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

[harrybissell]

If you have a supply like 15V available... using diodes to clamp the signals
is a good way to go (with a series resistor as someone already mentioned)

If not... I'd suggest a diode clamp to ground and a zener diode for the upper
voltage...

Zener diodes can have quite an effect on the signal as you near the zener 'knee'
voltage
though.

I like the zeners (generally) because an externally applied voltage cannot go
through the
input resistor, and clamp diode, and actually replace your normal power supply
(could
turn the unit ON when it is not powered...)

H^) harry

Bret Truchan wrote:

> Sorry if this is a duplicate message.  I had huge trouble posting with my
> mailblocks account.  Maybe this will work better...
>
> Hello!
>
> I have a newbie question for everyone! I'm creating a module that has
> a microcontroller on the back-end. It's supposed to be able to hook up to a
> Doepfer, Analog Solutions, Blacet, etc.
>
> The microcontroller has a bunch of I/O lines that are configurable as either
> inputs or outputs. I want to keep that flexibility. Some of the I/O lines
> COULD be configured as A/D converters, so I don't want to
> buffer these lines in any way that would force them into an +5/+0
> volt paradigm. The maximum voltage allowed on the inputs of
> the microcontroller is 14 volts.
>
> My question is, what type of circuit should I put on the I/O lines of the
> microcontroller to ensure that:
>
> * If a microcontroller I/O pin is configured for input, an incoming voltage
> signal doesn't peak over 14 volts
> * If the microcontroller I/O pin is configured for output, it still works.
> (The output will always be 5Vfrom the microcontroller.)
>
> Thanks a ton! If anyone has a schematic that could do this, that'd
> be great!!
>
> - Bret
>
> _________________________________________________________________
> Tired of spam? Get advanced junk mail protection with MSN 8.
> http://join.msn.com/?page=features/junkmail