# ðŸ’¬ Battery Powered Sensors

• @sineverba yes, you're right. It looks a bit different but the connections are equivalent. Sorry for the confusion.

• @mfalkvidd no problem ! I can understand the difficult to understand schemas of other people do you nave btw somw idea for my issues and queation (if I can remove a caos, for example).... Thank you

• @sineverba sorry, I don't. I have no experience with the bare atmega.

• How about using rechargeable batteries instead of alkaline? They would be 1.2V instead of 1.5. vmax would be 2.8V ?

• @Oliviakrk
I use recheargeable. At full charge both are 2.74...
DHT22 at 2.74 doesn't read. It is rated for 3.3v - 6v

• @sineverba
Yes, so a stepup before DHT 22 is required. And it works...But..I have issues with measuring battery level.

``````int batteryPcnt = sensorValue / 10;
``````

Always gives something around 74-77%. Even if I use batteries straight of the charger (Panasonic/Sanyo Enelops, which are 1,3 -1,4V when taken of the charger)

• There is minor correction in the battery level measurement calculation. It should be `1.1 * (1 * 10^6 + 470 * 10^3) / (470 * 10^3) = 3.44V`

• @Oliviakrk Look in comments in the code

``````// 3.44/1023 = Volts per bit = 0.003363075
``````

if your batteries put out a total of 2.8V the voltage divider is set to use a Vmax of 3.44V (that suits the alkaline batteries), that is probably why. If you want you could change the voltage divider for a lower Vmax

• @sundberg84 To give you an update. I've changed from a dht22 sensor to a bme280 i2c sensor. The sensor is running off a4 and 5 and power is gotten directory from 2aa batteries. My original problem is gone in that it's working fine as a mysensors node. My issue though is when in sleep mode, i'm running at 1ma, when i would expect to be down in the low ua area. Any thoughts? The code i'm using is based off of this thread: https://forum.mysensors.org/topic/3816/bme280-temp-humidity-pressure-sensor/5

• @FatBeard I looked at the datasheet and you should expect only a couple of uA... not mA. I would first disconnect the sensor and make sure it's not the other setup that draws power. Did you remove led and volt. reg.?

If the sensor still draws power I would either try another one or power it from a digital pin and turn power off before sleep with LOW.

• @sundberg84 Thanks Sunberg, pretty much sorted now. It was the sensor, i changed libraries and it solved my problem. In theory i was using the forced read with both, but only the sparkfun bme280 library worked in reducing the power. To the best of my knowledge, i'm now running at 6ua most of the time with a 60ms (i timed from beginning to end of the loop method) jump to 1amp every three minutes to get a reading. It's difficult for me to capture the amps properly as when i put my uni-t digital multimeter into the circuit, the nrf stops working. Any thoughts on why that might be?

• 1 Amp is definitely a lot. I think it can't be a correct reading

• @FatBeard - as @gohan said - 1A can not be correct. Something is wrong.
If the radio does not work, and the sensors if fishy... I would disconnect it and run the radio/atmega only and fake a sensor value to send and see what happens.

• @sundberg84 @gohan. Apologies , that's a typo on my part. It jumps to 1ma do 60ms from 6ua. Which I'm happy with I think. My question was more how I can measure it properly. The multimeter seems to be effecting the circuit.

• This post is deleted!

• @FatBeard actually what you really need to measure is the sleep current as it is the state where the node will be spending all of its time. Where are you connecting the multimeter for measuring current?

• @gohan between positive end of one of the two aa batteries and where it enters circuit. If I start off by having battery connected, the release it slowly with the multimeter attached and without breaking circuit I get my 6ua. However after the timer runs out and the radio comes back on I'm stuck at 1ma. The radio at that point doesn't want to work and it doesn't return to 6ua

• @FatBeard the burden voltage of your multimeter might be too large, which would reduce the voltage to the atmega below its working level.
You're measuring current, so the meter must be in series with the power supply. It's not clear to me how you can remove the multimeter without breaking power to the atmega.

• You could try to add a booster to power the Arduino or change the multimeter

• Hi to all!
I have a issue reading of voltage on pin A0 of an ATMEGA 328 barebone mounted on a breadboard.

This is the image

The purple pin goes to A0.

The rail on the bottom coming direct from batteries, with a multimeter I read that they have 2.73V. On monitor serial, % of battery is about 1-2% and voltage reading is about... 0.004 and floating about 0.004 - 0.010 ....

