Turnout Control – Update

The turnout control I described in my last post was working great… That is until I subsequently added block detection to the mixture.

I am using RR-CirKits equipment to access the Loconet buss of my Digitrax system. I am using BOD-8 block detectors, connected in this case, to a TowerMan input-output unit. I had originally planned to use a TC Mark 64 for this test, but my mountain/helix did not require many inputs and outputs so I used the TowerMan I had for this area. The BOD-8 uses 8 inputs, there is another 8 inputs available for the three capacitive touch switches used for local control of the turnouts and any other sensors I might need.

When I connected the block detection equipment, I found that some of my blocks were showing as continuously occupied. I scratched my head for a couple of hours before I realized that the blocks that were giving me trouble had turnouts controlled by my home-built Arduino based accessory decoders. I could not figure out the problem until I reached out to Geoff Bunza thru Railroad Hobbyist Magazine. He developed some of the circuitry that I’m using in my turnout decoders.

This incorrect circuit has the detection circuit as part of the buss feed passing through the CT coil

After a couple of emails back and forth, he finally got across to me what the problem was. The DCC decoder circuit could not be included in the block detection feed through the CT coil.

This is the correction Geoff suggested

So after making a couple of modifications to the decoder to separate the DCC decoding circuit from the DCC feed to the turnout frog, the thing now works as planned. Putting it all together, it looks something like this…

Detection and Turnout control combined schematic

I now have seven detection blocks and three turnouts working with this system and it looks like a success, so far. I’ve even set up a JMRI panel to test that functionality. Switch control and block sensors work as expected. One thing I don’t like about the arrangement is having turnouts as part of the block. I may want to make them separate blocks because you cannot tell when a train clears the points in JMRI. I’ll use it for a while, it may not prove to be an issue in operation.

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