Fallback vs. Set

[dleary]

I've consulted the Comprehensive Reference Manual, and have read what it has to say about the "Fallback" and "Set" commands.

"Fallback" sounds pretty straight forward - if the energy bar looses communication with the base module, the outlet is turned on or off, depending on the Fallback line.

"Set," however, is confusing me. The Comprehensive Reference Manual states,
"The Set statement is used to establish the starting point for this outlet's register state for this run through the program - it initializes the outlet."

Can someone elaborate on that statement (in layman's terms, please)? What is meant by "register state," and "it initializes the outlet?" "Initializing the outlet" seems an awful lot like the functionality of the Fallback command.

[RussM]

Think of Set as the default condition of that outlet. You then use other statements to alter the state of the outlet as needed.


Here's a really simple example for a return pump:

Set ON
If FeedA 000 Then OFF

The default condition of the outlet is ON, 7/24, except when shut off by a fed cycle

And another for lighting:

Set OFF

If Time 08:00 to 19:00 Then ON

[dleary]

I'm still confused between the two. Can you look at the 4 return pump examples below, and tell me what each would do?

Set OFF
If FeedA 000 Then OFF

vs.

Fallback OFF
Set ON
If Feed A 000 Then Off

vs.

Fallback ON
Set OFF
If FeedA 000 Then OFF

vs.

Fallback ON
Set ON
If FeedA 000 Then OFF

?

[HeneryH]

Fallback is for when the EB loses contact with the controller, it goes to that state. This should be a failsafe mode if for instance your controller falls into the sump. Which pumps would you want on, etc. If your heaters are set with an internal thermostat as a backup, you may want the heater outlet failsafe to be ON. Maybe the lights OFF.

On the Set, I think of the rules as a state machine. Give it a starting point via a Set then rules that may change the state away from that starting point.

[RussM]

You have a good understanding of Fallback already it seems. It is not a regular program statement - it does nothing under normal conditions; it only kicks in as an "emergency" feature upon loss on Aquabus communications.

Set is, to me, the easiest normal program statement of them all. It simply says "turn the outlet on or off, or use the XXX profile. It establishes the normal desired operating state of an outlet, which can then be changed by subsequent conditional program statements (If statements) as desired.

Set ON
If Temp > 82.0 Then OFF

This program will cause the outlet to be on all of the time - unless the temp exceeds 82, then the outlet will get turned off. When the temp drops to 82.0 or less, the Set ON will be the only TRUE statement, so the outlet will get turned back on.

[LobsterOfJustice]

Set OFF
If FeedA 000 Then OFF

[Return pump is always off]

vs.

Fallback OFF
Set ON
If Feed A 000 Then Off

[Return pump is on 24/7 except when feed A is activated. If the controller dies or otherwise loses control of the outlet, the return pump will be off]

vs.

Fallback ON
Set OFF
If FeedA 000 Then OFF

[The return pump is always off. If the controller dies or otherwise loses control of the outlet, the return pump will be on]


vs.

Fallback ON
Set ON
If FeedA 000 Then OFF

[Pump is on 24/7 except when Feed A is activated. If the controller dies or otherwise loses control of the outlet, the return pump will be on. This is the most practical program for a return pump.]

[LobsterOfJustice]

I think the set statement might make more sense if you look at some more complicated programming. Every second, the apex runs through the lines of code in an outlet in sequence. Set gives it a starting point. For example, if you program lights as:

If Time 08:00 to 20:00 then ON

There is nothing to turn the lights OFF after 20:00... the apex isn't smart enough to understand what you meant without you explicitly saying it.

Set OFF
If Time 08:00 to 20:00 then ON

This means every second the outlet starts in the OFF state (not physically, but just imagine it this way), but the next line turns the outlet ON if the current time is between the two values.

Or consider a topoff pump:

If Switch1 CLOSED then ON

This program would turn the pump on when the switch was closed, but doesnt know when to turn it off.

Set OFF
If Switch1 CLOSED then ON

This tells the outlet to be OFF unless Switch1 is CLOSED.

Hopefully that makes sense.

[dleary]

Thanks for those replies - they did help clear up my confusion between the two!