Another Servo problem solved

Not much progress on Freshwater for a few weeks because another problem arose with the servos used for points and uncoupling magnets. As I was adding more and more servos to the layout, I started getting problems switching on the power. On switch-on, the servos would move rapidly, hitting the physical limits of the mechanisms they are attached to, and carry on trying to drive past them. The current drawn by all the servos was collapsing the voltage from 16V AC down to about 3 volts. All this was happening before the PIC microcontrollers had time to initialise and bring the servos under control, and the voltage then dropped below the PIC operating voltage, so they stopped doing anything.

Consulting the Merg forums, I was advised to add some pull-up resistors to the servo signal lines. Apparently this stops the switch-on spike which sends the servos trying to reach their end limits long enough for the PIC microcontrollers to initialise and start sending sensible control signals to the servos. The pull-up resistors are 10k ohm, large enough not to affect normal operation. A change to the PIC software to speed up the initialisation process was also suggested, but has not been necessary. Having added the resistors, everything seems to be operating correctly again.

So, now I just have to build one more servo operated uncoupling magnet set and the electrics under the layout are done. Then I can start ballasting the track. Other jobs in the queue are:

- building a lighting gantry
- adding backscenes, and a transportation case
- replacing the temporary control switch box with a proper control panel (using CBUS kits to allow route setting)
- building a larger fiddle yard now the GJ challenge constraints are out of the way
- creating buildings and scenery

Ian Morgan
Hampshire

Magnetic uncouplers for Freshwater

Following the Expo, I can now get on with adding the uncoupling magnets. I had always intended using permanent magnets, following their successful use on Brunswick. I bought some small magnets from Merg, but they were nowhere near powerful enough to operate the DG couplers. Now I have purchased 50 'rare earth' magnets via Ebay. These are really powerful for their size (about 5mm diameter and 3mm long) and come with all sorts of warnings. 'Rare earth' magnets have a high iron content and would corrode very quickly if not protected by a special coating. Often this is nickel plating. It is therefore not practical to cut them, and you have to protect the plating from damage.

I planned to use some more servos, as used to operate the points, to move the magnets into position under the track, or away from the tracks when uncoupling was not required. The layout has several parallel tracks at various positions where I wanted uncoupling to take place, so I planned to have a number of magnets alligned to the parallel tracks, all operated by a single servo. I cut a length of paxolin sheet, and drilled it to take the magnets, which are glued in with epoxy. Working with the magnets is interesting, as they fly around the workbench attaching themselves to tools each time you get anywhere near them. Trying to get three magnets into their holes in the paxolin to glue them without them flying to each other was also quite fun.

I made a paxolin 'arm' which bolts to one of the servo attachments, and the bar with the magnets attaches to the arm, using bolts and a paxolin block with threaded holes in it. Because of al the tracks above where the servo needed to be, I cut a sheet of hardboard to attach the servo to, which bolted under the layout away from the tracks. The photos show how it works, I hope. One shows the magnets moved well away from the tracks, and the other two show the magnets in position hard against the underside of the layout surface, below the three parallel tracks there. You can also see the Merg Servo4 board that the servo plugs into. Now I just need to build two more.

Freshwater Behaved Itself

We had a great weekend at the Expo - lots to see and spend money on. Dave Stratton lent a hand carrying and operating, allowing me to roam a bit with the video camera.

I had the layout operating with nearly a week to go, and I chose to give the track a last minute paint job. I did not find time to add rust to the rails, just a spray of undercoat, and some paint slapped on the concrete and timber sleepers. It took an hour to scrape the rail tops and free up the point blades, but it was ready to go when the doors opened.

The layout performed a treat all the weekend, once the rails and wheels were cleaned and the back-to-back of several wagon wheels reset using the gauge. I am really glad I concentrated on getting the track right rather than pressing on with the scenery, as it is a pain to sort out with delicate buildings in the way. Now I can start laying ballast. I was definitely not going to do that before the Expo.

Uncoupling was achieved using a hand held rare-earth magnet waved about underneath the baseboards. 50 small rare earth magnets have now arrived in the post (ebay) which I will now produce a mechenism for. To shunt the kick-back siding, couplings had to be added to the other end of locomotives which previously only needed one coupling for shunting on Coley Park. It does add some interest to what is a much smaller goods yard though.

The servos and merg Servo4 control boards worked perfectly and did not require any attention all weekend - very promising.

The ability to switch from analogue DC to DCC and back again was of interest to some people, and when a wheelchair-bound friend turned up, we managed to lower the complete layout for him, using the adjustable trestles, returning it to our height later. This was not as easy as hoped, and will probably not be repeated, but it does show that we can chose what height to set up at before each exhibition.

I just have this out-of-focus pic of Dave shunting:



Ian Morgan

Fresh(er)water wiring completed

A weekend exhibiting Coley Park at Yeovilton followed by a weekend in Slovenia on a business trip slowed progress, but last week saw the completion of the wiring for the point operating servos to a 'temporary' switch box which will be replaced by Merg CBUS control one day. Unfortunately, two of the Merg Servo4 controller circuits I built last summer failed to respond to the setting up box. I only had 5 of the 7 points working.

However, I checked the Merg forums and it seems that there was a fault with programming the PIC microcontrollers for the kits last year (since fixed). An email to the Merg kitmaster saw a speedy response, and two new microcontrollers turned up in the post this morning. They are now fitted and working, and the two faulty ones will be returned for re-programming. Many thanks to Martin (Merg kitmaster).

The fiddle yard has one length of track laid and wired up, but that is all for now.

I have also added some more bits of wood to the underside of the baseboards to protect the wiring, servos and circuit boards during transit, and have purchased wood and bits to build the lighting gantry, but it was just too hot to do much today.

So, at the AGM, there will be plain, unballasted track and no scenery, but quite a lot going on underneath the baseboards, and hopefully trains running (analogue DC and/or DCC).

Ian Morgan.

Another milestone - trains running

This week saw the completion of the track wiring, and the successful test running of trains all over the layout. There was just one missing link wire found. Wiring up the point operating servos is still to be done. From the photos you can see one Merg Servo4 board mounted under the baseboard. Two more of these will be fitted to control the remainder of the points, and the, as yet, non-existant uncoupler magnet devices.



One inovation I have added is to allow instant switchover from analogue DC operation to DCC operation. The rails are divided up into sections, as normal. Individual lengths of rail in a section are linked up by the copper tape runs beneath the layout. The point 'frog' sections are kept as short as posible, and are fed from microswitches operated by the point mechanisms, switching between the two adjacent stock rails. Each rail 'section' is kept separate on the layout, and are fed by wires from a single multipole connector (an old Centronics parallel printer socket with 36 pins.



I then added wire links inside a plug to connect the sections together. For analogue DC, siding sections are linked to 'frog' sections so that they are isolated by the points. Another plug, for DCC operation, would link together all the left-hand rails, and all the right-hand rails, and leave the 'frog' sections unconnected.

SR Buffer Stops

At last, some spare time for modelling this weekend, so I worked on making up the lovely etched buffer stop kits I got from the 2mm Scale Association. I had started one a few weeks ago, but a good day's work today sees completion of all five required by the layout.



These kits make a form of buffer stop I was not familiar with, but I have found a very similar looking one at the eastern end of Ascot station, unfortunately not in easy reach of a camera though.

The beautiful, and cleverly designed etch is in nickel-silver. I really like using this material. The etch folds up, eventually giving 6 layers which all line up accurately for 'sweating' together with the soldering iron. The triangular gussets that attach the front 'leg' to the rail are a bit fiddley to line up and attach though.



I used real wood (recycling a coffee stirrer) for the beams rather than using the 5-layer etched beams provided. It feels more appropriate, and is electrically insulating, but proved tricky to attach using superglue. The tie-bar passing through small drilled holes in the uprights was a bristle from a large brush - also electrically insulating.



It seems my painting skills have lapsed over the long period since I last did any, and my hands seem to be not as steady as they used to be, but applying red and white paint on the ends of cocktail sticks, I managed to straighten up the lines fairly well.

Fresherwater tracklaying completed

A milestone (or is that a millstone?) has been reached. All the track is now laid, except for the buffer stops which will be the eagerly awaited etched SR kits. I have made a start on installing the dropper wires, and one point mechanism and servo is in place, so I have some way to go before proper testing of the track can start.

As can be seen from the non-painted track, there was a lot of curved track required (half track created in the jig, then the second rail being added using triangular gauges once glued in place). I had some shorting sleepers on these stretches which had to be sorted out in-situ and took some time to find and fix. This is one advantage Easitrac has over copper-clad.

I would like to get the wiring done by the end of March, but we have the Basingstoke exhibition using up one weekend (Highbury colliery will be there).