[sdiy] Gate outputs.. 0v or ground?

[Mike Beauchamp]

Thanks for the reply Paul,

> The problem isn't at the 0.0 V / ground side, because the
> circuit you are connecting to, can't tell whether it is a
> short to ground, or whether it is a low impedance
> output at zero volts.

Very Correct. The only time my circuit has an issue is if the 0.0V is
high impedance or even "open circuit" (not connected to ground at
all). If as you said, it is shorted to ground or low impedance, my
circuit works fine. So if this is how gate signals work, then I'm good
to go.

I think my confusion lies in not knowing about the 0V output of a
v-tigger indicating that there's no key being pressed down. Should it
be low impedance, high impedance, shorted to ground or open-circuit? I
know I'm talking from complete lack of experience (since I don't have
something that outputs v-trigger to be able to test with my meter), it
just seems to me like there are more than one way to show "0V" as I
mentioned above, and I'd like to make sure that my little box that
outputs a gate signal does it properly and consistent with other
synths, and that my other circuit responds to it properly.

Mike

On 2/21/07, Paul Perry <pfperry at melbpc.org.au> wrote:
> The problem isn't at the 0.0 V / ground side, because the
> circuit you are connecting to, can't tell whether it is a
> short to ground, or whether it is a low impedance
> output at zero volts.
>
> At the OTHER end......
> say you take the gate input to a MS20.
> When there is NO input to it from the external world, then
> it is holding itself up to a certain voltage by a pullup resistor.
>
> And it is easy to turn it on, by either shorting (hence the name S-trig)
> or by applying zero volts (same effect).
>
> But how to apply "no connection" to it from logic?
> Forunately, sending say 10V + to it, doesn't appear to hurt it.
>
> paul perry Melbourne Australia
>
> ----- Original Message -----
> From: "Mike Beauchamp" <mikebeauchamp at gmail.com>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Thursday, February 22, 2007 2:00 PM
> Subject: [sdiy] Gate outputs.. 0v or ground?
>
>
> > I have a simple question about gate inputs, but no hardware to quickly
> check...
> >
> > When a gate output (or v-trigger) is LOW, it's at 0 V right? Does that
> > mean it is "open circuit", or grounded, or somewhere inbetween? If
> > it's inbetween, what is the resistance to gnd?
> >
> > I'm building a super-simple VCO and I want it to be able to respond to
> > a gate signal to tell it when to actually output audio. I'm also
> > working on a really simple switch that can output the gate signal, and
> > I don't know if I should be grounding the output when the signal is
> > LOW, or just leaving it open circuit, or having some resistance to
> > ground. I'm also wondering if maybe I should be buffering my gate
> > output?
> >
> > The way my VCO works right now, it responds to a gate signal that is
> > >2V for HIGH and GND or around 100K resistance to gnd for LOW. If I
> > leave the gate input open circuted, the VCO assumes gate is also HIGH.
> > So you can see how if standard gate signals go from example 5V HIGH
> > and open-circuit LOW, my VCO won't make a distinction.
> >
> >  Thanks in advance..
> > Mike
> >
> >
> > --
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> 3:19 PM
> >
> >
>
>


--
Mike Beauchamp
Cross Canada Project: http://mikebeauchamp.com/crosscanada
Personal: http://mikebeauchamp.com
Business: http://therevox.com
Windsor News: http://windsorinb.relyon.ca


-- 
Mike Beauchamp
Cross Canada Project: http://mikebeauchamp.com/crosscanada
Personal: http://mikebeauchamp.com
Business: http://therevox.com
Windsor News: http://windsorinb.relyon.ca