I have written a small DOS program that only requires one or two circuit tracks or reed relays connected to your PC - and there's your low cost MRR speedometer.

An old PC (80386dx or better) will do - DOS, Windows 95, or Windows 98 will work.
You'll need a startup diskette if you use Windows Me, NT, 2000, or XP.
I didn't test the program with Windows NT, 2000, or XP yet - I strongly recommend booting DOS from diskette or CD.

I tested the program in a DOS window under Windows Me - and it had an awful impact on the accuracy.
So in order to get accurate timings and speed indications, use the program as recommended and run it under DOS, under Windows 95 or Windows 98 in DOS-Mode or after booting from a DOS diskette.

Further information can be found here: http://h0-freun.de/mrr/software/index_e.htm

Information is also included in the zip file http://h0-freun.de/software/patacho.zip (245 kB)
This zip file includes the English and the German version of PaTacho.

Feel free to ask questions here on the forum or via e-mail.
I know how the program works, but I don't know which problems you may encounter if you try to get it going.
Therefore: feel free to ask and help to improve the program and its documentation.

This is a DOS program because a) it's easier to access the parallel port from the program and b) accuracy is better because DOS is a single tasking operating system.
The hardware requirements are very low, so you can use your secondary or third-rate PC - and if you really have a 386, 486, or Pentium for that purpose, you probably have DOS, Windows 95, or Windows 98 to go with it.
I cannot say if a Windows version will follow; it will require a driver to gain access to the parallel port and other tasks running concurrently could reduce the accuracy significantly.

Great program , have already installed it here, though parallel port not wired yet as my layout is still under construction.

The timing of the MS-Windows operating system is indeed a major point. Ever tried to play a MIDI sound file ? I have installed in my OS/2 partition which has a DOS box with real time capability. Seems to work fine.

Hans Martin