Tutorial 8 — logic and conditions

Part 2 — Tutorials. Continues the project from Tutorial 7.

What you will build

A re-triggerable corridor light — every movement restarts the countdown
A dimmer that remembers its last level
A "holiday mode" the whole system can check
Wires that fire only when conditions are met

This is the chapter where iDM3 stops being a switch board and starts being a system.

12.1 The system's own devices

Four things live inside the central unit rather than on the bus. They exist only in your project, they cost nothing, and they are what you build logic out of.

Device

Holds

How many

Range

Timer

elapsed time

0.0 s to 24 h

Counter

a count

0 to 4 294 967 295 (32-bit)

System bit

one true/false

500

—

System integer

one number

500

—

All four are defined in Managers → System manager, each on its own tab. Each tab shows how many you have used against the maximum.

All four work as actor and consumer. A wire can start a timer; when that timer elapses it becomes the actor of another wire. That is how behaviour chains together without any code.

12.2 Timers — a re-triggerable corridor light

The staircase light from Tutorial 2 had a flaw: pressing the button again mid-cycle did nothing, because Digital_Impulse_ON ignores an output that is already on. Real corridor lighting should restart the countdown every time it sees movement.

A timer does exactly that, because Timer start on a running timer restarts it.

Define the timer

Managers → System manager → Timers tab.
Click +. The Details panel becomes editable.
Fill in:
- Name: CORRIDOR_TIMER
- Timer value: 00:02:00 — how long until it elapses
- Tick interval: leave at default unless you need repeating ticks
- Automatic reset — see the table below
- Automatic stop — likewise
Click ✓.

Autoreset and autostop decide what the timer does when it reaches its value:

Autoreset

Autostop

Behaviour

off

keeps running past the value, counting up

off

stops at the value and stays there

off

returns to zero and keeps running — a repeating cycle

returns to zero and stops — the one-shot you usually want

For a corridor light: both on.

Timers have two actions:

Action

Fires

Timer tick

every tick interval, while running

Timer elapsed

once, when the timer value is reached

Wire it

Two wires — one to start the timer, one to act when it finishes.

Wire 1 — motion starts the timer and the light:

Design tab → place an input icon → Connect it to a motion sensor input (or a spare button) → name it Corridor motion.
Function tab → Add connection → drag Corridor motion → Stair light.
Wire manager → name it Corridor on → +: Action Digital IN switch ON, User function DIGITAL_ON.
Add connection → drag Corridor motion → the timer object. (Dragging from the central unit icon opens Select devices to create wires — pick CORRIDOR_TIMER.)
Wire manager → name it Corridor timer start → +: Action Digital IN switch ON, User function TIMER_START.

Wire 2 — the timer switches the light off:

Add connection → drag the timer → Stair light.
Wire manager → name it Corridor off → +: Action Timer elapsed, User function DIGITAL_OFF.
Close, save, upload.

Every movement restarts the two minutes. The light only goes out two minutes after the last movement — which is what people actually want.

The timer functions: TIMER_START, TIMER_STOP, TIMER_RESET, plus Timer copy.

12.3 Counters

A counter counts events and can act when it reaches a number.

System manager → Counters tab → +.
Fill in Name — DOOR_COUNT.
Set Counter value to the number you want to act on. Setting it also tells the system that the Counter reached value action has a target.
Tick automatic reset to zero the counter each time it reaches that value.
✓.

Action

Fires

Counter increase

on increment

Counter decrease

on decrement

Counter reached value

when it hits Counter value

Counter changed value

on any change

Functions: COUNTER_VALUE_INCREMENT, COUNTER_VALUE_DECREMENT, COUNTER_VALUE_RESET, plus Counter set value and Counter copy.

Wire a door contact's Digital IN switch ON → COUNTER_VALUE_INCREMENT, and the counter's Counter reached value → whatever should happen every tenth time.

12.4 System bits — remembering a state

A system bit is one true/false the whole project can read and write. It is how the system remembers something that is not a physical device: holiday mode is on, the alarm is armed, nobody is home.

System manager → System bits tab → +.
Fill in the Name — HOLIDAY_MODE.
Tick non volatile so the value survives a central-unit reboot.

Field

Purpose

Name

how you refer to it

non volatile

keep the value across a CU restart

Alias:

an alternative name for third-party integration

Add to iNELS 3 export:

expose it to external systems

Read only:

external systems may read but not write it

The last three matter only when something outside iNELS talks to the system — Chapter 24.

