Multi-Channel Circuit Breaker

I started to do relay controlled blocks like you are doing. TMCC and DCS came along and all that became kind of irrelavent.

Adding a circuit breaker to each block controller sounds like an excellent idea. You can cut power to individual blocks while the rest of the layout continues to operate. That's great!

Will you have signals tied into the system or will it just be controlled behind the scenes? And are you intending this for conventional operation or as you mentioned Legacy; as in TMCC?

It uses a 40 pin PIC to monitor 14 current transformers and control 16 relays.  It also has the ability to monitor 5 status lines, which I plan to use to track switch positions.  In my layout two loops can be joined, so the blocks at the transition would function differently depending on how the loops were configured.  The extra two relays will control a boost/buck transformer for trestle ramps, depending on the train direction.  Of course, the status inputs can be used for any control input.

By legacy, I meant the old transformer-controlled trains.  (Postwar and MPC)  I don't have any new stuff with electronic controls other than my own electronic E-Unit.

Very good! I have learned, through this forum, that the old Post War stuff running under transformer control, is referred to as conventional operation. This is where my interests lie.

I'm planning on developing some block controllers with the Arduino microprocessor under conventional control. I'll be watching for more information about what you are doing. Please keep us posted. Thanks!

I considered the Arduino, but the PIC16F884 was just about a perfect match for what I wanted to do.  The digital I/O feeds 10-pin SIP headers for the 8-relay PCBs customarily used with Arduino.  I'm presently using surplus current transformers I picked up years ago, but there are some inexpensive ones available on eBay that should work fine too.  The current transformers are located remotely, and connect through a standard 16-pin header.

Firmware samples current multiple times on each positive half cycle and saves the peak current drawn.  That runs through a 4-AC cycle filter to ignore a single half-cycle glitch.  The result of that is compared with two limits, one to determine if a train is in that block, and the second to remove power if there is excessive current draw.  Right now the over-current is fixed at about 5A to avoid tripping on Trainmasters, but it could be made compliant based on what a particular train draws as it moves from block to block.

Even with the 4-AC cycle filter, the circuit should trip in less than .1 second if there is a short.  That could be reduced to under 20 mS if it seems too long, but I think that would make it too sensitive to single-cycle transients.

Jeff

 

Lionel's command evolution: TMCC/old, Legacy/new (& backwards compatible to TMCC) With all you'd spend on getting 14 blocks to automate, command control might be worth it. I use one. It drops voltage on train #A/block #1 until train #B reaches the end of block #2 and visa versa. The last tracks of the slowdown block are 100% dead as long as the voltage drop is active, just incase the volt-drop isn't quite slow enough. I had the relays, but just that would have $20-30 for two relays alone I bet (actually using I'm $65ea P&B industrial relays, but "freebees" from HVAC work)

Actually the block control is very inexpensive.  PCBs with eight 10 amp relays only cost about $6.  I can't build them for that.  They are not P&B quality, are fine for this application.  The PIC, components, and PCB cost another $40.  So block control including a circuit breaker function for 14 blocks cost me about $50.  (If I didn't already have the current transformers, they would have added another $15.)  I have well over a dozen postwar and MPC engines that would cost MUCH more than that to upgrade or replace.

So are you programming the PIC in assembly language or is it some other compiler? Just curious.

I've been programming in assembly since the 8080 / 6800 era.  I have used compilers for other applications, but this is straight assembly.

Just an update on this.  The prototype is working with an individual circuit breaker function on each of the 14 blocks, and block control keeping a low power block between trains.  The circuit breaker remains tripped until reset manually.