Decoder
Tester The Loy’s Toys (now Ulrich Models) unit is the first decoder tester I used. Ulrich offers ad- ditional harnesses and a motor to use with its newer version. It still works but has been made obsolete by newer testers.
does not cover this. Around 2001, the
NMRA Standard recom- mended implementing CV11, packet time-out value. If implemented, the value in CV11 is the maximum time period the decoder will main- tain its speed without receiving a valid packet. After reaching the time out, the motor output is turned off. There is no requirement for re- setting the function out- puts. If CV11 is 0, the decoder is not reset. In either case, many manufacturers have not
effects. I turned off analog con- version on the decoders and ac- tivated the wanted outputs with a DCC system. I then switched the power source to a 12 VDC supply.
Tam Valley
Booster This is the Tam Valley 3-amp booster I use for testing DCC decoders. The 3-amp capability is more than enough to test and program even the most stubborn de- coders.
I had mixed results that de- pended on the manufacturer. Some maintained their states on DC until power was turned off. The decoder then resets itself the next time power was applied. Oth- ers turned off motor outputs, but the function outputs remained on when switched to DC. On still others, both the function outputs and motors turned off. One example is a Digitrax DH123. If a function output was on and the motor output at a set voltage, when the decoder was switched to DC, all outputs were maintained. If the decoder was then powered down and re- powered with 12 VDC, the previ- ously enabled outputs remained on with the same lighting ef- fect. The motor output, however, turned off. DC power could be cycled multiple times with the function outputs continuing to operate. This led me to investigate NMRA DCC Standard S9.2. I wanted to see if it specified how decoders would function when being switched from DCC to DC. What I found is the Standard
64 RAILROAD MODEL CRAFTSMAN
implemented the packet time-out value, CV11. Even if they have, it is unclear if the decoder reset cov- ers the decoder function outputs. (See NMRA Standards 9.2.2 and 9.2.4 Section C for more information.)
Implementation My early work proved it is dif-
ficult or impossible to predict how a decoder will act on when switched from a DCC system to a
locomotive power and the upset of track shorts. My initial thought was to use an economical (cheap!) stand- alone DCC system to power these recycled decoders. This approach typically leads to a different man- ufacturer with another learning curve. The second option was to use a separate DCC booster for pow- ering the decoders. Unless you are fortunate to find a good deal, this is a relatively expensive alter- native ($100–200).
After research, I identified a less expensive option, a Tam Val- ley 3 amp DCC Accessory Boost- er, Model DAB002, that sells for $49.95 and requires a separate power supply. While the booster is advertised as a 5-amp unit, its continuous rating is 3 amps, trip- ping at 5 amps. Tam Valley rec- ommends the board be well ven- tilated if you are going to operate at 3 amps for a long time. I used an older 12 VDC sur- plus power supply on hand. Many of the electronic supply houses carry these inexpensively (less than $20). A Google search for 12 VDC, 3–5 amp power supply will
DC power supply that is powered on and off. What’s needed is an economical way to maintain the DCC commands to the decoder without the limitation of robbing
locate many sources. A feature mentioned in the
Tam Valley manual keeps the new accessory bus up for five min- utes if the DCC Command sta-
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100