[sdiy] CV --> microcontroller, how to limit input voltage?

[Paul Maddox]

Bret,

> The maximum voltage allowed on the inputs of
> the microcontroller is 14 volts.

yeah but I bet thats not continous, I bet thats only instantaneous!

> * If a microcontroller I/O pin is configured for input, an incoming
voltage
> signal doesn't peak over 14 volts

several methods..
1)I would use a small resistor in series with the input pin (say 500Ohm) and
a zener diode (ideally the same voltage as your micro runs off, for example
5v1 for a 5V micro) this will stop things going above 5.1v, and
below -0.7v..
2) diodes attached to both supplies (like crow says)
3) If you know what level the voltages are, use a dividing network, for
example, if they are always going to be 0v -> +15v, use a 2K and 1K resistor
to give you a swing from 0v -> 5V...

> * If the microcontroller I/O pin is configured for output, it still works.
> (The output will always be 5Vfrom the microcontroller.)

use a transistor to buffer the output, this way you can get the output to go
between 0v and +15v if you want, or by using scaling resistors, again you
can choose what you want 0v -> 7.5v for example.

Paul
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