Hi, I am building my own digital photo frame. I am using a Haier 7" LCD TV for the screen, which requires a 12V input, and the SanDisk Digital Photo Viewer (SDV2-A-A30), which requires only 5V of power. I understand I could possibly use a 5V regulator, but I don't know where to insert that into the circuit, or if I would possibly need a diode or heatsink or anything for it.

Essentially, I'm connecting the digital photo viewer to the 7" LCD screen, but I only want to use one AC power adapter for both parts. All suggestions are welcome. Thanks!

 

You don't say how much power the SanDisk Digital Photo Viewer requires. You did mention 5v. If the amount of power is pretty low, you could use a 7805 regulator with an 0.33uF cap from IN to GND and an 0.1uF cap from OUT to GND.

Feed +12v to the IN terminal.
Connect the GND terminal to your supply return, and the SanDisk Photo Viewer ground.
Connect the OUT terminal to your SanDisk Photo Viewer +5v in.

If the current draw is of any significance, you will need a heat sink on the 7805.