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FEZ control of DCC electronics


#1

As some of you may know, I’m into model trains. These days, most layouts are controlled by what are called Digital Command Control (DCC) systems. One of my “big dream” projects is to build such a system on a NETMF platform. The specs are all standardized by a governing organization called NMRA (national model railroad association). I’m currently in an extended “information gathering” phase of the project, and will be gleaning what information I can from the experts here.

My first question is to @ godefroi specifically. Would your opto-isolated 16 segment “relay” work with +/- 12V bipolar direct current? Take a look at http://www.dccwiki.com/DCC_Power for details of the power modern train layouts use. Almost all of the boards I’ve seen use opto-isolators for controlling various things in a layout, but the stuff is way overpriced IMHO.

BTW - I have searched high and low on the internet for NETMF controls like this and come up empty. There are one or two hobbyists who have had the same idea, but nothing has come of it so far.


#2

I’m absolutely unfamiliar with bipolar DC power, but it seems to me it’s simply square-wave AC instead of sine-wave AC.

I use PR26MF1xNSZ optotriacs, a.k.a. SSR, or “Solid State Relay”. They’re good for 120VAC, 600mA. Instead of moving metal contacts, the device uses a triac on the output side. I don’t have any idea whether this would work, but in the datasheet for the device, there is this:

I should probably be using a snubber circuit, but I’m dealing with low current and low voltage (24VAC), so I’ve so far been able to get away without one (and indeed, I didn’t find anything that looked like snubber circuits on any sprinkler controllers I disassembled).

I don’t know what effect the snubber would have on the DCC signal, because it seems to be transmitting data via frequency modulation over the power line. You’d have to try it.

Fortunately, the devices are only about $1.30 from DigiKey in ones, so you could probably afford to burn one or two.


#3

Correct.

and correct.

Thanks for the info. I’m also reverse engineering some DCC boards I already have, so after my “information gathering” phase, I’ll be moving into the “blue smoke experimentation” phase :slight_smile:


#4

@ ansomhall

This is a very cool project… looking forward to the videos :slight_smile:


#5

@ jasdev - This is a long term, keep me busy into (early) retirement, kind of project :slight_smile:

Funny… I am just loading up your fez connect web server for an “Internet of Things” remote control RGB LED demo early next month. http://vermontmakers.org . The screens render perfectly on my Android phone! Nice, nice!