Zorcan Posted June 23, 2021 Share Posted June 23, 2021 Does anyone understand why these devices provide such a long run-time in the absence of the DCC track power? I have opened one up and can see that the circuit is more complex than the "traditional" one I am familiar with - of Capacitor(s), diode and resistor. It contains 6 off 0.47uF 2.7 volt capacitors in series. There also appears to be a resistor ladder, with each capacitor connected in parallel to one of these resistors - I take it that this is to ensure an equal/controlled voltage (and therefore charge) for each capacitor. There are also several other components which I cannot identify - nor is it clear as to how they are interconnected. The most powerful devices I have made contain 3 off 0.47uF 5.5 volt capacitors in series. In principle, therefore, my device should provide twice the endurance of the DCC Concepts device. In fact, I get less than 1 second of running after the track power is lost, whereas the DCC device runs a loco for several seconds. I would appreciate any insight anyone can add. Link to post Share on other sites More sharing options...
Ron Ron Ron Posted June 23, 2021 Share Posted June 23, 2021 Not an explanation of how it works, but videos showing other brands of stay alive, with a longer run time. TCS Lenz USP (with the clever reversing trick) Link to post Share on other sites More sharing options...
RMweb Premium ColinK Posted June 24, 2021 RMweb Premium Share Posted June 24, 2021 On the Lenz video, the loco changes direction, but how does it receive the DCC signal to do that if it is isolated from the track? 1 Link to post Share on other sites More sharing options...
Porcy Mane Posted June 24, 2021 Share Posted June 24, 2021 (edited) 19 minutes ago, ColinK said: On the Lenz video, the loco changes direction, but how does it receive the DCC signal to do that if it is isolated from the track? The command to change direction received whilst on the live track. Deceleration and acceleration curves programmed into the chip. Stay alive does its normal job in fooling chip into thinking it's still on live track. Edited June 24, 2021 by Porcy Mane 1 Link to post Share on other sites More sharing options...
Ron Ron Ron Posted June 24, 2021 Share Posted June 24, 2021 23 minutes ago, Porcy Mane said: The command to change direction received whilst on the live track. .... Can't be the case, because you can send commands whilst on the insulated section. 1 Link to post Share on other sites More sharing options...
Nigelcliffe Posted June 24, 2021 Share Posted June 24, 2021 46 minutes ago, ColinK said: On the Lenz video, the loco changes direction, but how does it receive the DCC signal to do that if it is isolated from the track? Lenz, being Lenz, came up with something a bit different to most others. Very very approximately like this: Its a capacitance trick. With the rails being close by (piece of paper away, or bit of rail dirt), there is a little bit of the DCC signal available due to capacitance effects over the thin insulation layer. So the decoder can sense the DCC signal, even though it cannot receive the DCC power. Consequently, the decoder can still receive decoder instructions and respond provided it has power from another source (the capacitor). It also means the decoder can tell the loco is off the track, and stop (ie. the decoder won't run the loco over the scenery, unlike some other very simple high capacitance designs). The capacitor is also a low-voltage item, with a voltage multiplier to interface it to the DCC track voltages. 1 1 Link to post Share on other sites More sharing options...
Ron Ron Ron Posted June 24, 2021 Share Posted June 24, 2021 5 minutes ago, Nigelcliffe said: ......So the decoder can sense the DCC signal, even though it cannot receive the DCC power........... Indeed. Just to add to that... DCC is a communication signal technology (a version of Bipolar DC encoding). The motive power is effectively just a byproduct of the signal transmission mechanism. So, as Nigel says, the signal is getting through the paper, but with a much reduced amplitude (effectively just RF), which is not enough (i.e. zero power) for a decoder to extract any motive power out of the signal. .....sort of ! . 1 Link to post Share on other sites More sharing options...
Porcy Mane Posted June 24, 2021 Share Posted June 24, 2021 1 hour ago, Ron Ron Ron said: Can't be the case, because you can send commands whilst on the insulated section. 1 hour ago, Nigelcliffe said: Lenz, being Lenz, came up with something a bit different to most others. Very very approximately like this: And there you have it. Thanks Nigel. 1 Link to post Share on other sites More sharing options...
Zorcan Posted June 24, 2021 Author Share Posted June 24, 2021 So . . . no one out there understands how the DCC Concepts device performs so much better than a "Conventional" capacitor/diode/resistor device? Link to post Share on other sites More sharing options...
Crosland Posted June 24, 2021 Share Posted June 24, 2021 1 hour ago, Zorcan said: So . . . no one out there understands how the DCC Concepts device performs so much better than a "Conventional" capacitor/diode/resistor device? Almost certainly they use supercaps which are 0.47F NOT 0.47uF. Six in series gives 0.078F or 78,000uF. The resistors are, indeed, for charge balancing and also help discharge the caps when not in use. Link to post Share on other sites More sharing options...
dpgibbons Posted June 24, 2021 Share Posted June 24, 2021 Some guidance on supercap charging circuit designs here Link to post Share on other sites More sharing options...
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