Re: Q: 5V<->12V level conversion

And now for something completely different!

http://members.optushome.com.au/adambradley/electronics/LevelConverter
/V12/LevelConverter-v12-ajb.jpg

Possible?
TIA!
Adam

--- In opendiag@yahoogroups.com, "Adam Bradley" <adam_j_bradley@y...>
wrote:
> Possibly the final at
>
http://members.optushome.com.au/adambradley/electronics/LevelConverter
> /V10/
>
> Adam
>
> --- In opendiag@yahoogroups.com, "Adam Bradley"
<adam_j_bradley@y...>
> wrote:
> > Updated schematic (with simulation pictures!) at
> >
>
http://members.optushome.com.au/adambradley/electronics/LevelConverter
> > /V2/
> >
> > Please keep those comments rolling in!
> >
> > Adam
> >
> > --- In opendiag@yahoogroups.com, "Adam Bradley"
> <adam_j_bradley@y...>
> > wrote:
> > > Henrik,
> > >
> > > I've uploaded a couple of images of my schematic in which a TTL
> > high
> > > and low (5v and GND) are injected into the circuit.
> > >
> > > Once again the two files are in
> > > http://groups.yahoo.com/group/opendiag/files/AJB/
> > >
> > > and called
> > >
> > > 5V connected to TTL Tx.jpg
> > > 5V disconnected from TTL Tx.jpg
> > >
> > > The multimeter reading is taken from the K line.
> > >
> > > Any ideas how this works?
> > > :)
> > >
> > > Adam
> > >
> > > --- In opendiag@yahoogroups.com, "alfatok" <hi.johnsson@t...>
> wrote:
> > > > --- In opendiag@yahoogroups.com, "Adam Bradley"
> > > <adam_j_bradley@y...>
> > > > wrote:
> > > > > Henrik,
> > > > >
> > > > > After a bit of bashing about I've made a couple of changes
> that
> > > make
> > > > > the circuit a little better. Rather than a voltage
divider,
> > I've
> > > > > used a pull down resistor to tag the voltage at either 0V
or
> 5V
> > > > > irrespective of the input voltage (almost anyhow!).
> > > > >
> > > > > Can you have a look at
> > > > >
> > >
> >
>
http://members.optushome.com.au/adambradley/electronics/LevelConverter
> > > > > /LevelConverter-v7d-cnv-candidate.jpg
> > > > >
> > > > > Also, if I want to optoisolate this circuit (in both
> > directions)
> > > is
> > > > > all that is required to add two opto's on both the Rx and
Tx
> > > lines?
> > > > >
> > > > > and let me know what you think?
> > > > > Thanks!
> > > > > Adam
> > > > >
> > > >
> > > > Took a while to grasp, but the only way I can make sense of
> that
> > is
> > > if
> > > > you have turned the Q1 symbol upside down. The battery
symbols
> are
> > > > definitely turned the wrong way. If my suspicion about Q1 is
> > > correct,
> > > > then it will act as an inverter, high on K-line gives low on
Rx
> > > which
> > > > is not the way the original design worked and not the way Tx
> > works.
> > > > But maybe I'm wrong. As I said, I'm not very good at this
stuff.
> > > >
> > > > Actually, if you're going to run the entire design powered
from
> > the
> > > > electrical system in the car, opto isolation might not be
such
> a
> > big
> > > > issue. If you look at the design I pointed out in my previous
> post
> > > > you'll see that it takes two opto isolators and you will
> probably
> > > need
> > > > to have two transistors on the K-line side. You must make
sure
> the
> > > > uController Tx line is capable of driving the LED in the opto
> > > > isolator, otherwise it must be buffered. You also have to
> > consider
> > > the
> > > > polarity of the signals. Most schematics that you'll find for
> this
> > > > kind of interface are designed to be connected to a serial
port
> > on a
> > > > PC where the signals are inverted compared to what you get
> > straight
> > > > out of the UART. Those designs invert polarity of the data
> going
> > in
> > > > both directions, your design probably shouldn't.
> > > >
> > > > /Henrik

 
Received on Fri Oct 24 00:55:29 2003