[sdiy] "Expression Pedal" output protection?

[Harry Bissell]

Yes, that's true. In this case there were hundreds of units on line, already
working. So the 'fix' had to be a retrofit. All you need to do is make sure that
600VAC can't blast a 24V input.

Linear Tech once had an appnote for a "Fault Tolerant Network Design"  in effect one that could take 120VAC from a wiring mistake witout blowing everything up.

We had some industrial networks blown up because we used a four pin connector for power (120V, 24V, common, gnd)
and the same four pin connector for the network. Oopsie !!!  The fix was to switch to a six pin power connector
that cannot be connected to the four pin network. Problem solved.

That advise was given on the list just a few days ago :^)

The best solution is to think of how much protection you can add vs. how much trouble the protection is.
For many people its a series 100ohm - 1K ohm resistor on an output :^)

H^) harry

----- Original Message -----
From: Neil Johnson <neil.johnson97 at ntlworld.com>
To: Harry Bissell <harrybissell at wowway.com>
Cc: Tom Wiltshire <tom at electricdruid.net>, sdiy DIY <synth-diy at dropmix.xs4all.nl>
Sent: Mon, 26 Sep 2011 15:24:29 -0400 (EDT)
Subject: Re: [sdiy] "Expression Pedal" output protection?

Hi,

Harry Bissell wrote:
> Yes, if you wanted to, you could make it fail-safe. It would not,
> however, be cost competitive with just replacing the cable correctly
> the first time. How to do it is left as an exercise for the reader
> :^)

The "cost competitive" bit depends on many factors.  For example, what 
was the cost of downtime while a new unit was sourced and commissioned? 
  What was the possibility of failure taking out other control units 
connected to the unit?  And so on.

As with many things, "cost" depends on who you ask!

Cheers,
Neil
-- 
www.njohnson.co.uk

-- 
Harry Bissell & Nora Abdullah 4eva