Controlling Temperature using a Touchscreen

Pick the Temperature control for the air conditioner template.

By default, this widget writes a number to a variable (give the instance a system variable as a target). You can then use that variable to talk to BMS systems (via BACnet/TPI) or in your own sequences.

Note: The variable works both ways. If BACnet, TPI, or a sequence changes the system variable the instance is linked to, that change will also show up as an updated value on the touchscreen.

Default behaviour:

• Value 0 = 15°C
• Each button press adds 0.5°C (so 1 = 15.5°C, 2 = 16°C, etc.)

Want to change this? Go to the widget's number display settings. There are three major settings that control it:

• Resolution – how precise the value is. 10⁻¹ means steps of 0.1 (1 decimal place).
• Increment – how many "resolution steps" each button press adds. Default is 5, so 5 × 0.1 = 0.5°C per press. If you set it to 10, you'd get 1°C per press.
• Offset – the starting value at 0, measured in resolution steps. Default is 150, so 150 × 0.1 = 15°C starting point. To start at 18°C instead, set offset to 180.

You can also modify the units by changing the Label field

Example: whole-number Celsius values

If you want the variable to just show whole degrees (e.g., 18, 19, 20...):

• Resolution = 10⁰ (1)
• Offset = 0
• Increment = 1

Each press now adds exactly 1°C, starting from 0.

Example: half-degree steps starting at 20°C

Say the customer wants the temperature to start at 20°C and go up in 0.5°C steps.

• Resolution = 10⁻¹ (0.1) — needed for 1 decimal place
• Offset = 200 (200 × 0.1 = 20°C starting point)
• Increment = 5 (5 × 0.1 = 0.5°C per press)

So value 0 = 20°C, value 1 = 20.5°C, value 2 = 21°C, and so on.

 

Example: whole-degree Fahrenheit, starting at 60°F

Say the customer wants the variable to write whole Fahrenheit values, starting at 60°F, going up 1°F per press.

• Resolution = 10⁰ (1) — whole numbers, no decimals
• Offset = 60 (60 × 1 = 60°F starting point)
• Increment = 1 (1 × 1 = 1°F per press)
• Label = °F

So value 0 = 60°F, value 1 = 61°F, value 2 = 62°F, and so on.

Targeting

Go to your system variable page, create a system variable, give it a name (Temperature, for example)

The variable number in this case is 4

Set the Touchscreen target

Once this is committed to the touchscreen, the system variables you've selected become readable and writable over BACnet, exposed as Analog Value points starting at point number 336.

So system variable 0 = AV 336, system variable 1 = AV 337, and so on.

Any change to the value — no matter where it comes from — should update everywhere else. This includes:

• Right-clicking the system variable in the system variable view and setting a value
• Pressing the touchscreen
• Using YABE or another BACnet client to change the value

If you wish to control DALI devices, whilst this guide will not have full instructions, the general process is to create a system variable change trigger and then run a sequence which operates on the values of the system variable

Troubleshooting

The value is jumping in larger / smaller jumps than expected

Check the temperature display resolution, increment and the individual up and down control increments in their Action configurations.

For example, customer sets the value to be decremented by 14, possibly misinterpreting the value to be a minimum or maximum.  Value gets multiplied by increment in main temperature display, producing unexpected results.