Is it possible to obtain a -12V supply (or close to it) from a max232?
Alex_rcpilot posted this image here where he obtained a +13V supply to use for programming PIC's.


Is it possible to get a -12v output? I'm trying to build a PID controller and there is an opamp that requires a +/-12 supply.

__________________
Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

The output from a MAX232 is usually about +/-10V or so, the circuit above looks to have an extra voltage-doubler to give it more.

The current availability from a MAX232 is only low, how much do you need?, and how critical is the voltage?. Is your only available supply rail 5V?, if you have a higher rail it would be easier to generate a -12V rail.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I only have a +12V supply and I need a +/-12V and a +5V.
I dont think there will be that much of a draw on the -12V supply. Its only used for the neg. supply rail of an op amp. So I have alittle play in the voltage levels (I think)

__________________
Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

Looking over the schematic some more, they do pull the -12V supply from the max232. Comes off of pin 6.

__________________
Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

Depends on what the op amp is driving. The output current comes from the - supply when the output is below ground.

__________________
I thought what I'd do was I'd pretend I was one of those deaf-mutes.