Can I imagine an issue with pin A0 itself? I have about 10 Atmega spares and I will test another one... but thinking about this issue.

I did try also removing the 0.1uF cap, without any change.

The reading function is the same of this sketch.

Thank you very much!

• Hi guys, if your Arduino is equipped with an ATMega 328P then it could go down to 1.8V at lower frequencies like 1MHz (8MHz internal RC oscillator / 8 by default).
Or you can use the internal low power 128KHz RC osc eventually ...
It means you could power both the Arduino and the radio directly from the battery string and consume even less current.
Just wondering if anyone tried these cases so far?

• There have been some users that went that way but personally I am preferring to use a single AA LiFePo4 battery with standard voltages and clocks

• I am a newbie and have some thoughts about the battery level that I did not find in this forum.
The 8MHz 3.3V Arduino Pro Mini can handle down to roughly 2.8V.
If I have understood the calculations in the sketch correctly then the analog value of A0 is 1023 at 3.44V and 0 at 0V.
This means that at 2.8V the value is about 830 = 83% and under this, the Arduino stops working. Is this right?
If this is correct, I wonder if someone has changed the calculation in the sketch so that the battery percentage becomes 0 at 2.8V?
This would mean that the battery percentage becomes a more real value on the battery level.

• It's a simple percentage calculation that you can do it in the code

• @gohan Thanks for your reply, you can show me how the code should look.

• ``````void batM() //The battery calculations
{
delay(500);
// Battery monitoring reading
int sensorValue = analogRead(BATTERY_SENSE_PIN);
delay(500);

// Calculate the battery in %
float Vbat = sensorValue * VBAT_PER_BITS;
send(msgVBat.set(Vbat, 3));
int batteryPcnt = static_cast<int>(((Vbat - VMIN) / (VMAX - VMIN))*100.);
Serial.print("Battery percent: "); Serial.print(batteryPcnt); Serial.println(" %");

// Add it to array so we get an average of 3 (3x20min)
batArray[batLoop] = batteryPcnt;

if (batLoop > 2) {
batteryPcnt = (batArray[0] + batArray[1] + batArray[2] + batArray[3]);
batteryPcnt = batteryPcnt / 3;

if (batteryPcnt > 100) {
batteryPcnt = 100;
}

Serial.print("Battery Average (Send): "); Serial.print(batteryPcnt); Serial.println(" %");
sendBatteryLevel(batteryPcnt);
batLoop = 0;
}
else
{
batLoop++;
}
}
``````

This is the function I use, I just define the VMAX and VMIN in the beginning of sketch. The function calculates an average of 3 measurements before sending the value

• @gohan said in Battery Powered Sensors:
Hello, i didn't know why you add 4 measures (batarray) and you divide by 3 the sum .

• @tonnerre33 good catch! maybe it's an optimistic value

• I actually didn't look much at battery percentage, but I prefer looking at the voltage that gives me a better idea of how the battery is doing since I can log the values on a graph

• @magnusf It is important to know that the battery voltage is non linear in respect to how much juice left. Just search for "battery discharge curve" to see how much it depends on battery type, current and temperature. So calculating the percentage is actually meaningless unless You exactly know how much current your board sucks at what temperature and what type of battery You use.

• Instead of using "DC-DC Step Up Boost Module 5V" for a HBS, wouldnÂ´t it make sense to just use 2 AA batteries for the nano and 2 additional batteries (i.e. four in a row) for the HBS?

• What's the hbs?

• Same as on the motion example - HC-SR501, 4.5V- 12V.

• Maybe only a third Battery, as the HBS only needs 4.5V..

• To answer my own question: yes, it seems to work. Searched around and read a while, found this:
https://forum.mysensors.org/topic/6511/hc-sr501-3-3v-randomly-sends-tripped-when-radio-is-on/22
Best addition imho ,no need for step up / down.

• Hi,
I'm trying to build a Soil Moisture sensor with NiMh battery and solar panel as in another post. I use a stepup converter to 3.3V connected on the VCC of a pro-mini 3.3V. The sensor seems working when connected to FTDI USB device, ut once I remove the power from FTDI, no more communication. I measured the voltage on the output of the stepup which indicates 3.26V. Is it norml or a defective step-up ? And should I remove the regulator of the pro-mini as suggested above or not ? (in article above, it states the regulator is not necessary, but it doesn't say if pro-mini would still work if regulator remains there).
Thanks for your support

• @ricorico94 what does the debug output from the node and the gateway say?

What regulator are you using? Most regulators produce power that is too noisy to be usable by the nrf24 radio (you didn't state which radio you're using so I'm just guessing here, based on the most common problems). What capacitor(s) are you using after the regulator?

See https://forum.mysensors.org/topic/666/debug-faq-and-how-ask-for-help/ for the most common problems and how to diagnose them.

Also see https://www.mysensors.org/build/battery for more information about battery powered sensors.

• Hi,
As regulator I use a stepup like that one:
https://fr.aliexpress.com/item/DC-DC-0-8-3-3V-to-3-3V-Step-Up-Boost-Power-Module-For-Arduino/32819660926.html?spm=a2g0s.9042311.0.0.27426c37HEbdcz

I use a NRF24L01 as radio module following the connection guidelines from Mysensors. I did not add any capacitor to 3.3 and ground of the NRF24L01.
I connected the vO of the stepup to the VCC (the VCC between RX and GRD and not the RAW) of the arduino pro mini 3.3V as indicated in this post:https://forum.mysensors.org/topic/4045/solar-powered-soil-moisture-sensor
I use indeed a similar lamp with its small NiMh battery (1.2v) and its solar panel.
The NRF24L01 is connected on GRD (between RST and RAW) and on VCC (between A3 and RST). I hadn't put any capacitor.
I tried following your advice to add a 0.1uF ceramic capcitor between VCC (the one between RX and GRD) of pro mini and its ground, but apparently, I face same issue.
(I did not solder the capcitor yet, I only connected through the pins I usually use for the FTDI)

