emonGLCD change MEGA328 to 5v?

I am looking to use Pin9 out to control my heat pump....

Easy enough I thought and the software is ready to go, but I have just realized the mega is 3.3v powered so I can only get 3.3v out :-(

Can I just jumper the Vcc on the mega to the 5v input....or is that going to blow it up or break other things...

I need a 0-5v somehow. 






Robert Wall's picture

Re: emonGLCD change MEGA328 to 5v?

If you have a RFM12B radio module you might damage it. The maximum operating voltage is 3.8 V.

Why not use a small NPN transistor as a buffer? Drive the base through a current limiting resistor from the 3.3 V output pin, take the collector up to 5 V via the load you want to switch (a resistor if you just want a voltage at a lowish current) .

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