When using a 220uF or possibly a 470uF capacitor no other parts are really required for “simple” loco con-trol; although installing a choke coil (100 mH / 100 mA, available from ZIMO) is recommended in the posi-tive wire to guarantee that the decoder can be updated with the update module MXDECUP and that the ZIMO loco number identification works.If larger capacitors are used, which is actually a good idea, extra circuitry is required. The condenser is re-charged through the 100 ohm resistor. This is to prevent a shut down of the command station during start-up. If a large number of loco’s so equipped are on the layout the command station could interpret the current flow to these capacitors as a short circuit. The diode (e.g. 1N4007) is required to bypass the resistor when power is needed by the decoder.NOTE: If signal stops by “asymmetrical DCC signal” (= Lenz ABC, implemented in ZIMO decoders early 2005) is employed, the resistor-diode combination is necessary in any case (even when using small capaci-tors) to ensure that the decoder can detect the asymmetry of the signal!The purpose of the resistor 3K3 shown in the drawing above (not required in all cases) is: even though a large condenser supplies the motor and lights for just a few tenths of a second (1000uF) or a few seconds (e.g. 4700uF) the remaining power, although at a voltage level below what is required by the motor and lights, is sufficient power to keep the decoders memory alive for quite some time (several min-utes). This is sometimes a rather undesired effect. For example: If a running loco is taken from the track and the speed then set to zero, the loco would briefly run at the previous speed when it is set back on the track after about a minute. Using the above-mentioned resistor would erase the memory after just a few seconds.
Print