``````16 MCO:BGN:INIT NODE,CP=RNNNA---,VER=2.2.0
26 TSM:INIT
28 TSF:WUR:MS=0
34 TSM:INIT:TSP OK
36 TSF:SID:OK,ID=4
38 TSM:FPAR
75 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
2084 !TSM:FPAR:NO REPLY
2086 TSM:FPAR
2123 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
4130 !TSM:FPAR:NO REPLY
4132 TSM:FPAR
4169 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
6176 !TSM:FPAR:NO REPLY
6178 TSM:FPAR
6215 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
8222 !TSM:FPAR:FAIL
8224 TSM:FAIL:CNT=1
8226 TSM:FAIL:DIS
8228 TSF:TDI:TSL
18229 TSM:FAIL:RE-INIT
18231 TSM:INIT
18237 TSM:INIT:TSP OK
18241 TSF:SID:OK,ID=4
18243 TSM:FPAR
18280 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
20289 !TSM:FPAR:NO REPLY
20291 TSM:FPAR
20328 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
22337 !TSM:FPAR:NO REPLY
22339 TSM:FPAR
22376 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
24385 !TSM:FPAR:NO REPLY
24387 TSM:FPAR
24424 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
26433 !TSM:FPAR:FAIL
26435 TSM:FAIL:CNT=2
26437 TSM:FAIL:DIS
26439 TSF:TDI:TSL
36442 TSM:FAIL:RE-INIT
36444 TSM:INIT
36450 TSM:INIT:TSP OK
36454 TSF:SID:OK,ID=4
36456 TSM:FPAR
36493 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
38502 !TSM:FPAR:NO REPLY
38504 TSM:FPAR
38541 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
40550 !TSM:FPAR:NO REPLY
40552 TSM:FPAR
40589 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
42598 !TSM:FPAR:NO REPLY
42600 TSM:FPAR
42637 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
44646 !TSM:FPAR:FAIL
44648 TSM:FAIL:CNT=3
44650 TSM:FAIL:DIS
44652 TSF:TDI:TSL
54657 TSM:FAIL:RE-INIT
54659 TSM:INIT
54665 TSM:INIT:TSP OK
54669 TSF:SID:OK,ID=4
54671 TSM:FPAR
54708 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
56717 !TSM:FPAR:NO REPLY
56719 TSM:FPAR
56756 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
57493 TSF:MSG:READ,0-0-4,s=255,c=3,t=8,pt=1,l=1,sg=0:0
57499 TSF:MSG:FPAR OK,ID=0,D=1
58765 TSM:FPAR:OK
58767 TSM:ID
58767 TSM:ID:OK
58769 TSM:UPL
58806 !TSF:MSG:SEND,4-4-0-0,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=0,st=NACK:1
60815 TSM:UPL
60852 !TSF:MSG:SEND,4-4-0-0,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=1,st=NACK:1
62861 TSM:UPL
62863 TSF:MSG:SEND,4-4-0-0,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=2,st=OK:1
64872 TSM:UPL
64909 !TSF:MSG:SEND,4-4-0-0,s=255,c=3,t=24,pt=1,l=1,sg=0,ft=0,st=NACK:1
66918 !TSM:UPL:FAIL
66920 TSM:FPAR
66957 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=1,st=OK:
68964 !TSM:FPAR:NO REPLY
68966 TSM:FPAR
69003 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
71012 !TSM:FPAR:NO REPLY
71014 TSM:FPAR
71051 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
73060 !TSM:FPAR:NO REPLY
73062 TSM:FPAR
73099 TSF:MSG:SEND,4-4-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
75108 !TSM:FPAR:FAIL
75110 TSM:FAIL:CNT=4
75112 TSM:FAIL:DIS
75114 TSF:TDI:TSL
``````

