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View Full Version : Regulator Problem UPDATE: More questions



Jake11611
03-25-2007, 09:05 PM
I got my 3.3 and 5 VDC regulators from Parallax earlier this week, but when I wire them up, they aren't regulating. I'm only getting about a 2 volt drop from 9 volts with the·5 volt reg. I've noticed that in the PE kit they are wired with a 1000uF capacitor. Is this capacitor necessary, or is it only for filtering? And if they aren't needed, is there something wrong with the regs?

Post Edited (Jake11611) : 4/2/2007 8:52:38 PM GMT

Steve Joblin
03-25-2007, 09:42 PM
Usually a minimum of two caps are necessary...

At a minimum, for the 5 volt regulator,·a .47uF·should be placed across the input pin and ground;·and a polarized 22uF·electrolytic·should be placed across the output pin and ground.

At a minimum for the·3 volt regulator,·a .1uF·should be placed across the input pin and ground;·and a 10uF should be placed across the output pin and ground.

To find out more, just google "LM2940CT-5.0" and/or "LM2937ET-3.3"

Jake11611
03-25-2007, 10:15 PM
Thanks, the regulators work fine now.

Jake11611
03-31-2007, 06:56 PM
What would be a good value for something on a robot, I noticed you said "At a minimum."