💬 Battery Powered Sensors

[evb]

@Yveaux It is not a aluminium door frame, but a PVC door frame (plastic).
The problem is that my gateway is in the extension of the brick wall, about 15m away in the garage at the backyard. So I have a 5m brick wall between de node and the gateway :-(
This means that the reliability of the connection is not good, so I had to place a repeater node between them.

[evb]

@canique no, the purpose of the node is to know when the door is locked by the bolt, not only closed. What you see are simply 2 battery springs and the bolt of the lock closes the contact.
I can move the node more upwards the door frame (and I will do it if the radio connection is still not reliable with the repeater).
In order to preserve domestic peace, I placed the nodes in the door frame, invisible when the door is closed: no visible dangling wires and no visible boxes.

Maybe an idea for a MK3 version of your board as wide as the RFM69HW ;-)

[tssk]

Hello

I created battery powered node running on 2x 1.5V AA batteries with DC-DC step up booster. But the step up booster makes audible noise (very tiny beeping) when the radio is transmitting.

It is this step up booster https://www.laskarduino.cz/step-up-boost-menic-s-me2108-33v-480ma/

Is there any way to solve it?

Thanks

Tomas

[TheoL]

@tssk First things that comes to my mind is that you might draw too much power (but no expert) did you measure it?

[canique]

@tssk There is a name for this noise: it is called "coil whine". In German "Spulenfiepen". It stems from the inductor - I wouldn't know any way to get rid of it.
My mainboard or power supply on my PC creates similar noise when the CPU goes in certain doze modes.

[BearWithBeard]

@tssk I heard that people got rid of or at least reduced the coil whine by coating the windings of an audible inductor with non-conductive materials like epoxy resin or even hot glue to reduce the vibrations.

Of course, I woudn't mess with expensive PC hardware, but I guess there's not much to loose with a cheap boost module like this.

[tssk]

Thanks all for the response.

@BearWithBeard I will start googling about such solution.

Do you think using different step up booster might help? Could someone recommend something?

[canique]

I am biased since I run that website but I can recommend https://www.canique.com/boost
I've never heard it making noise.

[tssk]

@canique Thanks for the recommendation if I do not find fix for the model I am using I will consider buying it.

I will try to hot glue the side with the coil as I found on some pages. Any ideas / warnings? :)

[zboblamont]

@tssk Most of these boosters have a grounded backplane, perhaps trying to re-orientate the inductor so the backplane acts a shield to direct RF may be an option to try ?
If the noise in on the power line I've heard of some managing to block it with a VR circuit if the voltage drop is acceptable, but never tried it.

[tssk]

@zboblamont It is not electrical noise but audio noise I can hear. Sorry if I use improper terms.

[zboblamont]

@tssk My misconception.

[skywatch]

@tssk If the item is not going to be too hot then hot melted candle wax dripped over the coils will probably help.

[tssk]

So I used hot glue and it is better. Now I can hear the squeal only when I put my ear directly to the PCB. Thanks for the tips.

@TheoL I have no idea how to measure that.

I noticed that when the radio is transmitting the LED on the Arduino Pro Mini (not the power one) starts blinking very tiny. I still plan to remove the power LED and voltage regulator from the Arduino.

[mfalkvidd]

@tssk the led blinks because it is connected to the same pin as the SCK pin used by the nrf24.

[tssk]

@mfalkvidd You are right :) I did not know that.

SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication, which, although provided by the underlying hardware, is not currently included in the Arduino language.
LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off.

https://www.arduino.cc/en/pmwiki.php?n=Main/ArduinoBoardProMini

Should I remove the LED to save power? Or it is marginal?

[mfalkvidd]

@tssk it is marginal

[tssk]

@mfalkvidd Thanks.

[tssk]

Hello

I would like to ask for help with passive battery powered node I created with following components:

• Arduino pro mini 8MHz - voltage regulator and power LED removed
• SX1276 based 868MHz LoRa radio
• BME680 sensor
• DC-DC 3.3V step-up booster

I created a battery measuring circuit according to scheme on this page ( https://www.mysensors.org/build/battery ).

The problem is the two fresh new AA batteries lasted less than 14 days and stopped when the circuit measured 36%.

2x1.5V AA Aerocell following start and end values:

09.02.2021 16:45 102% (start) : 1.610V and 1.610V
22.02.2021 04:15 36% (end) : 1.001V and -0.150V

The node code is sleeping for 6 minutes between each sensing and sending data.

sleep(180000);

14 days seems very short to me. Is that normal? Is there something I can to make it last longer?

Thanks

[mfalkvidd]

@tssk could you post your sketch? Some things that could draw power:

• bme not turned off properly when sleeping the node
• lora transmits can take a long time, depending on which settings are used

Which booster are you using? A good booster will use almost no power when the node is sleeping. A bad booster will consume almost as much as if the node was not sleeping, so the performance of the booster will make a huge difference.