Water Backup System

[TerryJC]

Referring to the previous discussions here viewtopic.php?p=5830#p5830 and here viewtopic.php?t=322, I have produced a new Overall System Configuration Diagram that shows the way that Penri's idea will be implemented:

Overall_System_Configuration_V12.png (290.4 KiB) Viewed 216 times

In the diagram, I have re-used the numbers for the Valve and the Pump, because we would never have both solutions at that location.

Please let me know if you see anything wrong with what i have done.

[Penri]

Terry

Looks good to be, the only thing I need to check is where the solenoid valve is most easily plumbed back into the system.
I’ve probably commence work on the pump / by-pass valve configuration during this coming week.

Given the head of steam the guys doing the plumbing have got up we might even get to implement the gazebo water circuit soon.

[TerryJC]

Penri,

I'm going to miss the self-imposed deadline that I set myself earlier in the week. The new Valve is working from a hardware standpoint and passes the hardware Unit Tests. However, I'm struggling on the software side, see viewtopic.php?p=5955#p5955.
As soon as I've found out the problem, I'll repost here.

[Penri]

Terry

I don’t have all the bits required to plumb the pump and valve in yet.
Hopefully they will arrive this coming week.
BTW I built the pump SSR earlier today.
Penri

[Penri]

Circuit diagram of Up-stream pump control SSR attached.

Note: as currently built control is active Lo with no built in pull up on the control line, I need to correct this to ensure that if disconnected it fails safe, ie pump off.

Up-stream pump control v01.pdf

(18.95 KiB) Downloaded 33 times

Terry, do I need to build in a power up safe circuit to ensure the pump remains off when the control SAC is powering up?

[TerryJC]

Terry, do I need to build in a power up safe circuit to ensure the pump remains off when the control SAC is powering up?

I'm not sure about this. In theory all GPIO Pins default to inputs until set as outputs. However, I'm not too sure because the state of the GPIO Pins may be indeterminate during boot up. What did you do for the Main and Butts Pumps?

I'll ask the question on the RPi Forums later this morning.

[Penri]

No start up circuit was put into the Main and Butts Pump circuit and that works fine, so I’ve probably answered my own question.

BTW I realised after posting the comment about adding a pull up that the led / dropper resistor does that job for us.

[TerryJC]

Penri,

There is a difference between the Sump and the Backup Pump. If the Main or Butts Pumps came on briefly it wouldn't matter. This is slightly different in that the Pump could be short-circuited by the Valve.

I'm not convinced that the led / dropper resistor does actually do that job for us in the corner-case of boot-up. I've no real doubt that it would, but if the GPIO Pin drove out a high momentarily, the led / dropper resistor wouldn't help.

I'll still ask the question.

[TerryJC]

I've had no meaningful replies to my query on the RPi Forums, but the GPIO Spec says:

Power-on states
All GPIO pins revert to general-purpose inputs on power-on reset. The default pull states are also applied, which are detailed in the alternate function table in the ARM peripherals datasheet. Most GPIOs have a default pull applied.

Clearly once the boot up is complete and the logic has settled, that will be the state of the pins. However, is there a transitory period during which the pins could drive high? I suspect that it would hardly matter because the hardware reset would probably end within nanoseconds.

I don't think the pull states are relevant, because they only apply to inputs.

What do you think Penri?

[TerryJC]

I have some final fettling to do and the Gate Valve will be ready to deliver to WMT or to your home Penri. What would you prefer?