need help in 24 to 5 volt DC/ DC converter circuit

Greetings all,

I need a 24 to 5 v (1 A) DC/DC converter circuit.Can i use 7805 ? please help me
thanks in advance.

Sure, you can, but why would you want to use a wasteful linear regulator when you can use an efficient DC-DC converter. They're sold as USB car voltage adapters or you can often find one that's been a cell phone charger at a thrift store for $1-$2. If you look at the labels, you'll see that most are rated for 12-24V input.

(24V in to the 7805)-(5V out)=19 across the regulator.

19V X 1A = 19 watts It is going to be HOT at 1A.