💬 Easy/Newbie PCB for MySensors

[popunonkok]

Iv just orderd Rev8.

I have a primary question, might have a couple more later on.
In the info about the board it says:

"BAT: Short this if you are using batteries as power supply. It will activate booster circuit and feed the radio directly from the batteries and not voltage regulator"

It says about the same on the image of the board.

My question is. Why would I want to powewr the radio directly from battery and not from the Booster? Wouldent that make the radio not to function like it sould when the voltage dropps?

[sundberg84]

@popunonkok - if you search the forum and this thread about noice in the boosters you will find a big search result. The boosters is, to be honest, pretty bad. They generate alot of noice which interfere with the radio which is pretty sensitive. By "learning by doing" we have figured out that if you are using a booster the best way is to provice power to the radio directly from the batteries to avoid the noice... the radio will pretty much fail if you dont.

The radio can handle down to 1.9 v so this will be your minimum voltage for the circiut.

[popunonkok]

Hmmm... Ok...

I had only read that the boosters helpt to drain the battery completely, had missed that they "messed" with the radio.

It will be really interesting to see what kind of battery life I can get out of 2 or 4 AA batteries on different types of nodes.

When I look at the Specs for the Pro Mini board the supply voltage is 3.35 - 12v.
I guess that means that without a Booster 2 AA batteries wont be able to run the Pro mini for a long time at all.

[sundberg84]

@popunonkok - you are correct, they are good for they "suck all the juice" out of the batteries. Without modifications the Pro Mini 3.3v have a lowerst voltage of 2.8V (called Brown out detection) Because of that when you use 2xAA you need the booster to keep a stable 3.3v and most of the booster can convert everyhing down to 0.9v back to 3.3v. The radio can handle down to 1.9v and that will be your lowerst point.

I have nodes reading temp and humidity with a dht22 every 15min, running this setup and they last around 1 year each.
You need to search the forum and https://www.mysensors.org/build/battery for power saving with battery. The most common first step is to remove the voltage regulator and the led. Then you sleep the node when it isnt active.

On this image you see the led removed (red arrow). I think its easier to remove the resistor (black circle, marked 102) but its the same result. Voltage regulater (red circle) is removed as well. Note that many sites say cut the trace but its much easier to desolder them.

Using the internal voltage regulator (3.35 - 12v) will kill the node in weeks/days if you run them on 2-4xAA because of the high current drain. My aim building a newbie/easy PCB is a sleepcurrent of 0,1mA or 100uA.

[chrlyra]

hi there,

Thanks for the easypcb! I'm trying to build a small solar powered weather station (like these: https://forum.mysensors.org/topic/841/solar-powered-mini-weather-station), but just found that the battery that came with the solar panel only provides 1.2v. The booster works ok and I can power the arduino, but it's no enough for the radio :-(. Since powering the radio from the booster is not a option, I'm at a dead end. Or there's a way to still using this battery/solar panel?

[sundberg84]

@chrlyra - you need 1.9V minimum for the radio. There are more advanced boosters you could try which probably is better and less noice... but this PCB was not designed for that purpose so sorry, I cant help you.

[gohan]

@chrlyra
There is another project called solar harvester that uses a supercap to store energy

[dbemowsk]

So a question I have always wondered about the voltage regulator is do you really need to desolder it if you connect your incoming power to the 3.3v pin and not the RAW pin? I would have thought the regulator would only drain power if it was converting the RAW power down to 3.3v.

[sundberg84]

@dbemowsk - your logic sounds right, but i think it will draw power anyway... only way to figure out is to measure or google :)

[popunonkok]

I managed to change my PCB order, I saw that one of the updates to rev9 was the ability to use Pin 2 as GPIO instead of going to the Radio where it is unused. So now I have a order for Rev9 instead.

I will try to desolder the led or resistor and the voltageregulator.

Thanks for sharing your design.

[sundberg84]

@popunonkok Good luck - let me know if there is any other questions.

[Nca78]

@dbemowsk in fact current is leaking through the regulator when its input is floating, you can check the "reverse leakage current" value on the data sheet of the linear regulator used on your promini boards then decide if you can accept it or not, depending on your circuit.

[ileneken3]

Hi -

I wanted to know if this config is OK:

Attach a LIPO battery to PWR and GND.
Cut off the right side of the board.
Use a 3.3V pro mini.
Add a regulator (like a MCP1700) and necessary caps. (Spec says 1uF).

The idea is that the board and sensors get 3.2V - 4.1 V (which should be OK).
The radio gets 3.3V.

Thanks!

[sundberg84]

@ileneken3 - sounds right, you should short the jumper REG which will feed everything the LIPO voltage. If this is higher than 3.3v I dont know what will happen but adding the voltage regulator for the radio will make sure that one is ok. I dont know about the pro mini, it it can handle up to 4.1v but I guess you will find out.

[gohan]

I'm curious too if will handle the 4 volts or not😀

[Nca78]

No problem with the promini. Limit is from atmega and it's 5.5V I think (at least 5V anyway :) )
You will just have HIGH level voltage at battery voltage at the outputs instead of 3.3V

[gohan]

So technically you can power a 3.3V pro mini with a LiPo battery, you only need a regulator for radio, correct? Can you still make reliable battery voltage measurement? I Have a NRF24 adapter with a AMS1117 onboard, will that still work or does it need 5v?

[Nca78]

@gohan said in 💬 Easy/Newbie PCB for MySensors:

So technically you can power a 3.3V pro mini with a LiPo battery, you only need a regulator for radio, correct?

Correct.

Can you still make reliable battery voltage measurement?

Yes, check here :
https://forum.mysensors.org/topic/186/new-library-to-read-arduino-vcc-supply-level-without-resistors-for-battery-powered-sensor-nodes-that-do-not-use-a-voltage-regulator-but-connect-directly-to-the-batteries

I Have a NRF24 adapter with a AMS1117 onboard, will that still work or does it need 5v?

From the datasheet typical dropout voltage is 1.1V and it can be up to 1.3V.
So to get 3.3V at the output you need at least 3.3 + 1.1 = 4.4V. It won't work with your battery, you need to use another voltage regulator with a much lower dropout voltage.

[ileneken3]

@Nca78

At least according to the specs, mcp1700 will do the trick (both in terms of drop out voltage and low power consumption for battery usage). I will try it.

[gohan]

I have seen these boost/buck converters https://www.aliexpress.com/store/product/5pcs-mini-1-8V-3V-3-7V-5V-to-3-3V-Boost-Buck-Low-Noise-Regulated/1525466_32365767349.html

https://www.aliexpress.com/store/product/2PCS-Auto-Buck-Boost-DC-DC-Converter-Voltage-regulator-module-0-9-6V-to-3-3V/1525466_32757272432.html

Would they make any sense to use with LiPo batteries or other solar power source to power a node? Or would they waste too much energy?