Here is a link to install the NPN transistor to use the optical chuff.
http://www.mylargescale.com/Community/Forums/tabid/56/forumid/17/postid/6266/view/topic/Default.aspx
I've also tried a 2N2222A NPN and it worked about the same, if anything not quite as well as the Radio Shack one listed in the link above. Adding a 0.1 capacitor helped marginally.
I tried the DCC mode of the P5, but the K-27 is geared so high that even the slightest change in grade makes the chuff look strange. The P5 DCC chuff mode works off of the start voltage and then reads the speed step packets off of the rail. That is, the loco may be moving, slightly down hill with no chuff, or the chuff going and the loco is not moving slightly uphill. Add rolling stock and it's even worse.
http://www.mylargescale.com/Community/Forums/tabid/56/forumid/17/postid/6266/view/topic/Default.aspx
I've also tried a 2N2222A NPN and it worked about the same, if anything not quite as well as the Radio Shack one listed in the link above. Adding a 0.1 capacitor helped marginally.
I tried the DCC mode of the P5, but the K-27 is geared so high that even the slightest change in grade makes the chuff look strange. The P5 DCC chuff mode works off of the start voltage and then reads the speed step packets off of the rail. That is, the loco may be moving, slightly down hill with no chuff, or the chuff going and the loco is not moving slightly uphill. Add rolling stock and it's even worse.