you may want to check that you don't have 'zero bit stretching' turned on ...especially if the zero is only emphasized on one half of the waveform ..
the length [650ms] is within spec for the zero bit,
mbarrettThe 60 and 120 microsecond pulses are no surprise. The 650 microseconds are a surprise as I understand the DCC waveform will fill out with "do nothing" pulse messages (of continuous 60 and 120 microsecond pulses) if there is no "message" to send. Are these longer pulses an anomaly with the DB150?
Are these longer pulses an anomaly with the DB150?
the preamble (line 20) for a packet is 14 "1"s. So when a packet is not being sent, a random sequence of "1" (~55-60 usec) and "0"s (>= 100 usec) can be sent.
it wouldn't surpise me that if the processor got busy for various reasons, it just sent a "0" for much longer that 100 usec and < 12 msec (S-9.1 lines 19-24).
so a 650 usec pulse is within spec as a "0".
greg - Philadelphia & Reading / Reading
SPSOT fan First, to the MR forums! Second, I will admit I understood about 15% of you post. However from what I do understand it seems your trains run fine, so you really don’t need to worry about anything. It seems your using some tool I’ve never heard of to measure the signals your DCC system is sending out, and you’ve found some irregularity. First you’ve got to figure out what pulses of 650 microseconds do. I don’t know the answers, but I bet someone here does and if they don’t, consult your manual. Hope this was helpful!
First, to the MR forums!
Second, I will admit I understood about 15% of you post. However from what I do understand it seems your trains run fine, so you really don’t need to worry about anything. It seems your using some tool I’ve never heard of to measure the signals your DCC system is sending out, and you’ve found some irregularity.
First you’ve got to figure out what pulses of 650 microseconds do. I don’t know the answers, but I bet someone here does and if they don’t, consult your manual.
Hope this was helpful!
A very common test instrument. Probably an add on to convert a smartphone today. I use to have a solid state digital version.
My best was a Tek465B when I worked for NASA.
https://en.wikipedia.org/wiki/Oscilloscope
Edit.
I just searched. D.I.Y. Or buy one but really not needed unless you are curious. IOS or Android.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-9.1_electrical_standards_2006.pdf
https://www.nmra.org/sites/default/files/s-92-2004-07.pdf
Found under: https://www.nmra.org/index-nmra-standards-and-recommended-practices
Gary
Regards, Isaac
I model my railroad and you model yours! I model my way and you model yours!
Is it possible that you used address 0 to run DC engines, and what you are seeing is zero-stretching?
Welcome.
What does the NMRA say?
If the locos run fine, no big deal. Run your trains.
I looked with my Tek 465 some years ago. Interesting.
I use the NCE Power Cab. No zero stretching.
My Digitrax DB150 Command/Booster drives trains as expected. However I am examining the DCC waveform with an oscilloscope and am surprised to find a waveform of 60 microsecond, 120 microsecond and 650 microsecond pulses.
The 60 and 120 microsecond pulses are no surprise. The 650 microseconds are a surprise as I understand the DCC waveform will fill out with "do nothing" pulse messages (of continuous 60 and 120 microsecond pulses) if there is no "message" to send.
When the track power is first turned on at the throttle, a continuous burst of the mixed short pulses occurs for 4 seconds. Then the 650 microsecond pulses enter the wave train, mixed in (seemingly randomly) with the shorter pulses. The longer pulses occupy about 50% of the overall pulse train duration.
Are these longer pulses an anomaly with the DB150? They do not seem to affect control of the (one or two) simultaneously operating locomotives.
MichaelB