Apparently, it sends correctly packets but can't receive any ACK or message from the gateway.
I got this log by connecting a FTDI adapter with only the RX/TX cables. If ever I connect also the GRD and 3.3V of the FTDI, then I get no error message at all (even without the capacitor) and Domoticz receives all updates (and also sends as I use Domoticz to send customized sleep duration to the sensor).

Should I try adding both the 0.1uF to VCC/GRD of arduino and also a 4.7uF to the 3.3/GRD of the NRF24 as suggested in the "Connect the Radio" page ?
Any idea ?
br,
Rico

• @ricorico94 yes add the recommended capacitor.
Also check the gateway log at the same time you check the node log. That will let you know if the gateway isn't hearing the node, or if the node isn't hearing the gateway.

• Thanks for the advice, I'll try that.
For the log on the gateway side : I use a gateway on the raspberry pi itself (as per https://www.mysensors.org/build/raspberry ) of my Domoticz installation. Is there an easy way (like via telnet) to get the logs other than by creating the new line in the config file ? Maybe the 3rd option proposed with "mysgw.pipe" ? (in such case, do I need to reboot whole raspberry after modifying the config file?)

• Thanks to another arduino forum, I found what was wrong.. probably indeed a stability of power due to step-up converter. In that forum, they were explaining that receiving is more sensitive to power noise than sending data and that in such case, it's good to add a 100uF capacitor on 3.3V and GRD of radio module. I tried 100uF and it worked.. I then tried with 47uF and it's still working. (I had tried with 0.47uF and it was not working at all)

In the "Connect Radio" guidelines, of Mysensors, it is stated that a capacitor of 0,47-47uF is improving reliability but that "the exact size usually doesn't matter" which was misleading in my case.
Could I suggest to rephrase that sentence into "the exact size usually doesn't matter, but you can try 47uF if 0.47uF still doesn't work, especially if sending data works well and not receiving data." ?

Edit for Erratum: please read 4.7-47uF instead of 0,47uF-47uF. Tests I had made were with 4.7uF as well, not 0.47uF
br,
Ricorico94

• @ricorico94 great input, thanks! I have updated the page, except that I changed 0.47uF to 4.7uF in your text since the recommendation is 4.7 - 47)

• oups, indeed. I'll edit my post as well to avoid confusion as well. Thank you for your support, I appreciated a lot.
By the way, I could never find how to get the logs in my gateway installed on raspPI. But that's another post.

• Hello together,

I'm just trying to get the voltage measurement to work. But there is something wrong. I built everything as shown above and uploaded the program to the Arduino pro mini. The only thing I changed is the sensing Pin A0 -> A3
In debug mode I see the following (the supply voltage is constant 3.3V):

