ToT detectors.

For near 18 months I have played with the Linn Westcott "Magic Tee" bi directional detector (unlike the Roger Amos EDOTIS it will allow train operation when unpowered itself) but with a myriad of problems which arose at each turn. These included illumination through common paths without occupation, trains creeping away even when sat in an isolated section, illumination when track voltage rose above psu levels including when reversed. In all very dispiriting. The entire info read as if dual direction was the design parametre and that common rail working was the norm. Well, I have found that in order to obtain this set of requirements it is not possible to employ a standard reversing switch type controller and that all operations need to derive from a fixed polarity controlled source which is reversed after the ToT detection and fed into dedicated sections. The problems of excess control voltage were overcome using blocking diodes but these needed to be very carefully sited ( this also cured the creep problem). To obtain a uni directional output from the HM2000 I simply bypassed the reversing switch a fed the power out through the terminals associated with the extension units. Power for all this switching and detecting comes from an ex computer power unit which gives masses of current at 12, 5 & 3.3v ( this allows direct operation of LEDs from the 3.3v.) By the time the cost of the components have been totalled it begins to look expensive but when the little lights go on and off - well it looks worth it!

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Sailor
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