TrainSpeed Hints & Tips

Using The TrainSpeed Model Railroad Speedometer

by Don Fiehmann

This series of tec notes is designed to help modelers. Much of the information comes from question asked by modelers and tips we have found. This note covers using the TrainSpeed1 and TrainSpeed4 model railroad speedometer. This speedometer works with either dc or DCC.

Need for Scale Speed
It used to be that you just ran a train at a speed that looked good to you. Now there are a number reasons to know the scale speed of a locomotive or train. With sound equipped locomotives running at a correct speed means the engine sounds are more realistic. If you use DCC, knowing the speed can help to set the top voltage (CV-5) in the decoder. When consisting a speedometer can be used to match the speed of the locomotives in the consist. It is also good to know just what is the speed of a locomotive.

How it Works
This TrainSpeed determines the scale speed by timing a locomotive’s speed over a measured distance. Small photo sensors in the track are used to trigger the unit. Room lighting is used as the source of light. The distances can be 1/50, 1/100, 1/200 or 1/400 of a scale mile. Jumpers in the circuit board set which measured distance is used. The microcode in the TrainSpeed also does some testing on power up that can detect problems with the sensors. The TrainSpeed comes in two models, either with one (TrainSpeed1)or four (TrainSpeed4) sets of sensors. With the four sensors unit the display will indicate which sensors were used for the speed readout. Speed readout can run from 1 to 999. This can be in either miles per hour or kilometers per hour by setting the correct measured distance between sensors.

Installation
The first thing is to read the instructions that come with the TrainSpeed. The information in this tec note is only a supplement to the TrainSpeed supplied instructions.

Power
The circuit board has an onboard circuit to convert input power from ac to dc. It also has a filter and a regulator to hold the circuit board voltage constant. This type of circuit allows the source of power to be either ac or dc. With the onboard regulator the power can be from 6 to 18 volts ac or dc. I tested the TrainSpeed4 and found that it would operate from 6 volts to 18 volts dc(the maximum) at less than 50 milliamps. An old power pack or one of the small plug-in-the-wall transformers can be used as a source of power. Tony’s has a 12 volts 0.5 amp power supply that works. Tony’s part number is XFRDTX.

Location
You need to consider the location of the section of track to be used to measure the speed and the location of the display. Since you need to have a measured distance, a section of straight track is the easiest to measure. Then you need to find a place to install the display that is near the sensors. This should also be a location that is close to the locomotive controls. If you are going to do speed matching the section of track to be used should have enough track before the sensors to reach full speed and enough room to stop after the sensors. The sensors use room lighting to activate them. The best source of light come from directly overhead. Light at an angle may not give as accurate a reading.

The unit comes with 10 foot cables with a connector on one end and the two sensors on the other end The cable can be extended up to 30 feet. This allows 2 additional 10 foot Extension Cables to be added to the 10 foot cable supplied with the TrainSpeed. The additional 10 extension cables are available from Tony’s.

The package includes a template to help you cut out a panel to mount the meter. For clear plastic the meter can be mounted with four 4--40 screws. If you are mounting the meter in an opaque panel a hole needs to be cut out for the display. I found it easiest to cut out the paper template and tape it to the panel. Then drill the four mounting holes. Next drill four small holes in the corners of the area to be cut out for the display. Remove the paper then scribe a line between the four hole in the corners of the display cutout. Then you can use the lines as a guide to cut out the hole for the display.

I used a jewelers saw for the display cutout. When you install the circuit board set the jumpers on the board for the ratio you will be using. (See the manual for jumper locations.)

Installing the Sensors
Each cable has two sensors that are installed in the roadbed below the track level and at the level of the ties. It is important to have the distance between the two sensors located as accurately as possible. As recommended in the manual use the longest distance practical for your scale. There is a chart in the manual to show the distances for 1/50, 1/100, 1/200 and 1/400 of a mile for most scales. The chart lists HO scale 87.But HO (3.5mm = 1 foot) is a little over 87 and is 87.086. This is only about 1% off and here is the numbers I have computed for sensor distances.

The difference between the two is less than 1%. If you are installing the four sensor model remember that all of the sensors must be installed at the same distance as the circuit can only be set for one timing ratio. (Like 1/50).

The photo sensor should be mounted so it the at the level of the ties or roadbed.

One way to accurately locate the photo sensors in the roadbed is to make a template. Start with a piece of thin strip wood that just fits between the rails and is a little longer then the distance between the sensors. Drill a very small hole near one end. Carefully measure the distance to the next sensor location and drill a second very small hole. The template can be placed in the location for the sensors and small pilot holes drilled thru the holes in the template. You may have to stick a small piece of wire in the small holes so you can find the holes when the template is removed. Then slide the template up and drill a larger hole and drill the final hole with a 5/32 or #20 drill. Now you can slide the sensor up from under the roadbed.

When plugging the cable into the circuit board be sure to line up the red strip on the cable with the pin number 1 on the circuit board. The photo in the manual on page 11 shows the cable going to the left. The cables supplied go to the right. Just remember to keep the red line and the 1 on the same side. I suggest that the cable not be run too close to the DCC power cables.

Operation
Once power is applied there is a startup diagnostic program in the microcode that checks for errors. This takes about 2 seconds. The manual points out that if you leave anything (locomotive, car, the manual and so on) on a sensor it will appear as an error to the startup diagnostics. Once ready to go the simple run a locomotive past the sensors and it should display the speed. You can also pass your finger over the sensors to test the unit. Too fast (Greater than 999) or too slow (less than 1) will produce an error. If you turn the room lights off the TrainSpeed will not work and show an error.

The TrainSpeed4 has four sets of sensors. I was concerned about what would happen if a train started over one set of and a second train started of another set of sensors. It turns out that the unit will continue with the first measurement and disregard any other inputs until the first one is finished. The reading stays in the display until the next reading is started.

A chart can be made and put next to the TrainSpeed display that shows the location on the layout of the senors. With the TrainSpeeed4 all four location can be on the chart. They can be listed like “1. = Olympia West 2. = Olympia East” and so on.

If you plan to do speed matching using the 28 CVs in the alternate speed table (CV 67-94) then you might look into doing it with a computer. The free program over the internet called DECODER PRO will work with most DCC system and with either an Apple Mac or a PC. The hole 28 speed steps can be adjusted using a mouse, then programmed into the decoder via a serial connection to the command station. Just do a search for decoderpro on the internet.