5v regulator with solar cell


I got a 10W Solar panel which delivers around 18V. I tried a 5v regulator to get 5v for powering several things. But the 5v regulator makes strange noises like wheezing at high frequency.

It sounds like some 220 DC Adapters... What can I do?

Thx Andy

Sounds like you're over voltaging the regulator. Is it hot to the touch? If it's anything like the Duemilanove's regulator, then it's absolute maximum rating is 18 Volts, and that's typically with a heat sink.

how much curent do you need and what's the rated output of the cell(maybe 200 ma)?

Obviously the 18v isn't ideal for powering a 5v circuit but if you have enough current for your needs you can just drop some of the voltage with a resistor.

For the record, I've never heard a voltage regulator whimper. I have read that they can oscillate if they don't have capacitors but i wouldn't have thought you could hear the poor things.

No it isnt' hot and it's an LM7805.

Current will always stay under 800mA normal at around 300mA.

So what do you recommend?

300-800 ma is a lot. Can your cell deliver that?

If so, you'll be dropping something over watts in the regulator. I would think it would get pretty hot.

Assuming the cell can deliver the amperage, do you have capacitors on the regulator input and output?

ok the maximum is ~700mA, but now during winter I get just around 100-150mA. I got capacitors just at the output, ok I will try this...