``````Battery Voltage: 3.12 V
Battery percent: 92 %

Battery Voltage: 2.40 V
Battery percent: 71 %

Battery Voltage: 2.32 V
Battery percent: 69 %

Battery Voltage: 2.31 V
Battery percent: 68 %

Battery Voltage: 2.29 V
Battery percent: 68 %

Battery Voltage: 2.30 V
Battery percent: 68 %

Battery Voltage: 2.33 V
Battery percent: 69 %
``````

What could be the reason? That doesn't make sense to me.

• @maschler You may be picking up noise which will give an unsteady voltage during the ADC sample.
A 0.1uF electrolytic cap between the analogue pin and ground in parallel with the resistor should stabilise it sufficiently.
I use this arrangement with much higher resistances which are known to increase noise, the capacitor maintains a steady voltage sufficient for the ADC sample period.
One thing worth checking with a multimeter is what the actual voltage is on supply and on the pin. The 1.1v bandgap is sometimes not exactly 1.1v, particularly on clones. Once you know the two values you can modify the ratio and you should get reliable and accurate readings.

• The 1.1v reference could be + or - 10%, but a small ceramic cap on near the analog pin should help to stabilize the reading. Also taking 3 measures and then sending the average is a good way of minimizing errors

• I'm looking for a USB rechargeable battery that can deal with very low power drain, so that I can power an Arduino Nano. Most power packs will not work with very small currents - they turn themselves off. So ideally it should not be too clever..

Does anybody have a favourite?

• It would be great to add to this arctle that if you want to be battery powered outdoors with temperature below zero - you have to use lithium batteries (FR6 for AA) (yes, batteries, not li-ion accumulators!) (for example ultimate lithium energizer, also could be found lithium batteries from other vendors), because Alkaline (LR6 for AA) will be frozen and loose their capacity heavily. If i remember it is >50% at -10 C and death at -20 C. Same problem for li-ion accumulators - when liquid is frozen - electrons are stucked...
Also would be great to add some link about battery/accumulator types, advanteges and disadvantages, but i have no links in english, easy-to-read and in one place...

But i have very great link about battery-powering that really should be added here, but in advanced section:
http://www.gammon.com.au/power

• @nekitoss Not sure where you got your information but my Gas Node is on it's second year running on the same two Varta AA alkalines and been down to -20 on more than a few occasions last winter, typically 4 months below -10... Currently the temperature is -3 and headed to -8 overnight, voltage is 2.98, will probably need to replace them in autumn 2019...

• The tap point could be bypassed with a 0.1 uF capacitor

Can someone explain, how exactly I should connect this capacitor? Should it be between A0 and GND? Would be great to see this capacitor in the graphic.

• @benhub That rather depends what you are quoting from, as could not find the original statement.
If it is to do with stabilising voltage from a point on a resistor divider to read it on the analogue pin, the capacitor is from the analogue pin to ground.
It's purpose to dampen oscillations long enough for the ADC to sample the voltage, but usually only where high value resistances are used.

• The quote is from this sample : Measuring and Reporting Battery Level

Use a 1Mâ„¦ (R1) and 470Kâ„¦ (R2) resistor in series, connected to the positive terminal on the battery and ground and then connected the tap point to the A0 input on the CPU.

The tap point could be bypassed with a 0.1 uF capacitor to keep the noise level low, at this otherwise high impedance point.

• @tonbor Yes, the capacitor goes from the analog input to ground.

• @skywatch @tonbor @benhub @zboblamont thanks for your input. I have updated the page. I added the text in bold:

The tap point could be bypassed with a 0.1 uF capacitor (connected in parallel with R2) to keep the noise level low

and updated the image. Please let me know if something is still unclear.

• Perfect!

• If you remove the regulator and power with 2xAA batteries, do you only need the TX and RX pins for the FTDI programmer and if so can you use the RX and TX pins on the left side instead of the top FTDI pin connector? Trying to think how to connect the FTDI programmer without connecting to it's VCC and ground when there is no regulator on the pro mini.

• @macgyver33 you need rx, tx and gnd.

The pins on the left side and the ones on the top work the same way, you can use the ones on the left if you prefer.

• Is exist something "last wish" in MySensors, when battery go below predefined level the device to send last massage to the GW and go sleep forever.
The idea is the controller/application to have information about the device and to be known this device is dead and need battery change.

• @tiana the controller will know the last battery level. Just set the predefined level in your controller?

• Yes but in this case the last massage will be the same like the previous, only the battery level will be below some predefined value. i don't like this. I will think how to solve this.

