[sdiy] Digital Input Circuit
stewpye at optusnet.com.au
Sun Jun 16 03:51:22 CEST 2013
I'm designing a sequncer based around an AVR XMEGA microcontroller
powered by 3.3V. It has some trigger inputs that accept nominal 5V
trigger signals, though it should be able to handle any voltage between
-15V and +15V as it is part of a modular synth.
There are 8 inputs. The circuit I have drawn is a series input resistor
to the base of an NPN transistor. The emitter goes to ground and
collector goes to the input pin of the microcontroller (with internal
pullups turned on). There is a reverse diode across the B=E junction. Is
there a more elegant solution than this? An IC that will handle the
input voltage range required with just a series resistor?
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