Acknowledge Detector Variant 2

This circuit can be used for detection of Basic Acknowledgments from a Digital Command Control (DCC) Decoder following NMRA RP9.2.3 (Service Mode). It can be used together with (or to modify) DCC-MB or TMWDCC.

(ACKDET02.GIF)

Notes

• You can invert the output signal by exchanging the inputs of IC1A (you have use a knife and some wire)
• If you don´t need an optocoupler between the track and the PC remove R1 and connect IC1A,2 direct to U10A,1
• I have tested this circuit with a Digitrax DH84G Decoder and a current-limiting-resistor (Resistor R1 of the TMW4 board) of 120Ohms. The Voltage at the track has been approximately 15V. It drops to approximately 3V when the decoder gives the acknowledge pulse. A pulse of 28mV and 2.5ms can then be measured over R3. This gives an high-level-pulse of approximately 2ms at the input of U10A. With TMWDCC (Version 1.11) I have successfully read back values form the decoder.

ACKNOWLEDGE DETECTOR 1
BACK TO DCC
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© 1997 by Martin Pischky (martin@pischky.de)
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