Lighting with a Digitrax 163 series decoder

[peteski]

I've seen ditchlights that alternate between bright and dim only. I believe some/many/most or all Amtrak P42's do or at least did at one time.

Fine, but with Digitrax and LEDs, that dimming is almost imperceivable to me.  It is more like a barely visible twitch.   

[tehachapifan]

While I've never seen their ditchlight effects in person, their gyralight seems about the same as Zimo's as far as dimming between flashes goes. Is this just an issue with the ditchlight effects?

[peteski]

While I've never seen their ditchlight effects in person, their gyralight seems about the same as Zimo's as far as dimming between flashes goes. Is this just an issue with the ditchlight effects?

I find all Digitrax lighting effect using white LEDs lacking fidelity.  We went as far as replacing the LED rotary beacon on friend's loco with a 1.5V incandescent micro bulb.  That makes the lighting effect much more realistic.  The thermal lag of the glowing wire filament, and its inefficiency in producing light, makes it more suited to be compatible with the light effects algorithms Digitrax uses.

[tehachapifan]

Right, which I believe is also the case with many/most/all(?) decoders. I believe even ESU states somewhere that incandescent bulbs produce better effects. The trade-off, of course, is the possibility of shorter bulb life. Still, I don't have any reservations about the gyralight realism I'm getting with LED's using Digitrax, ESU and Zimo decoders. The amount of dimming between flashes seems just right to me and I'm pretty darn particular about this stuff. Still curious if this is an issue with the ditchlight effects specifcally, or if there's something you may be doing differently in your installs somehow.

[peteski]

Still curious if this is an issue with the ditchlight effects specifcally, or if there's something you may be doing differently in your installs somehow.

There is nothing different with either mine or woodone's LED install. Function output - LED - resistor - common positive blue.  It is just that the decoder is not really designed to handle LEDs. No ifs or buts about it.

And yes, it is possible that the ditch light flashing pattern might be the worst example from all the other available effects.  Also, just like sound effects in models, this might be somewhat subjective and dependent on the person.

[GhengisKong]

They don't have LED mode, but they have couple of CVs for controlling the lighting FX parameters. The manual also recommends certain values for working with LEDs.  However, even in the latest generation 6 of the decoder (as in DZ126) I still find the effects lacking with LEDs. But they look great with incandescent lamps. Any other brand I tried handles LEDs much better.  TCS, ESU, ZIMO for example (especially the later two) have excellent control of the LED dimming (needed for those effects).

Sorry to bring out the dead, but are you using resistors with the incandescent lamps?

[peteski]

Sorry to bring out the dead, but are you using resistors with the incandescent lamps?

If 12V or 14V bulbs are used then no resistor is needed.  But sicne the common function positive lead (blue wire) is near the track voltage (around 12V) for 1.5V micro bulbs you will have to use a resistor.  To calculate the value you need to know the bulbs operating current.  It is usually mentioned on the packaging.  Probably something like 15 or 20mA.

Once you know that, then the resistor value can be calculated.   For example, if the bulb you were using is rated for 1.5V 15mA and the DCC track voltage is around 13V then the "blue" positive voltage will be around 12V.

We have:
Vs = 12V ("blue" supply voltage)
Vb = 1.5V  ("bulb operating voltage)
Ib = 15mA or 0.015A (bulb's operatign current)
Rx = resistance of the series connected resistor.

(Vs - Vb) / Ib  = Rx or (12-1.5) / 0.015 = 700 ohm.

The resistor power rating will be Rx * Ib² or 700 * 0.015² = 0.16W 

700 ohm is not a standard value, so use the next standard value of 750 ohms.  That will slightly reduce the bulb's current and brightness, but not much.  Resistor power rating should be larger than the above calculated value.  So a 1/4W resistor will work but might get a bit warm - a 1/2W resistor would be safer.

If your bulbs have different rating, just plug those values into the above equations. It is all just basic elementary school level math.