I am building a power supply and am wondering if there is a method to supply +15V,0V and -10V. I don't have any linear voltage regulators or zener diodes, also any SMPS device is out because of lack of breadboard space. The supply needs to be good for about an ampere. I do have a 24V transformer but it has no centre tap. I can use diodes to simulate the centre tap, but it is only half wave rectified.