Thread: Very cool FM transmitter and easy wiring question

Originally Posted by shchua

I agree, but I think you meant the 7809 (1A 3 terminal linear regulator). Its recommended to have a 0.1 uF capacitor on the output for stability although you can get away without it most of the time.

Uh, it has been a while since I built any circuits like this, would you mind putting together a little wiring diagram for me? I'm not exactly sure what you are recommending. Thanks in advance!!!

Super easy. This is for the 7812, but the instructions are exactly the same.

Thanks Chairboy, I'll go to the store tomorrow and build this sucker. I think this is way better than buying something from Radio Shack. This should be the final component I need to finish up this thing, thanks for your help!

Pin3 is ground, not -12vdc nor -in.

So then, consolidating comments from this thread, this circuit should look like the attached picture? Can someone please confirm?

wait a second.... I need +9V DC out, not +12V DC out.... Anyone else have ideas????

the last two numbers of the chip give you the output voltage
therefore if you want 12v out use a 7812 or 9v out use a 7809.
also the circuit you drew is wrong as the capacitor should be between ground and the output, not in series with the output. if you are using polarised electrolytic capacitors make sure you connect the -pin of the cap to the ground.
the way youve got it set up at the moment will give you a pulsed output as the cap charges and discharges.
with the correct setup the cap is acting a a small storage area for power incase the screen demands more than the regulator chip can supply the cap is a kind of buffer.
i tend to use a cap at the input side as well for the same reason, slightly bigger but the values arent that important

sorry bout the poor diagram but this is how i would do it, maybe put an LED on the output side as a status indicator to tell you its working!!
now get soldering!