Yigit, > How is the path geometry ? Rail line across the country. > What precision do you need ? (cm, m, 10m's..) May be a couple of 100 meters ... > Can you put the detector to 2km ? No, it needs to be near the lighting system. Wiring 2 KMs in rugged=20 terrain is not practical. > What kind of a train is this ? Regular passenger, express and goods train - electric as well as diesel. > If its going through a tunnel, the structure will act as a waveguide and > focus the sound waves as well. Too many parameters, I don't think a gener= ic > solution applies for this task at 2km's. I think measuring the impedance > across rails will give the most precise result if you do the impedance > matching carefully. You can develop EM based apps for this as well. We ne= ed > more initial conditions. I will think along these lines too. Once the official permission is=20 received, then I can go near the tracks :-). Cheers Ravi > > On Thu, Jul 18, 2013 at 1:31 PM, Ravi wrote: > >> Russell and Yigit, >> >> Ok, I am in India. The tracks run through tunnels. When the train is 2 >> KMs away from the tunnel, we need to switch on the light to 100% >> brightness and when the train passes away by 2 Kms, need to dim the >> light to 20%. >> >> Yigit, your idea of using the timetable is ok if the trains run on time. >> Well, here it is not so. Moreover if the time table is changed, then all >> the detectors needs to be reprogrammed in the field that is nearly not >> possible. >> >> Hope I have answered the questions. >> >> Cheers >> >> Ravi >> >> >>> On 18 July 2013 21:34, Ravi wrote: >>> >>>> Is there any method to detect an oncoming train about 2 KMs away? >>>> >>> >>> You must provide better information about your requirement if you do wi= sh >>> to avoid the 'death by 1000 cuts' answering process. >>> >>> Is it on an infinitely level bright white plain and travelling in a >>> straight line on a uneven joint per yard steel line with steel wheels, = in >>> bright sun light, shining a concentrated 10 million candlepower lamp, >>> blowing a dense plume of black smoke, sounding a 150 dB whistle and or >>> klaxon and with unimpeded line of sight to your observation point which >> is >>> dead ahead along the straight railway line? >>> >>> If not, please specifiy any areas where these conditions are not met an= d >>> detail what condition exists instead. eg In a dark tunnel with >>> depressurisation vents in pitch darkness, winding line, no light, rubbe= r >>> wheels, no sound, stealth radar coating ,,, . >>> >>> ? >>> >>> >>> R >>> >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .