I am working on my own dcc decoder of sorts and I am debating whether to go with the 8-pin or the 9-pin harness.For my first test train I bought an affordable HO Athearn GP60M "ready to roll" and I started designing for the 9-pin. I realized this train doesn't have ditchlights and I'd like to be able to test that aspect (I want to test my board controlling 4 lights). I started looking for Athearn "Ready to Rolls" with ditchlights, and it seemed the price jumped up quite a bit.I probably need to buy a number of test locomotives (with perhaps different 4 light setups). I've seen Katos and Bachmanns (that I believe use 8-pin) that might be cheaper 4-light test units.Any solid advice on whether I should go with the 9-pin or 8 pin harness on my circuit board? Controlling 4 lights (rather than 2) is one thing I'm looking for.Does one of these or the other (8-pin vs 9 pin) have a larger marketshare in the DCC-Ready locomotives?
Information provided by ESU tends to indicate that both the 8-pin and 9-pin sockets are on their way out in favor of a 21-pin socket developed in Germany. The switchover in the U.S. may be some years off, yet.
The 9-pin JST header on some Digitrax, NCE, Tsunami, and other decoders only provides one more function wire that what is available with the 8-pin NMRA socket, but takes up less room. Most Athearn RTR and Genesis locomotives have provision for both on the same board.
If you don't already have a locomotive with one of these boards, you can order it as a spare part from Athearn. The biggest drawback to Athearn's board design is the way it clips to the top of the motor. Many of them fit too loosely for reliable contact.
Of the two, the 9 pin is more versatile. It can connect to locos that have 9 pin connectors, plus there are any number of harnesses made that are 9 pin on one end and 8 pin or some other arrangment on the other.
You don;t need a loco - you can build a decoder tester, which more or less is a loco simulator. A motor, and a bunch of LEDs with resistors to be the headlights, ditch lights, and warning beacons. Hook your decoder to this and connect the track input wires to the track connections on the DCC system, and off you go. You can incorporate up to the typical maximum of 6 functions plus the motor. Anything over 4 functions requires more wires than the 9 pin connector handles, though.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Great. Sounds like I'll go with the 9-pin. Thank you very much.