[sdiy] Re: LVM

[Tim Parkhurst]

> -----Original Message-----
> From: Roy J. Tellason [mailto:rtellason at blazenet.net]
> Sent: Tuesday, November 16, 2004 2:07 PM
> To: Synth-DIY
> Subject: Re: [sdiy] Re: LVM
> 
> On Tuesday 16 November 2004 12:26 pm, TIm Daugard wrote:
> 
> > 5.5V means I could use my huge stock pile of TTL chips!
> 
> You too,  eh?  I have a fair pile of that stuff too,  and it's 7400
series,
> not just the later 74LS00 series.  I'll figure out something to do with
them
> one of these days!  :-)
> 
> 
> 
Let's not forget that we don't necessarily have to redesign everything to
operate on 5 or 6V supplies. An LVM could use circuits with higher voltage
supplies BUT you need to make sure that any I/O is scaled for 0 to +5V and
electronically protected/limited. We don't really care about what goes on in
the circuit AS LONG AS we don't need to put a low-voltage programming
element (analog switch, digi-pot, etc) in the circuit. Many circuits in use
already have buffers on the inputs and outputs, so changing the scale and
offset of the I/O is not really a big deal. When using higher voltage supply
rails, zeners or some other relatively 'bullet proof' circuits should be
added to make absolutely sure that a short or other similar 'catastrophic'
condition could never put more than +5V (or much less than 0V) on the I/O. 

Tim (catastrophic shorts) Servo

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