it’s not clear that the way i think of or explain things is what you’re interested in. i hope you will read this lengthy note to better understand me and let me know,
let me know?
TazzyTazzy My thinking is that after you explain what something is / how it works, it’s always great to explain where things can go wrong and how to fix them.
yes, accurately, with clear and unambiguous statement
i can see a # of pages discussing problems that might be linked to from many other pages, hence they should be standalone or a sub-section within a page (<a name=)
TazzyTazzy For example: I’m not an electrical engineer, but for my WLED runs, placing a small resistor between my 3.3v->5.v logic chip that’s right next to the ESP32 devices and my first RGBW LED, really helps with reliability. I don’t need a scope to know that.
as an example of why i removed that section, the above statement is similarly not clear to me because it doesn’t explain the things it says. i’m guessing that the resistor between the 3.3 and 5V logic chips is between I/O pins. while i don’t doubt this makes things more reliable, it’s bad practice (open collector would be better). i also assume WLED means white LED. i assume this is not referring to resistors in series with LEDs driven by those chips either between the I/O pin and ground or the I/O pin and Vcc of the chip.
d
as for the Signal Quality section:
what’s the purpose of saying it’s a square wave, that any deviation is a problem? how much deviation?
the DCC Waveform page shows scope traces demonstrating ringing. Figure 5 shows ringing within the first several usec of the polarity change that can easily be filtered by the decoder. bear in mind it’s the same signal as in figure-4, just 50x faster. the processor is not going to be able to measure polarity reversals w/in a few usec
as for an explanation of ringing, why not reference the wiringFord site?
i don’t see the need for this statement – “Yet, the influence of the power bus and track, as well as the design of the booster present a number of challenges, such as distortion of the waveform.” how does this help the modeler?
in the following statement, the standard specifies requirements for the signal, not the hardware and doesn’t define degradation nor any limits – “The NMRA Standards include the requirement that both booster and multifunction decoder minimize any issues which may arise, such as the waveform quality at the booster output and requiring the decoder to accept a predetermined amount of signal degradation” i’m sure an economical implementation of the standard had been tested before the standard was proposed
i’d need to see some references to why variations in switching times increase distortion, why this might result in ringing and why termination would correct the design problem – Increasing the dead time between switching from one pair of transistors to the other comes with the possibility of increased distortion. Decreasing the period between switching can introduce ringing (overshoot) in the waveform." what can the modeler do about it?
there’s no explanation for the causes nor symptoms of distortion – “Distortion can include ringing[11] and switching (zero crossing) issues”. without some explanation this become “voodoo & mysticism” (i.e. gremlins)
ringing and spikes are 2 different issues, yet the following suggests ringing causes spikes – “ TN-9:2.2.1 Ringing is a distortion of the DCC signal where there is a spike at the leading edge of each pulse.” And what is TN 9:2.2.1 ?
no doubt there are spikes on the track as various locomotives draw power and intermittently loose contact or cause shorts when crossing gaps between power districts and reversing sections. but such spikes are intermittent
perhaps the section would be better title DCC Signal Corruption
