Sunday, September 26, 2010

3.3v regulator for our Arduino I2C projects

We are using the onboard 3.3v output on our Arduino board to run the SHT21 temp/humidity sensor. It's limited to 50 ma, so we are building a 100ma circuit, using the LE33CZ-TR voltage regulator, and two capacitors. We are using a 12v nominal input, but this circuit will handle up to 18v input (for when the house batteries are charging at 14.4 or so, and the occasional 15v equalize).

497-4258-1-ND (LE33CZ-TR 3.3v Regulator) $0.88

BC1148CT-ND (.1 mf 25v ceramic cap) $0.44

445-2866-ND (2.2 mf 25v ceramic cap) $0.26

I will be building a 5v regulator soon as well with the same input requirements, using the LE50CZ-TR 5v regulator, but Digikey did not stock this part at the moment. The inhibit circuit shown does not exist in the 3 leg TO-92 package, only in the surface mount 8 pin SO-8.

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