To implement signaling on my layout I first need to be able to be able to detect block occupancy. So my next project has been a LocoNet Block Occupancy Detector. I decided to make a 16-way device as that made efficient use of the available I/O pins on a 28-pin Atmel ATMega88/168 device. A while ago, I managed to get about a 100 of the VT-5 Current Transformers. These have been used by others to make block occupancy detectors, based on Rob Paisley's - Block Occupancy Detector For DCC.
Initial tests show the detector to be reasonably sensitive and able to detect a 5k - 10k resistive load with 1 turn of the track feed wire through the current transformer. With 2 turns, it was able to detect a 20k (2 x 10k) resistor and even just my finders across the track. However, with 2 turns, when I applied a short to the first block the second block also triggered. This is probably due to how I have mounted the current transformers, which is convenient for mounting on Veroboard because of the way the copper tracks run, but not good in keeping the magnetic flux from one transformer from being detected by adjacent current transformers under heavy loads - oh well that's what prototypes are for...
Completed LocoBOD-16 prototype
Top of the Veroboard showing links and component placement
Underneath showing cuts in the copper tracks
Close-ups of the components for each current transformer input
Close-ups of the components for each current transformer input
Close-up showing the link under the IC socket linking the two GND pins
Site hosted by: