Trouble understanding the Logic Actuator

Troubleshooting
1

I am using the Logic Actuator to drive a Mock Pin, I wanted to use the logic operators to only turn on the glycol pump when any one of the tank valves are open (these are driven by the usual Sensor-Setpoint-PID-PWM-Actuator-PIN chain of blocks). I cant figure out why a logical (False & True) is resolving to TRUE.

Grateful for any insights.

Cheers

Blocks
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Logic1

2

Could you please export your blocks? (admin page -> spark service)

Edit: it looks like there’s a minor display bug in the widget (the red circles don’t turn green).

Otherwise, the widget suggests that FV-1 Cool Actuator is currently ON, and FV-3 Cool Actuator is currently OFF.

From your description, I would expect the comparisons to both be “Measured state == ON”, and the expression to be a|b. (result is true if FV-1 is ON or FV-3 is ON)

You are currently evaluating “FV1 is ON and FV-3 is OFF”.

3

brewblox-blocks-spark-fv-control.json (10.3 KB)

blocks attached:
Yes agree with your description of logic behaviour. Clearly I would need an OR expression for my use-case, however the logic did not make sense to me, so I tried the AND instead and it still did not make sense. Result should be FALSE if a is ON AND b is OFF, not TRUE (or ON as in the Actuator display)

What am i not getting here?

4

You definitely want to reason while using the “measured state == ON” for both actuators. This makes it simpler. By using “measured state == OFF”, you invert the result (true becomes false for this actuator, and vice versa).

If you use a|b, then you get the the following behavior:

  • OFF + OFF => false
  • ON + OFF => true
  • OFF + ON => true
  • ON + ON => true

If you use a&b, this becomes:

  • OFF + OFF => false
  • ON + OFF => false
  • OFF + ON => false
  • ON + ON => true

Logical OR can be described as “one or more conditions must be true”.
Logical AND means “all conditions must be true”.

5

You’re saying what I am saying. But the brewblox result is different from what we are both saying LogicActuator and I am wondering if you can tell me why. Please see the screen grab.
Thanks

6

Note that you have 2 different actuators.
If both a and b would use the same actuator the expression would indeed be always false.

The red dots should show the state, but as Bob said there is a bug causing them to show red incorrectly here.

The equation also shows the state of each expression, and it seems to work in my test.

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The expression you want is probably this:

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