Problem with discontinuity in NDSolve[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg4301] Problem with discontinuity in NDSolve[]*From*: a_kowald at chemie.fu-berlin.de (Axel Kowald)*Date*: Tue, 9 Jul 1996 00:46:47 -0400*Organization*: Kristallographic Institute FU Berlin*Sender*: owner-wri-mathgroup at wolfram.com

Hi everybody, I have a problem with NDSolve if my equation contains a discontinuity. If I try NDSolve[{y'[t] == 10 - y[t] * If[y[t]-15 <= 0, 0, 1], y[0] == 0}, y, {t,0,20}] I always get the error: Maximum number of steps reached. The solution should be a linear increase until y = 15 followed by an exponential decay until a steady state is reached by y = 10 Funny enough if I try NDSolve[{y'[t] == 10 - y[t] * If[t-15 <= 0, 0, 1], y[0] == 0}, y, {t,0,20}] causing the discontinuity to be at t = 15 instead of y = 15 NDSolve has no problems at all. (But of course this is not what I want.) ANY SOLUTIONS ??? ANY IDEAS ??? Many thanks Axel Kowald P.S. I'm using Mma 2.2 on a Mac with 7.5.3 and 24 MB RAM ==== [MESSAGE SEPARATOR] ====