Quick Tip: Big jumps

Some DCC CVs have a valid range of 0-255. To determine the proper setting, increase the value by 20 or 32 instead of 1 or 2. When you get close, then change the value by smaller steps.

Hexadecimal Programming

While programs such as JMRI have abstracted many programming details away, there
are several places where it may be useful to look at the CVs directly and in
hex. Trying to use "normal numbers" or base-10 to program CVs may make things
harder than they have to be.

Some CVs such as CV29 can be thought of as a series of 8 on/off switches.
Programming these CVs in hex can be much easier than using decimal. If you want
to turn off bit 3, using decimal you have to subtract 8 or using hex all you
have to do is set the bit to zero and look up the new value.

8-bit hexadecimal can be thought of as two groups for 4 bits. The low nibble
contains the first 4 bits (0-3) and the high nibble contains the next 4 bits
(4-7). The two groups are side-by-side to complete the byte. 0100 0110 is
0x46.

Memorize this table:

Nibble Hex
0000 0
0001 1
0010 2
0011 3
0100 4
0101 5
0110 6
0111 7
1000 8
1001 9
1010 A
1011 B
1100 C
1101 D
1110 E
1111 F

The low bit (0 & 4) is the rightmost bit.

To change a bit, leave the others alone and change the appropriate value. Look
up the new result in the table.

To use Hexadecimal mode with the DT40x-series throttle during programming, set
the left-hand value to something other than an address and press the right knob
once. (It does not appear address programming can be done in hex.)

Quick Tip: Remove masking tape quickly

In building my scenery, I often use plaster of paris for the base. The track is already laid, so it has to be masked before applying the plaster. There's a lot of working time between applying the plaster and the time to remove the tape, but the time is not infinite. It may remove just fine the next day, but the cured plaster will prevent removal soon afterwards.

Interior Photos

In the last couple of posts, lighting an office and adding an interior was discussed. Here are some photographs to show the results.

Dremel attachment

I've used a variety of Dremel motor-tool attachments, and have found one that works really well for model railroad use. It's the 423E cloth polishing wheel. The wheel consists of several layers of cloth, which when combined with a proper polishing compound works well to get the crud off of wheels and track.

Before getting out the wire brush attachment, give this a try.

The Interior

As mentioned in my last real post, adding an interior to the lighted building was now a necessity. The building is in a very visible location on the layout, and looking into the office will be easy.

The hardest part about adding an interior is simply deciding what to put in it. Desk, file cabinets, pop machine, boxes, pallets, what kind of junk accumulates in an office of a warehouse? Rather than fully detailing the office, I added only four items: A table, a man with a briefcase, a woman, and white bear.

The floor was painted a grey color, with the same color used on the lower part of the wall as a chair rail. This may not be noticed, but it might help complete the scene.

Plastic glazing over the windows improves the look of the building while tending to obscure some of the details inside. This means that the items inside do not need to be A++ grade models, but only need to be C-grade models. The table, for example, leans a little and was quickly assembled, but I doubt anyone is going to notice.

Looking in the big window, you see the table, the lady looking at the direction of the bear in the corner, and the bear. The man was going to be visible through the glass on the door, but a small mishap with glue obscures him.

At night, with the room lights out a nice glow comes from the office windows. When you get close, the interior is visible and the effect is excellent.

Update to Version 1.0!

Version 1.0
-----------
1. Display of main posts are now CSS instead of tables.
2. Post a new message page UI redesigned.
3. Goals update page displays error messages correctly now.
4. Index page uses CSS completely
5. Added code to support version 0.8's lack of timezone identifier. PHP may still complain, but at least the code will run.
6. Updated SQL for version 1.0 updates; refactored update file to allow future updates to be easier.
7. The reset button on the post comment page has been removed.
8. Refactored category edit/delete page
9. Added comments_allowed field to install code
10. Refactored add admin page.
11. Updated, cleaned a bit, and refactored comment control pages.
12. Eliminated processing pages for forms.
13. Refactored unregistration page.
14. Removed API functions display_error_message and display_status_message
15. New API function: MessageBox(2-3)
16. The entire system has had a face lift. All pages now use CSS to enhance appearance. (The real reason to use CSS, eh?)
17. Broke up functions page (users shouldn't notice a thing).
18. Consolidated new post and edit post pages.
19. New Feature! HTML on individual main posts can be turned on and off.
20. Comments can be disabled on a per-post basis.
21. Commenting cut off date can be disabled on a per-post basis.
22. Colors and Options are now separate in the database.
23. The only reset buttons that remain are those on the options and color change pages.

Lighting an office

Adding light to a building demands a higher level of attention to the building. On the layout, the building will attract attention, especially if onlookers can see into the building. For this added detail, however, a certain price must be paid.

Light leaks through anywhere it can. The plastics used in many model kits tends to be translucent, especially if a light source is located near to the material. Gaps between corners and materials need to be sealed with a sufficiently light-proof coating to prevent light from getting out.

One method used to address the translucence issue was simply to paint the building, both inside and out. Several coats of paint will eventually build up and prevent light from passing through. A method I have not tried would be to line the building with an adhesive metal tape. If only doing one room, this might be an ideal solution.

Sealing gaps tended to be relatively easy because they were small. The building was intended to be lit from the beginning, so careful attention was paid to gaps to ensure they were as small as possible. In the case of this building, one gap was sealed by gluing a piece of styrene between the adjacent wall panels, while others were closed by using a gap-filling CA.

For the most recent building, only a small office in the much larger warehouse was being lit. The whole building was prepared to be lit, in case the office light leaked. It did. The office was lit with two small white LEDs through the ceiling.

When an LED lights, the entire thing glows and can put off considerable light. It may be necessary to mask the back and sides of the LED to reduce the amount of light escaping. One corner of the building leaked, but masking the LED reduced the excess light enough that no further work was necessary.

Now that the office has lights, it's quite easy to see that there's nothing in there. An interior seems to be a necessary next step....

...and that's why you need the marker

As my train was departing the yard, I was looking for some kind of marker (flag, push pin, etc) to put on the end of the train. I grabbed a push pin off the bulletin board, and was immediately asked about it by one of the club's young members. Explaining that the marker indicated the end of train, rather than using a caboose, the push pin fell off and I could tell it wasn't going to stay on without a lot of help.

Since this is a model railroad, I just decided to go on without it. After finishing my switching, I returned to the yard with the empties I had pulled out and as the train became visible there was a new car on the front.

That was the car I tried to put the marker on. Guess I needed it anyway...

Block Detectors

I've been using transformer style block detectors to signal my railroad. The design I'm using says it can detect current as low as 1 mA, but in practice I've found 4-6 mA to be required. Now, I don't doubt the documentation, it's just my results differ. The transformer style of block detector is sensitive to things such as wire routing and number of turns, so it's easy to see why the results differ.

Now Team Digital has a transformer style block detector that looks like it uses the same basic design as the one I'm using. (I have not actually examined it.) The manual states a typical detection current of approximately 3 mA at 5V, which is similar to what I measured with the above circuit.

Connecting the block detectors is a matter of taking 22 ga magnet wire and wrapping it around the transformer 4 1/2 times inline with the power lead. Originally, I had used solid 18 gauge wire and wrapped it around 1 1/2 times. Detection current was somewhere around 10-20 mA, which isn't bad until you realize that equipping every car on a layout to be detected would soon result in even a small layout running out of power.

The magnet wire reduced the current required to approximately 5 mA, which means that 100 cars would draw 1/2 A. The trick is to get the block detector as sensitive as possible (to reduce current draw), while keeping it from detecting other things, such as a hand across the rails.

Trip current has been measured by clipping a 25K variable resistor to the rails and adjusting it to the point where the signal changes from green to red. At that point, the resistance is measured and Ohm's Law is use to calculate the trip current. After adding the magnet wire, my values usually fell in the 2.20 kOhm range. The track closest to the block detector measured 3.20 kOhm, which is only 3 mA of current. Perhaps better results are received when the block detector is close to the track rather than located on a control panel away from the track.

These values are important for choosing resistors for rolling stock. If a car has more resistance than the value, it will fail to be detected. If it has too much less resistance than that value, it will draw power needlessly. Some modelers use a 10K resistor for their cars, and report success. Two resistor equipped axles per car results in a draw of approximately 2 mA. My testing indicates that 2 such cars would need to be in the block to be detected. Equpping all 4 axles with a 10K resistor would result in a car that draws approximately 5 mA and should be detected.

Adjusting the resistor size to fit the block detector can reduce the amount of work necessary to equip cars for detection. As in the above example, equipping cars with 10K resistors results in a 2.5K resistance per car, something that could be done with 5K resistors on only two axles.

Some question remains in my mind whether only the caboose or last car needs to be detected. If the middle of the train is not detected, the signal behind the caboose would still be correct (while the one ahead of it would not.) However, in areas where the signal is protecting a switch, detection in the middle of the train may be essential.

Results differ based on the installation and what size resistor a railcar has been equipped with. Installing the block detectors first and then adjusting the wheelsets to match up with the detector's needs seems to be the best way to go.