distributed unevenly. So you'd have the same current through each, but (for example) with one LED strip at 10V and the other at 14V. That is one strip would be too dim, the other strip would likely become overvolted and burn out.

*Should point out, that the Output voltage will be considerably less than 24 volts, depending on your Central Station and the decoder in use, the actual voltage measured between GND and + 22 volts might actually only be in the region of 20 volts.......

 

[Zerogee]

Thanks again Arthur - I've tested the two series-connected strips of LEDs on simple DC by putting the full whack (quoted as 22v) of a little LGB 1-amp 50080 powerpack through them, and they both light well with what appears to be equal (or very similar) brightness. Re the DCC setup, the old all-in-one Massoth 1200Z and an XLS decoder......

Jon.

 

[Deleted member 1986]

So far so good, only thing left that I'd do, would be with the decoder connected up and drawing power, would with a multimeter measure the voltage between GND and the +22, see what reading you get (this reading will be more or less what the LI output will provide, less any power consumption to other bulbs or led's) this will give you an indication as to will it be sufficient to drive the two led strips, if so, connect them up, and if they provide an acceptable level of brightness, then go for it!


Alternatively you may wish to use another Function, unfortunately A5 to A8 are not capable of driving the led strips, they are fixed at 5 volts and only capable of driving a 10 mA load...........

A5 to A8 whilst fixed at 5 volts can be boosted with a transistor to drive a higher mA load........should the need be required to swop things about..........and not to exceed 1.2 Amps the maximum function current of all outputs.

 

[Ralphmp]

Jon

For info, the latest versions of all the decoder manuals are on the Massoth Wiki site in PDF form. I tend to use these rather than the hard copies that ship with the decoders as I can zoom in on text and diagrams (my eyesight isn't what it once was!)