Circuit DC to DC Converter ::
5VDC to +12V and -12V Isolated dual power supply

This is circuit Isolated dual power supply OR DC to DC Converter Circuit. Input Voltage 5V,Output Voltage +12V and -12V.

Detail:
diode should be fast recovery type, for less than 100mA use 1N4148. transformer, pri-20-20, sec-60-60, a SWG-AWG to suit the current you design for.

Any fast switching transistor would work, no regulation, use regulators like 78L12 if you want, circuit like multivibrator used for flashing LED lights.

Read More Source:
http://www.electronics-circuits.com/schematics/arc20050724.html
Thank you.