Newb Q: How can I clamp voltage at 9v?

BigMike

Hello,

What I have is a variable 11-15 volt power source and I would like this source to run my BASIC Stamp board.

A while ago I thought I heard about a voltage clamping device that would regulate a higher voltage source to always output to 9 volts, but now I can't seem to find anything..

Could someone help me please? I suppose I could always use resistors to drop the voltage, but I thought there was a much cleaner and more accurate way to do this. I know the Stamp will run through a range of voltage, probably like 7-10 volts, so yes, I can use resistors, but again, that will waste current and if there is a better way to do this please let me know!

Thank you in advance,
BigMike

Mike Green

You can use a "3 terminal voltage regulator". For running a Stamp board that has its own voltage regulator, you want an 8V supply ideally and the "LM7808" will take the sort of voltage you have and produce 8V. There's also an LM7809 if you want 9V. The datasheet is here www.fairchildsemi.com/ds/LM/LM7808.pdf and includes sample circuits. Be sure to use the recommended filter capacitors.

Another option is to use a Zener diode. The Wikipedia has a good discussion of this: en.wikipedia.org/wiki/Zener_diode.