How do I stop my iMac from going into deep sleep?

I ask because I'm using remote tap on iPhone to remote into my iMac when I'm away. It sleeps it and wakes it just fine remotely... BUT when it's asleep too long, remote tap will fail to wake it, and the only thing that will wake it is if I hit a button on the keyboard or mouse. Is there a way to just keep it in normal sleep(?) or something? Thanks guys in advance

thank you sir