How to power my sensors in a rental?

[mirodin]

Hey guys,

the Mrs and I will move to a new place in April. After checking out the new apartment I started to worry about how to migrate my existing MySensors setup when it comes to powering my nodes.

Some background:

• Right now most sensors are powered via smartphone chargers which was working great even though having all those plugs triggered my OCD
• Our new place is a rental so any "destructive" solution is impossible
• Since it is an older building there are very limited sockets which makes my current setup somewhat unfeasible as it would pretty much clog all sockets (old place 5+ sockets per room, new place 2 (3 tops))

After thinking about this for some time I came up with a solution that (at least to me) sonds feasible: I would get myself a 48V power supply (to limit voltage drop) and connect it to one plug in our new living room (center of the apartment). Then I could get some cable ducts and create a star topology to every room in the apartment. Every node would get its own buck converter to reduce 48V to 5V/3.3V respectively.

Does this sound like a solution that could work? Am I barking up the wrong tree? Any recommendations and hints are very much appreciated!

Cheers

[Yveaux]

@mirodin What kind of sensors do you plan to run? Can they be battery powered?

[mirodin]

@Yveaux I had battery powered sensors in the past and some of my outside sensors still run on battery. But since I am a very lazy busy man and always forget changing batteries I migrated my setup over to plugs.

This is my current setup, numbers in brackets will be estimated number for new place:

• Door/Window 4x (6x)
• Temp/Hum sensors for every room 3x (5x)
• Relays for blinds 6x (11x)
• more to come...

My thinking was since for those blind relays I would need plugs anyway a central power source would make things easier for me. 48 V would give me enough headroom to expand my setup further without having to fight voltage drop or pumping huge amps.

[Yveaux]

@mirodin said in How to power my sensors in a rental?:

My thinking was since for those blind relays I would need plugs anyway a central power source would make things easier for me. 48 V would give me enough headroom to expand my setup further without having to fight voltage drop or pumping huge amps.

Relays don't need continuous power per se (e.g. use a bistable relay) but running the the radio in Rx continuously requires a plugged power source.

For the door/window/temp/hum sensors I would still go for battery power. Using decent quality batteries these nodes should run for years easily on a single set.

[mirodin]

@Yveaux said in How to power my sensors in a rental?:

For the door/window/temp/hum sensors I would still go for battery power. Using decent quality batteries these nodes should run for years easily on a single set.

So with future expansion of my network in mind would it not be easier to get a sufficient setup from the get go rather than put battery powered sensors "everywhere"? My first sensors (window/door) took one battery set (2x AA) down within 2-4 months. Over time this would cause a substantial number of battery usage. Sorry if this might seem silly, I just started 8 months ago so there are a lot of things about MySensors I do not know yet but I thought getting rid of the "energy problem" would make thinks easier.

Relays don't need continuous power per se (e.g. use a bistable relay) but running the the radio in Rx continuously requires a plugged power source.

I did not know that, will check them out. But my receivers will still have to be online all the time if I am not mistaken?

[Yveaux]

@mirodin If you follow the suggestions given by https://www.mysensors.org/build/battery and some scattered around the forum you will easily reach many years of battery power for a reed sensor or a temp/hum node.

I understood you have to rebuild your setup anyway, so instead of wiring everything I personally would only wire the actuator nodes, and battery power the sensor nodes.
But in the end it's your choice; if you feel more confident with wiring everything up then go that way.

But my receivers will still have to be online all the time if I am not mistaken?

That is correct

[mirodin]

@Yveaux Thank you for your patience with me nagging about that! I will give battery sensors another try and since I need to power the blinds anyways I will be able to upgrade my sensors if I am not happy with the battery setup.

[zboblamont]

@mirodin If you were looking to centralise and distribute power to the Nodes you could run telemetry in the same duct, messy but your choice, radio is much neater, and surprisingly frugal if set up correctly.

"My first sensors (window/door) took one battery set (2x AA) within 2-4 months" means something is wrong with your Node or switch, as @Yveaux said you should easily last over a year and it is easy enough to monitor battery condition and warn when getting low. eg My gas meter (reed) is still on 2.69v on 2xAA after two years of radioing in a a reading every 10 litres - that's an average of 600 reed triggers per day in winter just for heating.

[eelledge]

@mirodin If they are simple low power draining, you could use the very cheap battery pack phone chargers. The ones you put AA batteries in. For more power hunger sensors, you could look at the rechargeable battery packs for phones. Double side tape to hold things in place? Just thinking off the top of my head.

[mirodin]

@zboblamont That is impressive, I thought more than 6 months is somewhat of a black magic trick due to the energy used to send stuff. I think my main mistake was using normally closed reed switches back than. Not knowing that there are normally open switches as well. How does this "every 10 liters" thing work using a reed switch? Am I misunderstanding something?

@eelledge That are some interesting ideas, I will definitely dig into this area.

[zboblamont]

@mirodin It's a reed but not as in your case door switches, but it hopefully illustrated the point the number of reed contacts is HUGE compared to how often your door normally opens/closes.
NO v NC is unlikely to be the mistake, possibly the pullup resistor circuit was draining too much or inducing multiple sends as the contact was not debounced.
Your take on radio energy loss is misplaced, the radio burst is so rapid it draws little energy. eg I initially programmed the Gas Node to report every 5 triggers, now it's every trigger, no hit on battery life.

I don't have the skills (or patience) to design such an energy efficient Node hence it was bought in, but most here have built similarly frugal DIY Nodes, and a wealth of info and advice is here on the forum.
The 10 litres is down to the Gas meter default, the reed is thereby magnetically triggered on 0.01m3, in this case drawing the Interrupt LOW.

In your case CHANGE would be the trigger for OPEN/CLOSED otherwise sleep, you only need check the pin state for verification and figure out where your energy was disappearing to.

[Nca78]

@mirodin said in How to power my sensors in a rental?:

using normally closed reed switches

You can "convert" those by reverting the orientation of the magnet on your door, then adding another magnet (weaker or further away) inside the node enclosure to keep the reed switch closed when you open the door. When the door is closed the reversed magnet on the door will open the reed switch.

To do even better you can use :

• reed switches with 3 leads that work as both normally opened and normally closed switches, and wire them to the 2 interrupt pins. I used that on my first nodes and managed to get reeeeaaaally long battery life on a simple CR2032. When door status changes the node is woken up then you set pin low and current could run only a very short time, you send the message with new status then you activate the other interrupt pin and go back to sleep https://www.aliexpress.com/item/33028519094.html
• if you're not afraid with SMD there are some ultra low power hall switches, using less than 1uA of current like the DRV5032.