Tick "non volatile" for anything a person set deliberately. Holiday mode surviving a power cut is the difference between a system that feels reliable and one that does not.

Actions: System bit true, System bit false. Functions: System bit set bit, System bit null bit.

Wire holiday mode

Place a button, name it Holiday button.
Add connection → drag it → the HOLIDAY_MODE system bit.
Wire manager → +: Action Long down, User function a System bit set bit you define in Function manager.
Add another: Action Short down, User function System bit null bit.

Now anything in the project can check holiday mode — which is what §12.6 is about.

12.5 System integers — a dimmer that remembers

A system integer stores a number: a temperature, a brightness level, a mode.

This solves the problem from Tutorial 3 — ANALOG_SWITCH only moves between 0 % and 100 %, so a dimmer never returns to the level you left it at.

System manager → System integers tab → +.
Name: LIVING_ROOM_LEVEL, tick non volatile.

Each system integer also shows an Address, an index starting from 0, and the same Alias, Add to iNELS 3 export and Read only options as system bits.

The pattern:

When

Function

Effect

the light is switched off

SYSTEM_INTEGER_COPY_VALUE

save the current level into the integer

the light is switched on

Analog set level sourced from the integer

restore it

Actions available on a system integer: SysInt_Change, SysInt_ChangeUp, SysInt_ChangeDown. Functions: SYSTEM_INTEGER_INCREMENT, SYSTEM_INTEGER_DECREMENT, SYSTEM_INTEGER_COPY_VALUE, SYSTEM_INTEGER_RESET, plus Sys int set.

System integers are also how you build a multi-press scene selector: increment the integer on each press, and use conditions to act differently for each value.

12.6 Conditions — rules that fire only sometimes

Everything so far fires every time. Conditions gate a wire so it only acts when something is true.

You met the theory in Chapter 2. Here is the practice.

Add one

Wire manager → select a wire → select a function → edit (pencil).
In the Wire function window, find the Conditions section.
Click Add condition, then choose the kind:

Button

Compares

Restriction value

a device's state against a number you type

Restriction object

a device's state against another device's state

A condition row appears with four parts:
- which device — a key opens the device selector; you can also pick the wire's own actor or consumer
- which input/output on it
- the operator — = <> > >= < <=
- the value

Worked examples

Goal

Condition

only if the light is currently off

Restriction value — that output = OFF

only if it is colder than 18 °C

Restriction value — the sensor < 18

only if the dimmer is at full

Restriction value — that output = 100

only when holiday mode is off

Restriction value — HOLIDAY_MODE = OFF

only if two outputs agree

Restriction object — output A = output B

For digital devices, ON and OFF are the two values. For analog, use the percentage: = 100 means full, = 0 means off. Temperature conditions use the measured value — > 14.15 is a valid condition.

Combining conditions

Add a second condition and a Relation dropdown appears:

Relation

Fires when

AND (A)

both are true

OR (O)

at least one is true

For nested logic, Combination groups conditions so they are evaluated as a unit.

"In this case is allowed only AND operation" — or the OR equivalent — means the structure you are building supports only one relation. Restructure, or use Combination.

Put it to work

Make the outside light from Tutorial 7 respect holiday mode:

Wire manager → Outside light — dusk to dawn → edit the DIGITAL_ON function.
Add condition → Restriction value → HOLIDAY_MODE = OFF.
OK, save, upload.

Now dusk only lights the garden when somebody is home.

12.7 Choosing the right tool

You need

Use

A delay after an event

timer

A delay you can restart

timer (not an impulse)

To count events

counter

To remember a yes/no

system bit

To remember a number

system integer

To act at a clock time

program (Ch. 11)

To gate an existing rule

condition

What you learned

Timers, counters, system bits and system integers live in the CU and are both actor and consumer
Timer start restarts a running timer — that is what makes corridor lighting work
Autoreset + autostop both on gives the usual one-shot timer
System bits remember states; tick non volatile so they survive a reboot
Restriction value compares against a number, Restriction object against another device
Conditions combine with AND / OR, and nest with Combination

Try this before moving on

Make the corridor light dim rather than switch off, so it never goes fully dark at night.
Count how many times the front door opens per day and reset the counter at midnight with a periodical program.
Add HOLIDAY_MODE = OFF as a condition on your heating boost button.

Next: Chapter 13 — Tutorial 9: alarms and messaging.

Also on this wiki

Understanding Bits and Integers in iNELS Design Manager

PreviousTutorial 7 — time control

NextTutorial 9 — alarms and messaging