Sensor & Control Assy Development and Build

[TerryJC]

The old Master & Remote Pi Interface has been rechristened Sensor & Control Assy (I'm calling it SAC for short). The reasoning behind the name change is that the devices aren't just an interface and they include the Pi (eg the Pi and the interfacing are part of the complete assembly). I think the new name makes more sense, in that it describes exactly what it does.

Anyway, we needed to modify the installed Master & Remote Pi Interfaces to accommodate the new Max/Min Float Switch and also to improve the reliability by changing the wiring techniques to overcome the problems that we had with the Chinese crimps. To this end, I have built a completely new SAC which incorporates all the changes so that we can start to pull the old devices out to upgrade them. It has been agreed that this will replace the device in the Wendy Butts area. The device removed from there will then be modified in due course to allow us to upgrade the rest of the deployed devices.

I have modified the documentation in parallel with this work and I will be uploading the latest versions of the Sensor & Control Assy Composite Document and also the Installation Spec, which has been updated as errors came to light.

[hamishmb]

Sounds good Hopefully replacing it will give us a hint at what's been going on with the probe readings at that site.

[TerryJC]

This post is to publish the details of the further upgraded version of the SAC. This upgrade is to accommodate the additional Hall Effect Probes and Composite Float Switches that will be located at the Lady Hanham Butts Groups. With the modifications described below and shown in the attached Circuit Diagram, the SAC will provide:

1. An additional two A/D Converters so that the device can cater for Hall Effect Probes in each of Butts Groups G1, G2 and G3.
2. An additional four channels of level shifting to cater for Composite Float Switches in each of the above Butts Groups.

This is achieved (I hope) with the minimum number of changes to the existing design by the addition of a second Veroboard mounted as a mezzanine board on top of the single Veroboard in the current design. The main changes needed to the current Veroboard design will be:

1. Six additional Vero Pins to carry power and signals between the two boards.
2. Four additional Vero Pins to carry signals between the Veroboard and the Pi.
3. Some additional wire links on the Main Veroboard, so that the spare buffer/translators on the 74HC4050D IC can be utilised.

The new Mezzanine Veroboard will include mostly links between a new Terminal Block designated TB2 and Vero Pins to route signals to and from the Main Veroboard and the Pi. There will also be four new Pull-up Resistors.

I would appreciate any comments on the attached circuit Diagram. My next task is to design the Mezzanine Veroboard, which should be fairly easy, since there is not much on it and I have a clean slate. A more difficult task will be to shoe-horn the additions onto the Main Veroboard and that may entail making it bigger and moving things around a bit. Before I do that, I'd like to see any comments that might be raised

[TerryJC]

While thinking about the design of the Mezzanine Veroboard, I spotted a few mistakes and omissions so I've redone the circuit. I also realised that the layout didn't much lend itself to convenient wiring of the sensors, so I've re-arranged the circuit to rectify that.

See attached.

[Penri]

Will take a look later, had a quick look at v09 last night.

[Penri]

Afternoon Terry,

The only thing I can see you may want to look at in the V10 circuit is that you have the Hall-Effect Probe DC power feed for the standard configuration conditioned via a Low Pass Filter and the DC feed for the other two probes (G2 & G3) coming from the +12V supply before the filter. If you do change the configuration to supply all the probes from the filtered supply (and assuming you use one filter circuit) it would be worth rechecking the filter components to make sure they are still within acceptable operating parameters at the high current levels.

Some other things I noticed:
there are 3 "C" and "G" terminals on the standard configuration board
there are a,b,c, g, p & q is upper case on the Standard Configuration and in lower case on the Additions
the "OV(D) c" I/P on the Additions sheet is connected to "g" and "3V3 g" input is connected to c
the "ADDR" terminal of the lower ADS1115 is connected to the "SCL" line "q"
the "ADDR" connection does not appear on the Standard Configuration ADS1115

I understand that the ADS1115 devices will need to to be individually identified but without knowing what you're plan is I can only point out the things I notice without knowing whether they are right or wrong. I might be worth a small note on the circuit diagram to way "ADS1115 A" is address something and "ADS1115 B" is something else and so on.

