5v from 13v or 22v?

[stuee]

Hi,
I want to make a adaptor to able to plug into my car which is 13v ish and also interchange and plug into my solar panel if its sunny.
The mission for this is to charge my ipod and mobile which both have a usb charger cable when im away.,

I was looking at the L7805 but the i would like max 1A and also the input voltage is lower than 22v.

I have a l7808 here which i could use but not sure if that would be suitable and would need to take it down to my required voltage.
If someone could help me i would appreciate it (a schematic would be helpful too) also if this regulator is safe and wont fry my phone or ipod.

Thanks in advance..

 

[Jaguarjoe]

I use 7805's quite a bit and they have yet to fail. The max input to these is 37 volts, the minimum Vin is Vo + 2 volts, or 7 volts. If you intend to run at its max current of 1 amp, you will need to be mindful of junction temperature and power dissipation and heatsinks. With the best case of 7v in and 5v out at 1amp, you will dissipate (7 - 5) * 1 = 2 watts. At 50 degrees C per watt, the chip will be 100 degrees above ambient. This puts you very close to, or above the 125 degree max limit. You will need a relatively small heatsink. If you feed it 22 volts at 1 amp, you will need to deal with 17 watts and fan cooling. This is horribly inefficient. OTOH, a switching regulator is about 80 to 90% efficient. Most of the major IC houses have the chip you'll need along with a plug and play program that cranks out all of the values for the handful of other parts you'll need.

 

[MikeMl]

Just get an automotive cigar-lighter plug-in 5V cell phone charger. I have bought these at garage sales for $0.50. Most have this chip inside.

Your solar panel is 22V Open Circuit. I'll bet under any reasonable load it drops to less than 15V, so use the charger above unmodified.