LM7805 driven switching regulator

Figure 1

INPUT 24V DC

J2

BD242

1

Q1

2

+ C 1 47 !F

J1 1 C2 470 !F

D1 1N5817

R1 47

1

L1 680 !H 1A +

2

OUTPUT 5V DC

R3

IN OUT IC1 LM7805/TO220 GND 2

3

R2

You can use a linear regulator in a switching circuit to configure an inexpensive dc/dc converter.