When we install the SSR to control the matrix pump, it will get it control from the Wendy SAC, yes? if so would it be worth recording which SSR control line that would be on the Standard Configuration sheet.

Hope all that helps,

Penri

[TerryJC]

Penri,

Thanks for these comments. I'll produce V11 tomorrow afternoon.

The only susceptible component in the filter circuit is the inductor, which is made with 24 AWG wire. This seems to be good for 2 A, but I need to check the spec for the veroboard tracks and the wire links that I'll be using to route the current from the main board to the mezzanine.

[TerryJC]

Penri,

I've updated the circuit (see attached) and also produced the first draft of the Veroboard updates, which I'll post later.

The only thing I can see you may want to look at in the V10 circuit is that you have the Hall-Effect Probe DC power feed for the standard configuration conditioned via a Low Pass Filter and the DC feed for the other two probes (G2 & G3) coming from the +12V supply before the filter. If you do change the configuration to supply all the probes from the filtered supply (and assuming you use one filter circuit) it would be worth rechecking the filter components to make sure they are still within acceptable operating parameters at the high current levels.

The 12 V supply for the two Hall Effect probes is now drawn from the filtered side of the circuit. As mentioned earlier, I'm fairly comfortable with the current capacity of the circuit, my only uncertainty was the wiring and the Veroboard tracks. At the O/P of the filter on the main board, the current will split two ways, with one third going to the G1 probe (out of pins 3 & 4 on TB1) and the rest going to the mezzanine. When I run a standard SAC, my bench PSU delivers ~0.5 A, of which ~0.25 A goes to the Pi. This means that ~0.5 A will be delivered to the mezzanine (on pins e & f). I don't think that will cause any problems, but I will monitor it during initial testing. The Veroboard tracks are quite short and I'll use thick wire to link the I/P to the relevant pins on TB2.

there are 3 "C" and "G" terminals on the standard configuration board
there are a,b,c, g, p & q is upper case on the Standard Configuration and in lower case on the Additions
the "OV(D) c" I/P on the Additions sheet is connected to "g" and "3V3 g" input is connected to c

I've completely renumbered the Veropins on the mezzanine to make more sense when counting on the physical board.

the "ADDR" terminal of the lower ADS1115 is connected to the "SCL" line "q"
the "ADDR" connection does not appear on the Standard Configuration ADS1115

ADS1115_Fragment.png (79.82 KiB) Viewed 1279 times

I understand that the ADS1115 devices will need to to be individually identified but without knowing what you're plan is I can only point out the things I notice without knowing whether they are right or wrong. I might be worth a small note on the circuit diagram to way "ADS1115 A" is address something and "ADS1115 B" is something else and so on.

I've added the I2C address of the two additional devices on the circuit diagram of the mezzanine. Without any specific programming the address defaults to 0x48.

When we install the SSR to control the matrix pump, it will get it control from the Wendy SAC, yes? if so would it be worth recording which SSR control line that would be on the Standard Configuration sheet.

Actually, I've done the opposite. The SSRs will be used for different things at different locations:

1. At the Sump; for the Main and Butts pumps.
2. At the Wendy House; for the Matrix pump.
3. At the lady Hanham; the solenoid valve.
4. At the Gazebo; the soaker hose?

I have therefore not attempted to define the routing there. Much of this will eventually be in the updated Composite Document and we should also update the Overall System Configuration Diagram to show these things. Ultimately, we will have a User Manual which will cover the complete design.

[TerryJC]

I have completed the first draft of the Veroboard layout (attached) and this is what I will use to construct the Lady Hanham SAC. Past performance shows that I will identify more errors as I progress, so I have little doubt that this won't be the last version.

During the work to complete the Veroboard layout, I discovered some omissions on the circuit, so that has been updated again.

I now intend to design the additional wiring links needed for the assy and I will make some modifications to wire lengths for the standard SAC wiring based on the experience I had when building the upgraded Wendy Butts SAC.

[hamishmb]

Sounds like good work Terry