OK, I've only done this on one session, but it was very repeatable at the time. Hardware: Arduino UNO Pololu MC33926 driver Test track directly wired to the Pololu OR Main layout wired to Pololu through a Digitrax PM42 When operated with my Digitrax Zephyr Xtra, the main layout (which aside from the 4 power districts has no oddities - no reverse loops, etc.) works normally. When operated on the test track, the DCC++ Base Station works just fine. When I connect the Base Station to the input feed to the PM42 and fire it up, any locos on the track do the "Shoot off like a cannon" thing that dual-enabled DCC locos tend to do when exposed to a bad DCC signal. My supposition, of course, is that there's some kind of funky interaction between the PM42 and the Pololu board that is screwing with the track signal timings and causing the locos to freak out. Aside from the sheer size of the track attached (10x10 room sized single deck vs. 4 or 5 straight pieces of Unitrack), I don't know what else is different. Have any of you seen this behavior? Any suggestions? I do plan to bypass the PM42 and see what happens, but that's going to take some effort to get at the right wires.
Mark, I saw this happen when I first set up DCC++ a year ago. If I remember correctly it was because I inadvertently had a four cable wire bundle that had the negative ground wires crossed in it. The -neg programming wire was crossed and used with the +pos main track wire. The -neg main wire was crossed and used with the +pos programming wire. The result was the Engines took off like a bat out of hell. Maybe you have a - negative current crossing and interacting with an incompatible +positive DCC signal. Just an observational guess..... Kevin
If I get this correctly, the MD board is connected to the input(s) of the PM42, which is driven by a DCC++ system..... The PM42 SHOULD be completely transparent to the DCC signals, and only be monitoring the current draw to each district. So, with the PM42 not in use, how are throttles connected? Have you tried to run the layout with the PM42 but no loconet connected to the PM42? I think there's a conflict between the loconet and DCC++ in the PM42....... I don't use any digitrax stuff, but the PM42 manual says it'll work without loconet. Just trying to talk you through some steps you might have skipped.....I find that talking to someone(anyone in fact) slows my thought processes down enough to explain stuff to that person, so that I see issues that I skipped. Good Luck....keep us informed.
Low priority... I'll get back to it soon... I did notice that I had accidentally unplugged the power to the PM42 (the separate 12V logic power, that is). Don't know if that matters, but it's something else to check.
