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Block Watcher Calibration

Posted by on Feb 18, 2016 in Tips DCC Components, Tony's Tips |

Hi Guys, I have DCC Specialties Block Watchers on my large home layout, hooked up to a signal system, and I’m using NCE as my DCC system. I have all my cabooses equipped with resistor wheelsets so a block is detected as occupied when any part of a train is in it.  I’ve had no problems for several years.

Recently, two of the Block Watchers stopped detecting the cabooses, but still detect the locomotives when in the block.  One Block Watcher needs an extra 1000 ohms to detect; I can change the resistance of the caboose wheelsets to compensate.  But the other Block Watcher needs 7000 ohms more resistance to detect the caboose in the block.

How do I adjust the Block Watcher to detect a lower the level of resistance?  I know there is cv54 & cv55 that can be programmed, but I would like your advice before I try anything.  I do not want to risk changing things that might make it worse.  Otherwise, my eight Block Watchers and nine PSX circuit breakers and PSX-AR circuit breaker/auto reversers have worked flawlessly.

Thanks—- Bob M

Bob: There are two things to try.

  1. First, with power off and nothing in the block, move the program jumper to connect J3-2 to J3-3 (center two pins).
  2. Turn on power and you will see D4 flash for a bit.
  3. When it stops flashing, turn off power and restore the J3 jumper to J3-3 and J3-4. This will calibrate the current to your layout.
  4. If this does not solve the problem, place the BW in program mode, (J3-1 connected to J3-2) and set CV63=42. This will restore all settings to the factory default.

What value are you using for resistor wheels on the caboose? The ideal is 3.3K, but the BW will work with higher values. The other issue is to check your track voltage. If it has dropped, it will also cause a reduction in the sense current. Voltage drop can be caused by a bad connection into the block. You want to check the block voltage when the block is occupied to make sure there is no significant loss of voltage when current is drawn in the block. A drop of a volt or so is normal, but you should not see much more than that. Ideally, the block voltage should be 14.25 to 14.5 volts.

Block Watcher Manual
Block Watcher Review