Non Resol Lan

[mrfreon]

Hi all, just joined your group after reading the article on Non Resol
adaptors and thought I would give you my experience. I already had a
Hexin HXSP-2108e adaptor and thought I would give it a try, after
trying many different methods of connection on the various pins (T
+,T-,R+,R-,Ground, 9v input) I was receiving only corrupt data, very
similar to other members who posted. I even made up the suggested
interface on the Resol documentation and got the same corrupt data
through the serial port. In desperation I returned to the Hexin Lan
adaptor and after making an error in connecting it up got the correct
data. I had modified my adaptor slightly to give me a 9v feed out on
the 9v pin rather than using it as an input, and accidently connected
one of the wires to that pin and one of the R pins. Now I don't
understand electronics too much but proceeded to connect the adptor
wires to the 2 T pins and used a resistor to link from the 9v to the T
+ pin, everything works fine and through a process of trial and error
found around 60 ohms worked best for me. It seems that maybe the
Resol, units aren't happy if the bus voltage drops too low? any ideas?
Well now everything seems to work with the unit, although as other
members I'm using a virtual serial port to communicate, but it seems I
can do the paremetrisation as well as far as I can test, I have a new
BX model and they have not updated the software for it yet to do
parametrisation, but if I set it to another unit it tries to read
although reports mostly errors but does report some readings
correctly, so it seems I have 2 way communication. Hopefully someone
may be able to give more detail on why it needs the voltage boost, all
I could find was that you can terminate to earth or a voltage on 485,
beyond that I got a bit lost. This may help others who are using non
Resol units to get theirs up and running without forking out for the
resol unit. If any electronics wizard can fully explain my findings,
I'm all ears.

[Mark Richards]

" Now I don't
understand electronics too much but proceeded to connect the adptor
wires to the 2 T pins and used a resistor to link from the 9v to the T
+ pin"

Throwing volts on the vBus may produce some interesting results.  There's a protective diode that if you're fortunate will take care of things, but there's only so much manufacturers can do to prevent folks from turning expensive controls into paperweights.  RESOL publishes a nice document, available through this group, that describes the interface.  May be best to read first, then tinker.

It is possible to read a VBUS directly on an RS485 circuit.  I've built a passive adapter that provides sufficient level shifting such that the VBUS toggles between +/-4 volts  with respect to reference ground which keeps RS485 happy as to differential (VBUS sits at around 8V DC).  As the VBUS does not reference earth ground, a virtual ground is made possible.  Other methods are available but I am not certain they're all that reliable.

The best solution which provides for 2-way communications is to use RESOL's adapters or roll your own.

/m

[Kaptainkriz]

Mark,
Do you have a link to, or description of, what you built? My system
is finally up and running and now I'm starting to look at
instrumenting it.
-john

On Feb 21, 7:19 pm, Mark Richards <m...@solarwave.com> wrote:
> I've built
> a passive adapter that provides sufficient level shifting such that the
> VBUS toggles between +/-4 volts  with respect to reference ground which
> keeps RS485 happy as to differential (VBUS sits at around 8V DC).  As
> the VBUS does not reference earth ground, a virtual ground is made
> possible.  Other methods are available but I am not certain they're all
> that reliable.

> /m

[Mark Richards]

On 2/21/2011 19:58, Kaptainkriz wrote:

Mark,
Do you have a link to, or description of, what you built?  My system
is finally up and running and now I'm starting to look at
instrumenting it.
-john

With a VOM across the VBUS, identify + and -.  Then inject 4 volts (reference from DC ground) into the - side.  Attach - to the RS485 B input; + to A.  The voltage divider is 680 ohms and 330 ohms in series with +12 volts.  Hasn't fried anything yet.. but no warranties.

Properly inverted, you should see the buss default to -4v and jump to +4v for each assertion of a bit.  Since RS485 detects a difference across A and B, this provides plenty of that.

/m

[John and April Kriz]

Like this?  Also, id the ground referenced to either device anywhere....ground on the 485?

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