24VAC Transformer from Air Handler, 7805

[Melanie]

Take your AC voltage, when full-wave rectifying it you'll have VACx1.414 as an off-load DC across your primary smoothing Capacitor. In your case that could be 27.6 x 1.414 = 39v. An inductor isn't going to do much for you... you need to loose 10-15 volts somewhere or use a different AC source. Your Transformer might be 24v... but it might also have additional tappings (ie 12-0-12) or similar.

[mister_e]

Some readings

Linear and Switching Voltage Regulator Fundamentals
http://www.national.com/appinfo/power/files/f4.pdf

TL783
Vout(Min)(V) 1.25
Vout(Max)(V) 125
Iout(Max)(A) 0.7
Vdo(Max)(V) 20
Vin(Min)(V) 21.5
Vin(Max)(V) 150
Pin/Package 3DDPAK/TO-263,3TO-220
http://focus.ti.com/docs/prod/folders/print/tl783.html

Example Transistor Circuits
http://www.satcure-focus.com/tutor/page5.htm

Serie voltage regulator
http://www.tpub.com/neets/book7/27k.htm