Posts for the month of December 2014

Holiday tips for sensor events

We get a lot of questions on how to use sensors in events. I would like to take the opportunity to clear out some common misconceptions.

First of all, when you add a new sensor trigger, it will never trigger right away. Let's say you add a sensor trigger that triggers below 10 degrees and your sensor is currently 5 degrees. You sensor must first go above 10 degrees once before it will ever trigger.

The sensor trigger and sensor condition has an option to set a temperature equal to a temperature. In reality this is rarly the case. Let's say you have a sensor trigger that equals 20 degrees. When your sensor goes from 19 to 21 degrees it might never be exactly equal to 20 degrees. One sensor report might send 19.9 to TellStick Net and the next 20.2. In this example the trigger will never trigger.

If you run into trouble and need support, we are here for you. To help us help you there are some things you can do to give us the required information to follow your events. If you want help with your events, please include this in your report:

  • The name of the sensor you are using
  • The name of the event that didn't work
  • A time where the event should have triggered but didn't. This is the most important one.

This is an example how your report could be:
Hi Telldus
I have some troubles with my event xxx. The sensor zzz is used to turn my heater on when the temperature is below xx degrees. Last night at about XX:YY the temperature dropped below xx degrees but my heater didn't start. Could you help me figure out what is wrong?

Another common way to use the events together with sensors is to control a heater. Some of the questions we get is how to add events to control the heating at a certain level during the day and another during the night. I will try to explain how to do this and why.

In this example we have one temperature sensor and one TellStick controlled heater. We would like to have the temperature at around 20 degrees during the day (08:00-23:00) and 15 degrees during the night.

First, start by creating our first event. We call this "Day - Heater ON". We need a sensor trigger that triggers on the temperature. Add a sensor trigger that triggers when the temperature goes below 19 degrees. This event is only used during the day so we will add a time condition between 08:00 and 23:00

Next we need an event to turn off the the heater ("Day - Heater OFF"). This is similar to our previous event:
Trigger: Sensor above 21 degrees
Condition: Time between 08:00 and 23:00
Action: Turn heater off

The reason we do not set the sensors trigger level to 20 degrees is because the triggers rearm boundary. You can read more on this in our previous blog entry.

For the night we add two similar events: Night - Heater ON
Trigger: Sensor below 14 degrees
Condition: Time between 23:00 and 08:00
Action: Turn heater on

Night - Heater OFF
Trigger: Sensor above 16 degrees
Condition: Time between 23:00 and 08:00
Action: Turn heater off

So far this is quite simple. The problem arrives if the temperature is not within the interval when we are switching from day to night or vice versa. Lets say the temperature is 17 degrees at 07:59. The heater will be off due to the event "Night - Heater OFF". When the time is 08:01 the heater will still be switched off since there is nothing to turn it on again. The temperature will continue to drop and the heater will not be turned off. To solve this we need to add another trigger and condition to our events.

In the event "Day - Heater ON" add a time trigger at 08:01 and a sensor condition on the sensor must be below 19 degrees. The event should now look like this: Trigger: Sensor below 19 degrees OR Time is 08:01
Condition: Time between 08:00 and 23:00 AND Sensor is below 19 degrees
Action: Turn heater on

Now this event will take care of both scenarios. We need to add the same to the night. Event "Night - Heater OFF"
Trigger: Sensor above 16 degrees OR Time is 23:01
Condition: Time between 23:00 and 08:00 AND Sensor is above 16 degrees
Action: Turn heater off

To use AND in conditions you need a  Pro account. If you don't have a Pro account it is still possible to achieve the same results, but you need two extra events. For non-Pro users. Your setup should be configured like this:
Event: "Day - Heater ON 1/2"
Trigger: Sensor below 19 degrees
Condition: Time between 08:00 and 23:00
Action: Turn heater on

Event: "Day - Heater ON 2/2"
Trigger: Time is 08:01
Condition: Sensor is below 19 degrees
Action: Turn heater on

Event: "Day - Heater OFF" Trigger: Sensor above 21 degrees
Condition: Time between 08:00 and 23:00
Action: Turn heater off

Event: "Night - Heater ON"
Trigger: Sensor below 14 degrees
Condition: Time between 23:00 and 08:00
Action: Turn heater on

Event: "Night - Heater OFF 1/2"
Trigger: Sensor above 16 degrees
Condition: Time between 23:00 and 08:00
Action: Turn heater off

Event: "Night - Heater OFF 2/2" Trigger: Time is 23:01
Condition: Sensor is above 16 degrees
Action: Turn heater off