West Exchange Sidings
Problems
This layout was designed with 4 NX panels, one in each corner. This makes operating the layout hard work, either a lot of walking or a lot of shouting. So it has been decided to go to a single panel operated by JMRI, with and optional front panel to operate the yard for shunting. This will involve replacing all the point controls so that they can be operated by DCC using a separate DCC power district.
The documentation for the current wiring is patchy.
There is an out of date list, written before the 24 Volt DC became AC, but seems to show the D connector wiring.
and an updated list, but some tag strips have move connections.
Where c/w is clockwise, cc/w counter clockwise.
Some notes written under the baseboards, such as the LMAB Xpressnet connections. From this information it looks as if the scenic boards may be wired differently to the fiddle yard boards, Better documentation is needed for fixing faults when taking the layout to a show.
Lastly the operation of some of the points using Seep point motors is at best patchy, those near the power supply working better than those at the other end of the layout. This clearly needs to be fixed.
Also, there has been an issue with bending of D connector pins. This could be due to trying to force 2 male D connectors together, in this case eliminating one set of connectors would help.
Solutions
The 2 short 3ft straight boards at the end of the layout are used for the test track,
so need local control as well as remote DCC control.
The plan is to use the current control switches on the top of the layout,
the single capacitor point CDU's will be replaced by the
MERG design dual capacitor design and a MERG DCC steady state decoder module.
The MERG CDU's need 24 Volt dc, so need a convertion of ac to dc.
MERG DCC steady state decoder.
Kit 53 firmware in C.
The fiddle yard points, 12 at each end, can be controlled
by 6 MERG pulse decoder modules, controlling 4 points each.
MERG DCC pulsed decoder.
The scenic front of the layout, has 7 points and one end and 8 at the other.
- One possiblity is to use the Cobalt IP point motors.
This would make the point movement quieter, but they are fairly expensive at £25 each,
18 for £450.
There is an issue with the address being forgotten. DCC Concepts reported "We did have a part batch of Cobalt Digital IP point motors that could suffer an address memory loss when a high voltage spike occured on the DCC bus. Most commonly as a result of a short, but in the case of some systems - when they are turned on/off.
A separate clean DCC power district may help with this. - Using the same MERG pulse decoder modules as the fiddle yard, with the current Seep point motors, will be slightly louder but only be £64. When they are back in stock. However, some points are on another baseboard, so using the steady state board and CDU's would be necessary for those points.
- A third alternative is to use small radio control servos. The small 9g servos are 20 for £24 each. The MERG servo mount is 6 for £4.53 each. The MERG 4 servo control board is £5.53 each. And the MERG DCC steady state decoder module, will drive 8 points for £14.60. For a total of £94 including postage. But we probably also need the servo setting box £16. and the servo turn on current can be excessive and will need some turn on delay for each group of 4 - 6 servos.
Power supply
Inside the box it looks like 2 x 160VA torroidal transformers, giving 4 outputs of 18 Volts at 4.44A. Each of these are connected to multiple pins on a D connector.
There is a Lenz command station and a booster. The wiring is a bit messy, there are a lot of short black wires. This needs redoing with slightly longer wires, and thicker for the DCC.
There are 10 fiddle yard tracks, 10 stationary trains at less than 100mA each, is less than 1 Amp. 6 running trains at less than 500mA is another 3 Amps. So the booster is probably not actually needed for running. What is needed is isolated power districts to allow some operation to continue when there is a derailment. We can have a switch so the fiddle yard DCC can be either from the command station or a booster.
The existing wiring on the end boards is a mess, so its probably best to remove most of the wires and replace with colour coded wires.
New Wiring
Each baseboard has 2 x 25 way D connectors, connected to a 36 way tag strip. So some connections are on 2 or 3 D pins to carry more current. It looks from the above list, as if the first 4 on each connector may have at least 2 pins.
The MERG CDU's take a short pulse of about 500mA to recharge, the pulse decoders only take about 30mA to recharge and 15mA normally. The CobaltIP's are 5mA and 40mA when moving. LED lights may be 10mA each. So after converting all the points to DCC operation, we can convert the power back to dc. This should then make the signal operation easier by having a fixed 0 Volt line. It should be possible to eliminate one of the 25 way D plug and sockets on some boards.
32/0.2 wire will have a resistance of 0.57 ohms for 100 feet, so fine for the DCC to the rails. 16/0.2 will be 1.14 ohms for 100 feet, so fine for 24 Volt dc which will only carry 1 Amp. 7/0.2 will be 2.6 ohms for 100 feet, so fine for the Xpressnet A and B, or the track section data. The wires to the 20 D connectors and D connectors will increase the resistance a little, 20 x 0.03 = 0.6 ohms, and the DCC pins have 2 or 3 pins in parallel.
The control DCC should come directly from the command station,
and be protected from any rail connection by MERG DCO's(District Cutout).
Kit 57, MERG DCO.
Tags 14 to 18 should be free, but they may not be. So first we need to free up those tags, then we can rewire while the layout remains operational.
| Tag | Desc. | Tag | Desc. | D pins | D pin Colours |
|---|---|---|---|---|---|
| 1 | DCC common, Black 32/0.2 | 19 | 3 pins | Black+Red, Black+Bue, Black | |
| 2 | Main DCC, Red 32/0.2 | 20 | (Booster DCC) | 2 pins | Red, Red+Brown |
| 3 | (ac) | 21 | (ac) | 2 pins | Blue, Green |
| 4 | (ac) | 22 | (ac) | 3 pins | Yellow, Yellow+Red, Yellow+Blue |
| 5 | (0 V) | 23 | (0 V) | 1 pin | White |
| 6 | 24 | 1 pin | Brown | ||
| 7 | 25 | 1 pin | Purple | ||
| 8 | (outer c/w stop) | 26 | (inner c/w stop) | 1 pin | Orange |
| 9 | (outer c/w appr) | 27 | (inner c/w appr) | 1 pin | Pink |
| 10 | 28 | 1 pin | Turquoise | ||
| 11 | 29 | 1 pin | Grey | ||
| 12 | (outer cc/w stop) | 30 | (inner cc/w stop) | 1 pin | Red+Blue |
| 13 | (outer cc/w appr) | 31 | (inner cc/w appr) | 1 pin | Green+Red |
| 14 | Xpressnet A, White TP 7/0.2 | 32 | 1 pin | White+Red | |
| 15 | Xpressnet B, Purple TP 7/0.2 | 33 | 1 pin | White+Blue | |
| 16 | DCC control, Green 16/0.2 | 34 | 1 pin | Orange+Blue | |
| 17 | 24 Volts DC, Pink 16/0.2 | 35 | 1 pin | White+Green | |
| 18 | 0 Volts DC M, Brown 16/0.2 | 36 | 2 pins | Orange+Green, Yellow+Green |
Things in ( ) might be moved or removed after rewiring.
Local Connections. 12 Volts for lights, Xpressnet L from 24 volt supply by regulator on each baseboard. Track sections, may be over a baseboard joint, and need a data bus to JMRI. Signal control connections, can use DCC control from JMRI.