Find router IP address?

When I was at school last semester my dorm didn't have wireless internet, but also didn't allow use of your own router. To get around this I set up my router as a wireless switch, not giving out IP addresses just distributing the wifi signal. In doing this I had to change the IP address. While moving back home I must have misplaced where I wrote down this IP address and have no idea how to find it. I have tried all the basic IP addresses but most bring me straight to the houses main router, byping my own.