Monday, September 28, 2015

Catch Point and Indicator Update

I haven't had a post for a few weeks as Chris had a sudden gall bladder operation after two attacks in two days and last Monday I had a cataract operation on my eye that was infected when I had the shingles in March of 2013. The eye drops I had to take to clear up the infection in the eye ultimately gave me a cataract. So for some time I have been working with basically one eye shut to eliminate the blur. It was OK for driving etc. but not for reading, the computer and modelling. I now have to wait for about 6 weeks for the eye to settle down before I get my glasses sorted. So I still have dodgy vision for modelling, etc. but not as bad as before.

Anyway, my Shapeways 3D prints of the catch points (White Strong and Flexible) and the indicators (Frosted Ultra Detail) turned up last week and I have been assembling them to see if I have designed them well enough to have them actually work.

OK, well the catch point needs to be amended as the dog spikes are too fragile and I lost a number of them while inserting the rail. The rail was Peco Code 75 flat bottomed. I haven't tried MicroEngineering Code 70 as yet but it does have a similar base width so I would expect a similar result. If you get a catch point when I put them on my Shapeways Shop then don't paint the sleepers first, it just makes it harder to insert the rails and I lost a few more dog spikes doing this.

I have beefed up the dog spikes by 10% and raised them slightly to give better clearance for the angle of the rail bottom flange area but there is a limit before the spike heads will be hit by the wheel flanges. So far they are clear of 88 and 110 wheel flanges.

Printed Left and Right Catch Points as received
The catch point indicators were printed in Frosted Ultra Detail which gives nice detail but can have occasional slightly rough surface areas which is due to a support material used during printing. As usual, I used a rinse in acetone for 1 - 2 minutes to clean any oily material that is used to clean away the support material.

Catch Point Indicators - Brightness and Contrast adjusted to try to show the detail
As I mentioned above I inserted some rail into the sleepers to test the fit but also to test the gauge which was successful.

Check of rail gauge - Lower rail temporarily fitted
The three items attached to the sleepers are from left to right, a wedge that is fitted inside the lower rail to raise the wheels up and over the rail and two alternate sleeper extensions for mounting the indicator on. The sleepers plug into the ends of the main sleepers around the area of the point blade.

One indicator set clipped from the main sprue with most of the sprues cut away to assist with painting access
The rails were cut to size, inserted and glued in place with Super Glue (ACC). The point blade was filed to a taper and then cut to length. he main rail was filed away to accommodate the point blade where they meet.A MicroEngineering rail joiner was cut in half with a cutting disc in a motor tool. The joiner was held in a pair of pliers and it was opened up by inserting a scrap piece of rail into tit before it was carefully pushed onto the end of the rail in the catch point. Another piece of rail had one end filed to an angle to meet the rail before being inserted into the angled sleepers.

Part assembled catch point with an indicator
Here are several photos showing the catch point with indicator in a typical position in Bylong yard. Catch points were placed where a siding met the main line so that parked wagons would not foul the main if the rolled away. This catch point would need to be curved to fit in this location so I will build one from the new design when I get it back from printing. The catch points will be able to be curved by clipping away sections of the web between the sleepers on each side of the rails much as is done on flex commercial track. This is one advantage of the White Strong and Flexible material, the other is cost as the catch point would be exorbitantly expensive in the Frosted Ultra Detail material, 'horses for courses'.

Overall view of the location - A lit Clearance Post can be seen on the right
A closer view
A close up view of the indicator - The square section rotates to the other aspect (arrow)
Unfortunately I didn't design the operating component of the rotating indicator head well, it won't turn the head fully. It is amazing how it can be difficult to envisage the way something should work when designing in 3D but how obvious it is when you hold the item in your hand. I now know what I have to do to make the indicator aspects move through 90 degrees when the point blade moves, or I hope so.

Another set of prints will be ordered when I finish the design changes. I hope that this indicator can be lit from below the baseboard by an LED in a hole drilled from below but I will only find out once I try it. The light will have to go vertical (easy) then be bright enough to reflect out sideways  through the pivot, into the head section and out the small red lens and the arrow area. Fingers crossed on this one.

Finally, here is the NSWGR plan again.

NSWGR Standard Catch Point - 1936

Monday, September 7, 2015

Wired Bi-Colour 0605 Surface Mount Device Red and Warm White LED Issue

I recently ordered some wired Red and Warm White 0605 Bi-colour SMD LEDs on ebay for marker lights as I really don't like the red/cool white versions we seem to get on our locomotives.

When they arrived, I sat down to use them as marker lights on a Trainorama 44 Class and realised that I had a problem.

Size of a 0605 Bi-colour SMD LED
Just before I ordered them I was looking at wired RED and White 0605 SMD Bi-colour LEDs from the same supplier and had noted that they were wired with a Common Anode.

Well, you can probably guess by now what my issue was, yes, the Red/Warm White ones were Common Cathode!

Why is this a problem?

DCC decoders are designed for Common Anode, so if I had used the LEDs as they came I would have ended up with both Red and Warm White turned on at the same time.

So, I was left with little option but to rewire them. I had bought the wired ones to avoid just this scenario!

I bought a magnifying glass on a gooseneck from JayCar Electronics that has a small 5 X lens in the larger 2X lens, more expense but it will be useful I guess.

I took a piece of Bostik Blue Tak, made a small 1 cm ball of it and pushed it onto my workbench. Into this I pressed the 'lens' side of the 0605 LED exposing the wire connections on the rear.

I placed the magnifying glass so that I could see the LED through the 5 X lens.

I have a temperature controlled soldering iron with a very fine point which I used to unsolder the three wires.

Rear of a 0605 SMD Bi-colour LED - Correct Anode Common wiring
0605 SMD Bi-colour LED Circuit
As can be seen from the circuit above there are simply four contacts, one in each corner to solder to which made the rewire easier.

I took one of the two long wires and soldered it across the opposite two contacts than the ones that had previously been bridged. This now formed the Common Anode connection.

I shortened the long wire to the same length as the remaining wire to form the two Cathode wires and soldered them in place.

The first one took about 30 minutes of stuffing about but I can now do them inside of 5 minutes. So far I have done five.

I did try double sided tape first but I found that the LED moved around too much, the Blue Tak holds better as the 'lens' can be pushed into the Blue Tak for a better bond.

I don't know if all RED/Warm White 0605 Bi-colour SMD LEDs are Common Cathode, probably not, but I made this post to make the modeller aware of a potential issue.

Oh, yes, how many did I buy?


And no, I haven't installed them as yet, took the wind out of my sails a bit, not an uncommon thing of late.