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DCC & Control

I had already invested in a Lenz Set 100 system for my previous layout. This was transferred but a number of improvements have been made. The main DCC output goes via a power meter to a EB3 block isolator which divides the layout into three zones. This should mean that if there is a short only a part of the layout is affected but it has actually given more trouble than it is worth as it is too sensitive to transient shorts and it is now bypassed. All points are controlled by DCC using Lenz or MERG decoders and the layout is divided into a number of sections which are sensed using Lenz or LDT detectors which feed back via the RS bus. All of this is then controlled via custom control software that I have written. The software has been designed to be controlled via a USB switch panel but recently I have switched to a touchscreen for control which is far more intuitive. There are also a number of video cameras in the fiddle yard and these are shown on a separate monitor via a quad display. The following block diagram shows the main features of the control system.


Block diagram of Control System


The power bus is made from a double twisted pair of 22AWG wire with droppers also from 22AWG wire. There is at least one dropper to each section of track. A number of sections of the layout have detection fitted using either Lenz or LDT units, thus adding significantly to the number of droppers required. All the signal wiring is done via multicore cables and krone termination blocks. Unlike the previous layout, these are mounted on a wall below the layout making access easier. There is an additional safety feature in that the access bridge has a microswitch linked to the Lenz emergency stop input which will stop all movements if the bridge is opened.


Under the baseboard showing the most complex area of DCC wiring with the detectors for the fiddle yard The signal wiring Krone frame. The shelf housing the PSUs and Lenz 100 is on the left


The control software is written in Visual Basic 6. As well as showing occupancy it can set routes by clicking a start and end location. This then sends instructions via the Lenz system to accessory decoders (MERG and some Lenz) which drive SEEP or Peco point motors fed froma 16v AC supply. By knowing about set routes and occupancy the software can also automatically control the signals. These are driven via MERG steady state decoders and relays. Two DCC addresses are used per signal - one is red or not, the other then denotes yellow or green. This reduces the number of addresses required and simplifies the use of common negative signals from Berko and Eckon which are wired via relays. It also means that if there if DCC power is cut, all signals go to red (they are fed from a separate 12v DC supply)


Control Software Screen Shot


The main control touch screen is mounted at the end of the layout on a control desk along with a rolling road that can be switched to DC, DCC or DCC Programming track. The computer software can also control the rotation of the turntable and can act as a loco throttle.


The operating desk showing the rolling road


A small track mimic panel is located near to Tedford depot and this shows the depot tracks and can be used to set routes when shunting in the depot. It is located on a small shelf along with a ZTC 505 controller which is used as a slave onto the Lenz system. The mimic panel is linked to the control PC via USB and acts as a keyboard interface, so routes are set in the same way as on the touchscreen. There is a USB LED driver in the panel and LEDs are lit up to show the button which has been pressed and the possible routes from that button.


The USB panel and ZTC controller


 You can see the slide show I presented to MERG about my layout's control system in April 2008 by clicking the PDF link to the left. Note that the layout has been developed considerably since I gave this presentation.