Dear ambrose,
OK, I will give you a simple schematic, which I tested with low current IC's like UM3482,UM3484,UM66,UM3561,UM3562,NE555,LM741 & LM556.
It ulilises R1 as a series droper.D1 rectifies the voltage obtained through R2,while D2 stabilises the output to the specified voltage. C1 filters the output.This is capable of supplying 25mA current and almost any voltage ranging from 3-24V by selecting suitable components for R2,D2 & C1, even if the input Ac voltage varies from say,195-270V.The output is sufficiently regulated.
The current supplying capability can be increased to about 40-50mA by using a 5.6K,20W resistor as R2,but this would require the use of at least a 1W zener.You may select the output from the following table.
For 3V output, R2=15K,D2=3V & C1=220uf
For 6V output, R2=12K,D2=6.2V & C1=220uf
For 9V output, R2=10K,D2=9V & C1=220uf
For 12V output,R2=10K,D2=12V & C1=470uf
For 15V output,R2=10K,D2=15V & C1=470uf
For 18V output,R2=10K,D2=18V & C1=1000uf
For 24V output, R2=8.2K,D2=24V & C1=1000uf