'B-Model' System Interfacing

[TerryJC]

The prototype hardware has now been running well for over 4 months with the only problems due to water ingress into the Wireless Routers (not to be part of the final installation anyway) and someone switching the mains off at the end of the Summer season....

Since then several key decisions have been made; some in these forums, some during face-to-face discussions at the WMT and some in occasional emails. In addition, further development of a number of devices has taken place. In summary, these key decisions and developments include:

1. The redesign of the Hall-Effect Level Sensor (see viewtopic.php?f=15&t=111, (details coming soon)).
2. The development of the Gate Valve Electronics (see viewtopic.php?f=15&t=103).

As a result, a completely new Interfacing scheme is needed, which for the purposes of this discussion, I have christened the B-Model.

At this point, I have completed an updated version of the Mechanical Layout (see viewtopic.php?f=15&t=106) and will shortly be posting a circuit diagram and sufficient information to build the system in this Topic.

The main thing that I currently need to complete the documentation is some details on the final design of the Hall-Effect Probe and agreement on the mechanical layout.

[TerryJC]

Penri,

I'm just finishing the first draft of the Interfacing Circuit Diagram and have a couple of queries before I publish it for review:

1. What combinations of the green screw terminals do you have for making the connections to the Veroboard? With the Gate Valve, you provided 10-ways; made up of two triple and two double blocks. Only 8 of these were needed. The current design for the Master & Butts Pis Interfacing needs 14 terminals, but that could grow as we add sensors. (We could of course piggy back Veroboards to carry several sets of blocks.)
2. Can you think of anything that I might have forgotten from the following list:
   1. Two terminals for power in (+12 V and return).
   2. Two terminals for power out to the sensor (+12 V and return).
   3. Two terminals each for SSRs.
   4. Two terminals for the Float Switch.
   5. Four terminals for the Magnetic Probe.

In the above list, I have made some assumptions about what we want to do:

1. We don't want to put more than one wire into each terminal.
2. We will need a discrete 0 V line for each of the SSRs, although we could reduce the terminations needed by commoning up in the wiring.
3. We won't need a 0 V wire for the Magnetic Probe inputs, because it is commoned to the incoming PSU 0 V in the probe.

Any thoughts?

[Penri]

Terry

I have 14 off of the 10 way terminal blocks, all made up of 2off 3way and 2off 2way section, in stock. We can mix and match as required.

In 2b. if by sensor do you mean the Magnetic Probe, that's correct and assumption c is right too.
In 2c. the twin SSR box we have installed (in the big green box), needs 4 connection: SSR1 control, SSR2 control, +12V and 0V. The +12V is used for manual control of the SSRs, the +12V and 0V are common to both SSRs.

I can see from the above that the I/F can cater for the Sump set up:

• 1off depth probe

• 2off SSRs

Wendy House Butts:

• 1off depth probe

• 1off float switch

• SSR for Valve H bridge pump

Wendy Stage Butts and any other remote Butts:

• 1off depth probe

• 1off float switch

I think you are correct.

Penri

[TerryJC]

I have 14 off of the 10 way terminal blocks, all made up of 2off 3way and 2off 2way section, in stock. We can mix and match as required.

OK. As I suspected.

In 2c. the twin SSR box we have installed (in the big green box), needs 4 connection: SSR1 control, SSR2 control, +12V and 0V. The +12V is used for manual control of the SSRs, the +12V and 0V are common to both SSRs.

So the four terminals that I have provided will only cater for the two control lines, but If I re-use the two return lines as a second 12 V supply for the SSR box, it won't need any more terminals?

I can see from the above that the I/F can cater for the Sump set up:

• 1off depth probe

• 2off SSRs

Yes. We can add another four discrete outputs and five discrete inputs, but we would have to add A/D boards to add more analogue Probes.

Wendy House Butts:

• 1off depth probe

• 1off float switch

• SSR for Valve H bridge pump

Yes. As above.

Wendy Stage Butts and any other remote Butts:

• 1off depth probe

• 1off float switch

Hmmm. I hadn't thought about the Stage Butts. Until you mentioned this, I assumed that any sensors and/or control would be done from the Wendy Street Butts Pi. We would either have to add another A/D Board, as above, or add another Pi, which would require a full interfacing solution.

Either way, it doesn't really affect the basic design of the Interfacing, so I'll post the first version of the design shortly.

[TerryJC]

Attached to this post is the first draft Master & Remote Pis Interfacing Circuit. It includes all of the features and details that I think we need and used in conjunction with the Mechanical Layout Drawings, (viewtopic.php?f=15&t=106#p1690), should allow us to build all of the Monitoring/Control Pi Assemblies with only minor changes to cater for a specific location.

Still to be done is the layout on Sheet 3 for the Veroboard to carry the Terminal Blocks and Hex Buffer chips. It will be much easier to produce that when the first build has been completed.

Please let me know if you have any comments.

[TerryJC]

After this morning's partial refresh of the installed hardware (see viewtopic.php?f=13&p=1714#p1714), Penri and I agreed the tasks that needed to be completed in the immediate future, in order to progress this work. This includes:

1. Penri will use the information in the Mechanical Drawings (see viewtopic.php?f=15&t=106#p1690 to produce a baseboard/box for the modules. During this work he will look into:
   1. Re-arranging the modules slightly (compared to the prototype Gate Valve) to provide a little more room for the wiring.
   2. Look into making the baseboard/box wide enough to accommodate up to 14 terminations.
2. Penri will make available some of the green terminations and appropriately sized Veroboard.
3. I will progress the build of the first Interfacing equipment (probably for the Sump Pi) and test it here in my Workshop.
4. We will then try an installation of one of the new Interfacing assemblies, before building a second one for the Wendy Street Butts.

The above work will be interleaved with installation of the Gate Valve, when we have sorted out everything we need.

(Penri, I forgot to ask this morning, but I will also need a slack handful of the DuPont terminations for the build. I have a crimp tool.)

[Penri]

Terry

I'll take the DuPont terminations (plus crimp tool), terminal blocks and Vero board to WMT tomorrow, I'll be there until around 12:30.

If possible can you drop off for me one each the modules that need to be accommodated on the baseboard so I can re-check my dimensioning, I don't need the RPi or the ethernet dongle.

Thanks

Penri

[TerryJC]

Penri,

I should be able to get to WMT by around 11 ish.

[TerryJC]

After quite few trials and tribulations (my original design didn't work properly), we've now got a B-Model Interfacing circuit diagram that fulfils all three requirements: SSR control, new Magnetic Probe reading and monitoring of the Float Switch state. New software is needed for the new Magnetic Probe (it will be called HallEffectProbe2() in the software framework, but the current hardware build appears to be ready to use.

Attached to this posting is the latest circuit diagram and associated build documentation. I expect the documentation might change as we refine the board layout etc, but the circuit shouldn't (assuming no unexpected issues).

I the attached drawing, the build notes are provided, together with the system layout and details of the wiring.

All comments welcome.

[TerryJC]

Attached is the version of the circuit diagram and assembly instructions that were used to build the unit currently being installed at the WMT.