# Thread: P&F Scheduler

1. hansvanzijp Gast

## P&F Scheduler

Is it possible, in PFS, to use a calculated value (math var) as the offset for a schedule, type Time Relative? If so, how?
Example:
Controlling a heater, the heater must be switched on a calculated time before shift starts. The pre-start time depends on outside temperature.

2. ## Re: P&F Scheduler

the offset for a relative time or absolute time (e.g. from shift start) is always static. Based on this offset, and the shift start, the switching points are calculated.

However you may be able to include the outside temperature in another way.

Outside temperature is quite variable. In the early morning hours (before sunrise) it is usually colder than in the middle of the night.

Based on the coldest outside temperature (the longest time the heater must be switched on before shift start) you create a switching point. At the switching point, you set an internal variable instead of the variable to turn on the heating. This internal variable (1) and the outside temperature are multiplied in a mathematics variable. The mathematics variable is calculated by a trigger event. (6.50)

The mathematics variable has several limits, each with a different delay. The coldest temperature limit (e.g. "Minimum -21" has a delay of 0 seconds). The second coldest limit (e.g. Minimum -18) has a delay of 60 seconds, the next limit Minimum -14 has a delay of 120 seconds, and so on.

This possible solution may not be the best for your situation. With some more information, another solution may be possible as well.

3. ## Re: P&F Scheduler

the PFS user events in this case, do not allow a negative time offset prior to shift begin.

4. hansvanzijp Gast

## Re: P&F Scheduler

Hello Mark,

Thanks for your help. We also thought about a solution like this, disadvantage is that it is difficult to explain it to the end-user. When the offset could be calculated, the end user can just adjust the time the shift starts (in a picture type PFS), the calculations take care about the pre-heating.
With the suggested solution when shift start changes we must also change the other switching point to for example 2 hours before shift start.
Maybe this is something for the wish list for 6.51?

5. ## Re: P&F Scheduler

Hallo Hans,

Nog even de beste wensen, voor ik het vergeet!

Originally Posted by hansvanzijp

Thanks for your help. We also thought about a solution like this, disadvantage is that it is difficult to explain it to the end-user. When the offset could be calculated, the end user can just adjust the time the shift starts (in a picture type PFS), the calculations take care about the pre-heating.
With the suggested solution when shift start changes we must also change the other switching point to for example 2 hours before shift start.
Maybe this is something for the wish list for 6.51?
I can definitely throw this into the group for discussion.

A time offset based on a variable is very flexible. With each change of the variable value, it should calculate a new absolute switching point.

It should be very carefully defined what happens if due to a value change, the switching point is suddenly in the past. (Should or should it not be repeated) Or what should happen, when the value is I-BIT (e.g. due to a communication interruption to the temperature sensor) Or what happens when the PC time changes (either externally, or due to daylight savings)

6. hansvanzijp Gast

## Re: P&F Scheduler

Hallo Mark,

Ook voor jou/jullie de beste wensen. Zeker lekker weer Down-Under? Wij zitten al een tijdje in de sneeuw.

Also in this case the exceptions will be more work to implement as the rule, but I think it will be a useful function. For this project we will use a workaround, thanks for your help.

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