How does the Tech reader work on MTH protosound 2.0

The reader is a reflective sensor, it has an IR emitter and an IR receiver (photo transistor) in a single package.  When you look closely at the face, you see two rectangular lenses, one is the IR emitter and the other is the IR receiver.  The white stripes reflect back to the IR receiver and cause current to flow between the emitter and collector.  The black stripes don't reflect much and very little current flows.

The reason so much is said about the spacing to the flywheel tape can be gleaned from the following response chart, at around .75mm from the tape is the maximum sensitivity.

Thanks you are the best, not only do you know how but you know how to explain.

I greatly appreciate you sharing your knowledge.

I'm accomplished at looking things up.   This just happens to be something that's in my wheelhouse since I actually designed a product using this very technology, the Chuff-Generator.  I use the same kind of sensor on that as the one used for PS/2 tach reader boards.

AAMOF, I even made a replacement PS/2 tach reader board using a different but similar sensor as is used with the factory PS/2 tach reader.  Replacement MTH DCS Tach Sensor Board

@gunrunnerjohn posted:

I'm accomplished at looking things up.   This just happens to be something that's in my wheelhouse since I actually designed a product using this very technology, the Chuff-Generator.  I use the same kind of sensor on that as the one used for PS/2 tach reader boards.

AAMOF, I even made a replacement PS/2 tach reader board using a different but similar sensor as is used with the factory PS/2 tach reader.  Replacement MTH DCS Tach Sensor Board

John would really be cool if you could design a tach reader using stripes on the flywheel that would work with LionChief + boards.                   j

@JohnActon posted:

John would really be cool if you could design a tach reader using stripes on the flywheel that would work with LionChief + boards.                   j

Actually, I'm looking at doing a replacement tach reader for Legacy, and the LC+ and LC+ 2.0 boards use the same technology.  The bonus of making a reader that operates from the tach strip would be with a custom strip you could adjust the speed steps to match the gear ratio of non-Lionel engines so that lash-ups with other engines would work properly.

My replacement tach reader will be the same hardware as the Chuff-Generator, just new programming.

@gunrunnerjohn do you happen to know the insulation colors for the A, K, C, and E connections for PS2?

And while I'm at it, how about for Sunset 3rd Rail's tach sensor?

Or, possibly, a procedure to identify them?

@Ken Wing posted:

@gunrunnerjohn do you happen to know the insulation colors for the A, K, C, and E connections for PS2.

@Ken Wing posted:

And while I'm at it, how about for Sunset 3rd Rail's tach sensor?

The only 3rd Rail sensor I know of is the older TAS cruise that was used until around 2007-2008.  They didn't seem to have a consistent color code, but RED =+5VDC, BLUE=TACH OUTPUT, BLACH=GROUND, see graphic below.

@gunrunnerjohn may I just say how awesome you are!!!

So is it possible to use reed and magnet instead of tech reader by only using the plus power lead and tach plus lead ?

@Michael Roth posted:

So is it possible to use reed and magnet instead of tech reader by only using the plus power lead and tach plus lead ?

No, there is no way it would ever be fast enough.

The question is about PS2- in order for speed control to work, which also is related in pulse count to chuff- you need a fine pitch encoder- typically 24 stripes on the flywheel. There is no way a reed switch and magnet can ever fire fast enough, even if you reduced the pulse count- you basically kill off the speed control performance.

A key factor can be seen using ADPCM to analyze the MTH sound file structure.

The typical MTH flywheel is 24 stripes per 1 rotation of the motor. The sound file also uses the gear ratio of the gearbox and wheel size to understand pulse count for distance, which is how MTH engines are calibrated in scale MPH. last, the chuff rate is known, also by the gear box ratio and one rotation of the wheel = how many pulse counts at the motor rotation- divided by the number of chuff per  rev is the count per chuff. Again, there is no way a reed switch and magnet can ever achieve these rates even at slow speed.

@Michael Roth posted:

So is it possible to use reed and magnet instead of tech reader by only using the plus power lead and tach plus lead ?

Also, even in my answer above I missed a detail- the pulse is grounding(negative) not positive.

In other words, not only would the reed switch not work, but you have to pull down (ground) the pulse lead, not pull it up to the positive lead. Again, tach pulse lead has a pullup resistor (hence it is normally positive compared to blue) and source at the PS2 board, the optical sensor is then grounding that lead to the blue minus lead with each pulse. Also worth saying- that minus lead is also not frame ground- that is digital PS2 board level ground.

Rule#1 in most any modern engine, including MTH PS2 is none of these wires can ever be at frame or AC potential.