• @tiana - Of course you can do this in your code.

Just read the battery level and when it gets to the lowest level you decide upon (maybe a little testing needed here) then include the line...

if(battery_level_read < battery_low_level){
send.msg(your last message)
sleep(long time period)
}

You need to define all the things above as normal for variables (floats for the battery reading and levels and UL for the long sleep)....

• @tiana I agree with @mfalkvidd , normally it is the Controller which sends out the warning to change battery, certainly Domoticz has this provision incorporated?
Here the batteries are read at approximate 12 hour intervals, and Domoticz is preset to signal a warning below 1.7v, which is days or even weeks from actually dying. If I'm away or forgetful it will cease updating anyway and flag Red on the display.
Once you have established the consumption curve for your batteries until flat, easy enough to set the warning threshhold before the Node dies...

• @tiana
Create dummy contact sensor on your node and if node sends last message, it will trigger this contact before "die".
So controller knows, that it was last message and node is off.
But better is allow controller do its job, like wrote all others.
I personally check battery level and "no incoming messages in supposed interval" to send alert to my e-mail ( and SMS ).
In this example tank level sensors sends every 10min, so after 3 messages lost, I will be informed.

• Thanks for the ideas, i will modify the code to use LowPower lib and will cut the power to the radio module to increase battery live, when last massage is send the node will never power the radio module, will be only short interrupt and go again to sleep forever. This will give me power usage 20times more than self battery discharge. Which have to give me node uptime around 260days with coin cell battery.

• @tiana
And for what will be that offline node usefull?

• Door/Window/Button

• @tiana
Forever sleeping door sensor with low battery?

"when last massage is send the node will never power the radio module"

Why door sensor, if it never sends message?

• @kimot
At all of the time 328p will be in sleep forever, when button is pressed interrupt is triggered and wake the 328p power ON the radio send info power OFF radio and go sleep forever.
Only when battery level go below critical level. the radio stay OFF and only interrupt and sleep forever.

I am almost ready with the drawings of the hardware, and next week start work on software... you can see the project in the openhardware.io i gonna upload it later tomorrow.

• Hi Guys, I need some help on this guide.
I am running a Nano with radio and Si7021 sensor on 1Mhz to lower the required operating voltage, other than this is unmodified no desoldered led or regulators etc.. I tried running it on 2x 1.5v AA batteries connected to Vin and GND, the LED powers on but nothing else happens. When using 3 AA batteries it does send data, so apparently it needs more than 3v. How can I ensure that the setup is fine with 3V, I bought the 3V AA battery holder but I cannot seem to run it at that currently. Which steps can I take to do so? Help is appreciated.

• @Sebex I run all my nodes with 2xAA rechargable NiMh (or 1 x LifePo4) with Si7021.

1. Use MiniCore bootloader (https://github.com/MCUdude/MiniCore)
2. Set BOD at 1.8V for NiMh
3. Set speed @8Mhz

Enjoy your 1 or 2 years node life at transmit every 5 minutes.

PS Remove the LED and the regulator, of course

PPS I use spare AtMega328p on custom PCB board, but same result with a couple of Nano without regulator.

• @sineverba thanks, I got it working and it's up and running. Still have to desolder the led and remove the regulator, will do that later.
Regarding the BOD, what happens if I disable it? Will it run for longer as it does not shutdown? Or is any voltage below 1.8v bad for the arduino?

A bit off topic maybe, but I was wondering how the 'pros' around here make the sensor small and sturdy for Arduino's with Si7021+ 2xAA battery pack. My DuPont wires seem a bit loose, so I'm wondering whether I should solder them. And perhaps someone 3d printed a case for an Arduino+Batterypack or some sorts.

• @Sebex said in Battery Powered Sensors:

And perhaps someone 3d printed a case for an Arduino+Batterypack or some sorts.

https://www.mysensors.org/build/print might have something you can use. openhardware.io has a few devices with cases.

• @Sebex said in Battery Powered Sensors:

Regarding the BOD, what happens if I disable it? Will it run for longer as it does not shutdown? Or is any voltage below 1.8v bad for the arduino?

1.8V is the minimum voltage according to the atmega328 datasheet. Below that it might work, but it might also do all sorts of strange things. We've seen reports of nodes getting stuck on continuous transmit, blasting radio signals all the time which blocks all other nodes from communicating. So keeping the bod at 1.8V is probably a good idea. 2xAA have almost no power left at 1.8V anyway. See https://www.avrfreaks.net/forum/aa-alkaline-discharge-curve-5ma for some discharge curves.

