On 2007-02-18 09:59 +1100, Laurie Biddulph wrote:
with an op amp in voltage follower mode ?
V+ ^
|
|
+--o | |
| \ | _ |
< \ | | -_ |
R2 > o--+--|- -_ |
< | _>--+--o OUT
| --|+ _-
+--o | |_-
| |
< ===
R3 >
<
|
|
V- v
dividers instead of a single 8-tap voltage divider as show above.
Otherwise adjusting one voltage would upset the others.
V+ ^
|
<
VR1 ><--o
< \
| \
V- v \
o-- (To output buffer)
V+ ^
|
<
VR2 ><--o
<
|
V- v
Check this for inspiration :
http://www.wiseguysynth.com/larry/jlh-831/831.htm
--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
Do not use this account for regular correspondence.
See the URL above for contact information.
> From: "Andrew" <dumpstatic@...>Or perhaps more simply just buffer the output of a voltage divider
>
> > I would like to have a Rotary knob that would select between
> > eight specific voltages (to come out of the rotary to a jack).
> > The voltages would *not* have to be exact, maybe like within
> > 0.5 volts (+ or -) of the intended voltage.
> >
> > Could I do this by supplying +10v to eight different
> > resistors, and connecting the other end of each resistor to
> > the eight inputs of the rotary knob? (and then the output of
> > the rotary to a jack) Assuming I get the right resistor for
> > each specific voltage I want, would this work?
>
> If the resistors are connected in series with each being a
> calculated value then you will have a series of voltages as
> required. You will need to be wary of what you are connecting to
> as the impedance of that circuit could well upset the balance of
> your series divider network and thus change the values. Use high
> tolerance resistors to get accurate and stable voltages.
>
> A better approach would be to use an adjustable voltage
> regulator with a series of switched resistors (or trimpots) in
> the ADJ leg of the circuit. The output will be far more stable
> and, if trimmers are used, can be easily adjusted to any range
> of voltages desired. Have a look at the datasheet for the LM317L
> which shows not only switchable output voltages but also
> `digitally selected' switchable outputs.
with an op amp in voltage follower mode ?
V+ ^
|
|
>R1 <
>| ___________
+--o | |
| \ | _ |
< \ | | -_ |
R2 > o--+--|- -_ |
< | _>--+--o OUT
| --|+ _-
+--o | |_-
| |
< ===
R3 >
<
|
|
V- v
> > I suppose I could use resistor trimmers or even potentiometersSure but then you would have to do it with 8 separate voltage
> > instead of resistors for a more adjustable setup?
dividers instead of a single 8-tap voltage divider as show above.
Otherwise adjusting one voltage would upset the others.
V+ ^
|
<
VR1 ><--o
< \
| \
V- v \
o-- (To output buffer)
V+ ^
|
<
VR2 ><--o
<
|
V- v
Check this for inspiration :
http://www.wiseguysynth.com/larry/jlh-831/831.htm
--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
Do not use this account for regular correspondence.
See the URL above for contact information.