I'm attempting to use dual frequency LED's (red/green) to define the track polarity (train direction) but the nature of DCC pulse train has the LED's responding to both the positive and negative swing thereby allowing both LED's to partially activate and emit light. Is there a trick that could be used other than LED's to define the track polarity? I have a large layout with multiple loops (reverse and bi-level) and have a power control panel to control 17 seperate circuits but would like to have track indicators to verify the polarity sequence. Sorry for the lengthy question; any help would be appreciated Jim
Trick is that there is no "polarity" with DCC. You just have a north and south rail, but not positive or negative. I don't understand why you would need to keep track of the polarity anyway, since all the trains can run all over. Only reason I can see a "polarity" monitoring is on a reverse block if you're manually switching it, and then just have two single color LEDs, one for each direction, controlled by the same switch that controls the track. I use auto reversing circuits, so I don't have to worry about it.
Jim You say "dual frequency LED's". Do you actually mean the normal bi-colour/bi-directional LEDs across the supply lines (or the rails) with just a dropper resistor? Or do you have some other device with an AC component like a capacitor in there as well? If the latter, then you are probably getting the expected result as the LED will only see the AC signal. If the former, then as far as I know it ought to work - more info needed.
Hi Mike & Harron, Sorry for the confusion. DCC behaves as AC in some respects but being a pulsed DC signal (that never reaches 100% modulation on my MRC controller) I was trying to use the bi-color LED's to indicate track direction. I have many reversing loops plus 5 operating levels. When changing levels, I'm supposed to verify/change the correct track direction on the intended route. Auto reverse circuitry would be expensive for all 17 reversing situations although I might phase in the modules at frequent situations. In the mean time, the bi-color LED's favor one color when the modulation is above 50% or so, but I was looking for other options. Thanks, Jim
If you have the LED's in paralel to the curent, install a diode with each LED but reverse the polority of one of the diode. That way the pulse curent of AC will travel only one way in each LED
Dick & Co., I tried the reverse diode scheme but wasn't successful. I did find that by increasing the series load resistor (reducing the current) I was able to reduce them reverse diode light emmision without impacting the forward biased diode. The ideal load resistor is in the 6.8K ohm range. Thanks for your inputs. JIM