• @mfalkvidd thanks makes sense, eventually I will switch to NiMh. Had a look at the different cases, gives some good inspiration thanks for pointing in the right direction!

Now that I want to desolder the regulator and LED on the Nano, I just want to verify something, since the video shown is about the mini pro.

(1) Is the circled part in the image below, indeed the regulator on the Nano?
(2) On the battery powered sensor page, step 4 states to cutout the Vout pin. Why does this lower power consumption, and how can I locate this on the Nano?

• @Sebex I have never tried to run a Nano on battery, so I don't know but that looks like a regulator.

The Nano operates at 5V and consumes much more power than a 3.3V Pro Mini.

Yes, the regulator will consume power if it is not disconnected.

• The big chip to the left is also a serial-usb converter which needs to be removed, making it not possible to program from the usb socket. Along with these components there are resistors and other components that might blead current so i dont think its that easy compared to just doing it to a Pro Mini.

• Ok thnx guys, guess I'll be ordering a pro mini very soon!

• @Sebex - i think thats the easiest way, but sometimes its fun to try to create something new - its not impossible, but I would try to reverse engineer the nano (already done - search arduino nano schematic) and there you have to identify all "not essential" components and remove those (ie, making it a big pro-mini) to be able to get the current down as much as possible.

• @Sebex said in Battery Powered Sensors:

A bit off topic maybe, but I was wondering how the 'pros' around here make the sensor small and sturdy for Arduino's with Si7021+ 2xAA battery pack. My DuPont wires seem a bit loose, so I'm wondering whether I should solder them. And perhaps someone 3d printed a case for an Arduino+Batterypack or some sorts.

You may want to try wire wrapping. Itâ€™s faster than soldering, sturdier than DuPont and you can connect multiple wires on same pin. Works wonders for gnd and vcc. Of course if the project is yanked harder, the wire wraps come out.
I made this small video for my home automation group in India. - hence prices for the wire wraps and tool are mentioned in local currency. I leant about this amazing technique from Andreas Spiess
my video
guy with Swiss accent

• @Puneit-Thukral Both DuPont and wirewrap are generally considered as prototyping methods. For final device build and production more secure connections should be implemented.

• @skywatch Agree with every word of yours. Not justifying myself here but wirewraps are deployed all over my house. I pour some hot glue to ensure that they donâ€™t come loose. And then a 3D printed enclosure takes care of the elements.
Also, it helps me to quickly repurpose the hardware.
Itâ€™s just another approach.
In an ideal world - where PCB shipments never arrive from China and locally they are a but expensive , this is my poor manâ€™s alternative. Example photos. The coin cell holder is diy. Used shaving blades and wrapped wires and taped to create a circuit.

• @Puneit-Thukral I understand 'poor mans alternative' soooo well!

Glue on the wirewraps will help keep them in place and mitigate thermal stress to some degree and also stop dust and moisture. But over time the glue will change and shrink/crack and things will start to become strange with that arrangement.

It's hard to beat a good soldered joint in the end, that's why all the commercial kit is done that way.

Nice case BTW. I also am working on 3D printed cases for some nodes. Another 6 weeks of lockdown and I should have started on them!

• @Puneit-Thukral interesting! Seems as a better option than Dupont, I'm gonna look into it.
You mention hot glueing the wires yourself as extra protection. But I imagine you can also put a layer of solder on it right?

• @Sebex yes, of course. I have done that as well. In case I need to repurpose something , removing solder completely away is a tougher job for me than peeling away a layer of glue. Guess, I am just lazy.

• @Puneit-Thukral haha okay I see.

Another question, your case that you use in the video snaps onto the pins perfectly it seems. Did you 3d print that yourself? I'm looking to 3D print a case for my pro mini and some other sensors that snaps in a similar way so that nothing moves around. However I'd rather copy a proven design than figuring out the tolerances myself.

• @Sebex Yes, I 3D printed on my ender 3 and I am using this on nodemcu running ESPhome. But I did not design it. Here is the Thingiverse link to it.
Nodemcu case

I would love to do similar case and a larger case like this to fit other boards. Its rock solid. I do not have skills to make a linear pattern like this. I think I should figure out how to do it.

• @Puneit-Thukral cool, from what I read the pins are the same size as on Arduino's. I'll use this design to create one for myself.

• @Sebex Do share the STL - it will be great and if you use Fusion360, then may I request for the F3D file.. I am semi-skilled when it comes to designing

• @Puneit-Thukral Will do!
