Flickering normally occurs if the function/lamp return goes to chassis, which is the same as rail ponential, but not the same as decoder ground.

In this case lamps will be on when the digital signal is -20 V, and (near) off when it is +20V. So what decides the amount of flickering is how much of the time the digital signal is +20V.

If you run Delta with only one Loco, the digital signal stays -20 V most of the time; therefore you might not notice the flickering. With more locos, DCC signals (as in Intellibox) and other signals as mfx, the flickering might be more noticable.

Rectifying and using a capacitator will work; but AFAIK also using double diodes on the return of the lamps, so that current may flow from either the wheels or the slider (Yes, what is called function return, actually feeds the lamps with current; the + and - are switched from what you expect).

/Lars

Hallo guys,

yes, that was my question.
and yes, Rudy and Lars:
I think you are right:
that the Delta Control
and the 6021 (with the old Motorola)
stays at -20 Volts most of the time.
That explains the flickering with the MS.

This all means, of course, to
avoid flickering lights,
that all the lights and led's
should be off of ground.
Return with the orange wire.

Greetings
Bill

sorry if I go a little off-topic. It happens to me to have lights that flicker in intensity (they don't turn off completely!) approx. twice in a second with an Uhl 76220 decoder. It happens both with lightbulbs and LEDs. Someone knows why?

Thank you!

Hi Hans, others,

That all sound sensible. Let me try to add one or two things.

- Indeed, the diodes might be a bit slow with signals that change polarity as often as the protocol in question does. So it might be a good idea to use fast diodes, such as Schottky ones (I think used the 1N5819 or BS130 for this, though I not sure anymore).

- Use bridge rectifiers where possible. This may be, however, less practical when lighting sets of coaches that are connected by conductive couplers. At least, I usually try to have ground pickups installed in several cars, to improve contact. (Trick: one could still do that by having a full bridge rectifier in the car that has the pickup shoe, and half a bridge rectifier in each car….)

- Again, adding capacitors and possible the use of voltage regulators (eg. 7812) can further help. Indeed, I work on a current coach lighting project that I hope to report on later on, that uses that (plus other things) in very car.

Still, there are things I do not understand. I use digital braking sections in my layout. These are fed by negative DC, generated by a single rectifier (using a fast Schottky diode) plus a 470 uF capacitor. (using a bridge rectifier here is impossible as the braking section shares the same return rail as the rest of the layout). But I noticed that lighted coaches in that braking section still flicker! I hope to have time soon to study the signal on that section. Is the capacitor too small? I would tend to doubt that, given the short periods of the signals.

Of course, I could always add another ‘perfect’ DC power supply to feed just the braking sections. For a few bucks you can but a 13.8 V regulated ‘lab power supply’ of more than sufficient power. (In fact, I have thought of doing this before just to reduce the power draw on the main line as on average more than half of the power consumers such as lighted coaches are in braking areas, not actually running).

But I would prefer to find out why the flickering is there in the first place!

I’ll keep you updated of my findings, and appreciate other people’s ideas and observations.

Finally, it would be nice to find out the exact signals generated by the various controllers (6021, Delta, Delta 4f, MS, CS). What are their silent periods when there are no new commands? And how is their ratio between + and – in different situations? Some people suggested that once you have many locomotives in use, the signal will be more often positive than with a single train. I’m not sure. As long as there are no new commands to be sent to loco’s, would there be any difference? Does the system actually repeat messages at regular intervals to all trains? Or does it just send out a message with no real content after a time out? To find out more, we would either need a good description of the protocol or its implementations in the various devices, and/pr somebody doing some measurements with a sampling oscilloscope. I know that these days, sampling or memory oscilloscopes on the basis of a PC are rather affordable, but I do not want to buy one just for this single measurement ;-)

Sorry for the much too long mail (no, I am not bored, I do have other things to do - oo many in fact!!!)

cheers rudi

Well, the decoder in the loco's is already fine. When connected properly, the head lights of loco's do not flicker at all.

The problem is more when you have lights installed in coaches and so on. Maybe we could convince M* to develop more advanced, nonflickering light sets. But that will very likely result in higher prices, and it might be difficult to adapt that to different coaches. So here their might be some work for us, hobbyists.

I would definately appreciate it, however, if M* would start putting conductive couplers on all its loco's. However, to have non-flickering lights, it would be necessary to have two-conductor couplers and M* just added a single conductor coupler to its program....

...

Thank you for your answers. But can I use a "normal" electrolitic capacitor, (since the current in the lights there is a digital signal, so it's AC) or I have to insert 2 capacitors in anti-parallel to prevent damages?

Any wiering diagram for this Rudi ?

Anyone now what light kits I should have for the ser 42281 ? (MHI '02)

It couldn't help better! Thank you very much, Rudi!

Hi to all!

On my layout I tested today
with the MS and the Delta Control 6604:
the flickering was definitely more less with
the Delta Control , almost nothing!

I use the MS on a digital layout with C rail.
On my great layout with K-rail
I use the Delta and with rectified AC transformer
i.e. analog.

Greetings
Bill