Re: 0-5vdc converted to 0-10vdc on the cheap

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<davemucha@j...> wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>

wrote:

> > Fred Smith wrote:
> >
> > >I have a control signal that varies from 0-5vdc and want to use

it

> on
> > >another device that needs 0-10vdc. Fast control response is not
> > >required.
> > >
> > >Available power is 5vdc and 12vdc both regulated.
> > >
> > >A solution that fits home-hobbyists budgets is required.
> > >
> > >What kinds of solutions can be used?
> > >
> > >An LM317 variable voltage regulator might be a possible solution
> > >(certainly cheap).
> > >
> > >Is there a ready to go solution already available?
> > >
> > >
> > I think this would be difficult with just a regulator chip. An

OP

> Amp
> > is the tool of choice. Use a rail-to-rail op amp if you really
> need to
> > go all the way to zero. Or, power the op amp from +12 and -5 or -
> 12 V,
> > so it can deliver zero volts when needed.
> >
> > The circuit would be to connect the 0-5 V input to the + input of
> the
> > op amp. Connect a 10 K resistor from the output to the - input.
> > Connect another 10K resistor from the - input to the signal

ground.

> > The output will now swing from 0-10 V as the input goes from 0-5.
> > You may need a small capacitor, say 100 pF in parallel from output
> > to - input to stabilize the op amp.
> >
> > Jon
>
> If you can get the rail to rail from Radio Shack, you can use a

small

> perf board and get it put together in short order.
>
> If not, a 15 volt transformer with center tap would offer the

ability

> to get enough voltage spread for a 741 op-amp. it uses the

negative

> to get below zero and Forrest Mimms has a small booklet on op-amps
> with circuits at radio shack.
>
> still all fit on a perf board from RS
>
> Dave

Use an LM324 quad (14 PIN) or LM358 (8 pin) dual single supply op
amp. Hook it up in a simple non-inverting configuration (or use two
of the amps both inverting for extra buffering). Configure one of
the op amps to have a 2X gain (better to put in a small pot to adjust
the exact gain). Google for the app notes or the spec sheet on the
chips. There is also an opportunity to put in a level of filtering
to change the frequency response of the circuit to exclude noise or
interference from getting into the output. For precision
applications you may have to provide an offset trim but in most case
you don't need that and the circuit is a chip and 3 resistors.

The 741 needs + and - supply while the 324 series can run from +5 to
+ 30 VDC supply. You only need about .6 volt more supply than the
output so the +12 would be perfect. Since gain is not dependent on
supply voltage then even unregulated DC will work.

Tom C
Old analog/digital engineer