[sdiy] Modular synth input/output protection.

[harrybissell]

BE SURE that if you use zener, or shottky diode clamps that you have
series limiting resistance between them and the real world.

If not, youre just inviting the real world to ride your power supply
instead of
the module input... another recipe for disaster as well a blowing up the
zener etc.

If you cannot stand series resistance, consider using a Polyswitch fuse.
It is only a couple of ohms, but in a fault it gets hot and could go up
to 5K or so, limiting current to a safe value. I would not use these on
critical CV inputs for pitch (they will change slightly with
temperature) but
for audio ins or outs they'd be fine.

Have you considered assasination ??? KILL your friends if they patch
output to output :^P

H^) harry

Tim Parkhurst wrote:
> 
> On 1/22/06, Rykhaard D.A.M.I.A.N. <rykhaard at gmail.com> wrote:
> > This thread has given me an idea - that I'd like to know if anyone
> > else has already taken care of?  (I'm having a hard time, trying to
> > come up with a title for it.)
> >
> > My thought is - to collect the guidelines / parameters / cautions /
> > etc., for safety in designing and building a module.  As Dave had
> > asked - is there a way to protect a system's outputs from being hooked
> > up to other outputs?  Is this something that we still have to worry
> > about, these days, or are precautions built into the chips that we're
> > building things around?  (Or, transistors for that matter - as they're
> > quite often used for output buffers.)
> >
> snip...
> >
> > --
> > Take care,
> > Warmth and Peace,
> > Ryk
> >
> 
> Hey Ryk,
> 
> Here's an excerpt from Thomas Henry's Drum Cookbook. This section
> talks about synth standards and is itself from Bernie Hutchin's
> Electronotes:
> 
> *************************************************
> CONTROL INPUTS
> ·Voltage:           0 to +5V
> ·Impedance:     100K Ohm
> ·Overvoltage and reverse voltage protected
> 
> AUDIO INPUTS
> ·Voltage:           ±5V
> ·Impedance:     100K Ohm
> ·100k attenuators on the inputs
> ·DC coupled where possible
> 
> AUDIO OUTPUTS
> ·Voltage:           ±5V
> ·Impedance:     1K Ohm
> ·DC coupled where possible
> ·Short circuit protected
> ******************************************
> 
> >From what I can see, the protections listed above are taken care of by
> standard buffers on inputs and outputs, including 100k resistors on
> inputs going into an op amp buffer, and 1k resistors on outputs
> (usually coming from an op amp buffer). One place to watch out might
> be digital I/O. This is where I would probably use a resistor, zener,
> or schotky diodes to ground and +V (the digital supply).
> 
> Tim (enjoying a lazy Sunday morning) Servo
> --
> "Imagination is more important than knowledge." - Albert Einstein