Stand-alone temperature sensor

[knuth 29]

I intend to install a temperature sensor to trigger a fan when the room temperature is too high. I have looked at several options, but none seems fully satisfactory:

1. Using a multisensor like the Aeotec 6: Too bulky. I want to tuck the device in behind the fan with just the sensor tip visible. Besides, I don't need motion, humidity, and light - only a single temperature.
2. Connecting an external temp. sensor to my room thermostat (HeatIt Z-wave, aka Multireg): Won't work, as the thermostat seemingly cannot be configured to have an external sensor without using it to control the heat.
3. Buying a small dedicated single channel z-wave temp. sensor: There does not appear to be such a product on the market. I have seen humidity+temperature, light+temperature, and humidity/water+temperature, but no dedicated temperature sensor
4. Using a spare channel on one of my Fibaro RGBW dimmer for temperature input: Would have been a good solution, except my dimmers are more than 10 meters away from the fan. 

The best remaining option seems to be:

5. A temperature sensor attached to a Fibaro Universal Binary Sensor. The UBS needs DC power, which I don't have near the fan. A power supply (transformer/rectifier) adds complexity and bulkiness, so I would have to use a battery. It seems a waste to have a unit with four inputs and use only one, but at least it seems workable.

 

Questions:

What type of temperature sensor will be suitable in the last case (#5)? And what type of battery? Please be specific, based on your own experience with the Fibaro Universal Binary Sensor..

Does anyone know of a device as described in option #3, small enough to tuck away with the fan? 

[wpeeters 30]

@knuth

A fibaro door sensor with temp sensor attached? It"s battery operated and rather cheap if you can find some older ones.

[petergebruers 1,265]

I agree with @wpeeters regarding the older D/W sensor + DS18B20. Or UBS + DS18B20 + power supply... Or a real thermostat, like:

 

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I'm a fan of thermostat's for temperature control (pun intended). That's what they are for, and they are autonomous.

[knuth 29]

Not a bad idea @wpeeters . Saves me the job of soldering together a sensor, the universal binary and a battery connection. It is not small enough to fit inside the fan housing, but I will consider putting it on top of the nearest window. And to Fibaro: Removing the magnetic switch from the door sensor and reducing the size of the housing gives you a new product rather effortlessly: the Fibaro Temperature Dot?

Any other ideas out there?

Edited April 25, 2018 by knuth

[petergebruers 1,265]

5 minutes ago, knuth said:

the universal binary and a battery connection.

I hate to say it... The UBS cannot run on a battery. It drains a 9 V battery in less than 24 hours.

[knuth 29]

That's what this user forum is for! Thanks, @petergebruers, for keeping me out of trouble. Makes me wonder why, though. The door sensor shouldn't be all that different, and I expect that to have a much longer battery life.

[petergebruers 1,265]

Just now, knuth said:

The door sensor shouldn't be all that different, and I expect that to have a much longer battery life.

Z-Wave modules come in two basic types (little white lie to simplify things) - battery operated or mains operated. A mains operated device is "always on" and can relay messages for other nodes, so it cannot go in low power mode. So the UBS becomes an active part of your mesh routing. The D/W sensor does not do that... Some devices, like Aeotec MS6 determine power mode at inclusion time. So they can act as repeater or not (low power). But to change type, you have to exclude and include again.

[knuth 29]

Makes sense. I learn something every day.

[petergebruers 1,265]

4 minutes ago, knuth said:

Makes sense. I learn something every day.

I like your positive attitude. And I learn something every day, but I think I also forget something. I cannot remember... 

 

Edited April 25, 2018 by petergebruers

[wpeeters 30]

@knuth, I like your idea about the the Fibaro Temperature Dot very much

The advantage of the door sensor also is that the battery will operate for a long time I think because the (door) sensor is not doing anything.

In the screenshot below, you can see the 'garagedeur' doorsensor historical battery status.
The 'tempBathroom' is the same doorsensor but only in use as a temperature probe (don't ask why it's only 95% since the beginning  , I'm sure it should be 100%)

 

[knuth 29]

@wpeeters Your Garagedeur sensor battery seems to have risen from the (half) dead for a short while - around Easter??  How appropriate!  Joking aside, I see your point, which tells me that my Temperature Dot should be able to retain its battery for a long time. The temperature sensor you have attached to your door sensor, is that a Fibaro DS18B20 or third party?

[wpeeters 30]

my own mistake. A terrible mistake. I synchronized HC2 and HCL instead of doing an update to make a new device visible in my HC2. Sychronizing is changing all device IDs apparently. So, the peak in the graph is the value of another sensor at that moment. Lessons learned:-)

[knuth 29]

Update: Option 2 in my initial post, connecting an external sensor to a thermostat, may work after all. The Z-TRM2 thermostat allows for an external room sensor, even when temperature control is based on the floor sensor only. The external temperature is available for use in a scene to control the fan, as intended. And no batteries involved!