After closer inspection the pins of the NodeMCU seem to be a lot bigger in size. However I am struggling to find the correct sizing of Arduino Pro Mini pins (width/thickness). The spacing between pins and length of them are easy to find but I cannot find the thickness at all. Do you have an idea?

• @Sebex Will this help
https://grabcad.com/library/arduino-pro-mini-1
and should we move this conversation to another topic /PM as this is not relevant to this thread.

• @mfalkvidd, on the image I see the following marking in red

VCC ==> N/C

Do you know what the meaning is?
This VCC pin and the other VCC pin at the bottom of the image are connected. I verified with the multimeter.
So, what's the purpose of this remark?

These pins at the right are used to program the pro mini. I had no problems to program after removing the led and the power regulator. The programmer used the VCC to power the pro mini without any problem...

• @evb I believe that the reason is to physically (and electrically) isolate the voltage regulator from the circuit. Then only VCC will work and not RAW.

Essentially the same as removing the led or it's series resistor (only one or the other will do) and the regulator from the board.

• @skywatch, you mean that in normal conditions with the power regulator, we connect the power supply (max 16VDC) to the raw pin and can take 3.3V or 5V, depending on which version, at the pin VCC?
And that now it isn't possible anymore with the regulator removed?

I would propose to change the picture :

• there are 2 VCC pins, so the current picture is confusing
• adapt the drawing and mention to connect the battery (2xAA) 3V directly to VCC pin at the bottom (not the VCC pin in the programming row of contacts!)

@skywatch and @mfalkvidd, what do you think?

• @evb said in Battery Powered Sensors:

@skywatch, you mean that in normal conditions with the power regulator, we connect the power supply (max 16VDC) to the raw pin and can take 3.3V or 5V, depending on which version, at the pin VCC?
And that now it isn't possible anymore with the regulator removed?

Yes, because the regulator will drain batteries faster using raw than connecting an appropriate voltage to VCC....

I would propose to change the picture :

• there are 2 VCC pins, so the current picture is confusing
• adapt the drawing and mention to connect the battery (2xAA) 3V directly to VCC pin at the bottom (not the VCC pin in the programming row of contacts!)

@skywatch and @mfalkvidd, what do you think?

I think it is up to the user to decide what pins they want to connect to and why.

• @evb I don't know what the N/C text means. Presumably N/C stands for Not Connected, but I don't understand what isn't (or shouldn't?) be connected, so I can't say anything about that part unfortunately.

The device can be powered through any of the two Vcc pins. Use the one that is most convenient.

I am not aware of any Arduinos that can handle 16V input on the raw pin. Most clones don't even handle 12V.

If the regulator is removed, the Arduino can no longer be powered through the raw pin.

• @mfalkvidd That's why I propose to adapt the article and image

If even experienced people like you don't know what it means, what should beginners think?
I was confused and did some extra research on schematics, etc on the internet and measurements on my pro mini, afraid to blow up my only TTL to USB programmer after the modification of the pro mini for saving power consumption

The 16V was found on a schematics from the arduino.cc (https://www.arduino.cc/en/uploads/Main/Arduino-Pro-Mini-schematic.pdf). I use typically a 9V power adapter to be safe.

@skywatch You are right that the user finally decides what VCC pins he or she will connect, but we can help him and give a hint : if he uses the right VCC pin to solder his battery wire, he will have a hard time to connect his TTL to USB programmer...

• @evb yes I see your point. But changing things without understanding the background is troublesome, in my experience. Whoever created the original image probably had a good reason to write the N/C part. Therefore, I would prefer if any of the "Ancients" (i.e. people who joined the project before me) could chip in.

• @evb MySensors is a a technical project that involves both hardware, software and firmare. It is not that easy for everyone to follow a single example and then get all that they want.

Think of it as a leanring curve. You already found something that is not the way you want it to be for your use. Many others will agree with that. Some want it a different way.

The main objective is to learn all you can (or need) to get your projects to where you want them. Some out there won't have a single battery node at all, some will be more advanced in battery power conservation than the case in this thread.

I flagged a faulty 'build' example more than 2 years ago, but it is still there and still wrong. But mine works as it should because I studied the data sheets and did it the right way. Change does not come quickly it seems.

You have to put time and a lot of effort into this unless you already work in such an area or have a degree in associated methodolgy.

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