[engolling]

Hello Guys,

I found a view minutes to make the documentation for my WeatherDuino UPS ready.
It is working with RX and TX modules which are normally powered by mains to keep them working even if there is a power outage.
It is supposed to be plugged in directly in between the powerline of the WeatherDuino system.

The system is cheap and easy to build and consists of the following parts:

• SBX 3030 Schotky diode
  
• TP 5100 Lithium-Ion Battery Charger board
  
• FDC 2s-2 protection board alternative a HX-2S-JH20 board will fit
  
• 2s 18650 cell holder
  
• 2 18650 Lithium-ion cells (not LiFePo) - I recommend quality products from the known brand
  
• NC bimetall disc switch 45°C
  
• XL 6009 DCDC converter - I recommend the one with voltmeter
  • If you use the small footprint converter without voltmeter you have to bring a 1000µF capacitor at the input of the XL6009 in place. Use the holes of the big footprint XL6009 for this.
    
• fuse holder 5x20mm for THT mounting
  

Here you can find the schematic:


And here an easy scheme how to interconnect the system:
 

Additional Information:
The diode should prevent that the battery charges itself and also a backward current to the supply or whatever comes there. It also should have a very small voltage drop so that's why I chose such a big thing. You might use another one - but at least you will need it.

I would warmly recommend to buy high quality original cells from a European or American supplier. They will cost around 5 EUR oder USD each, but it is worth it because of performance and safety reasons.

The bimetal temperature switch should be placed in the notch between both 18650 cells so it gets in touch with both cells.

The protection board only has to be connected properly than it will work out of the box.

On the TP5100 module you will have to connect the set pads soldering it together to enable 8.4V charging, otherwise it will only charge up to 4.2V.

The XL 6009 DCDC converter has to be adjusted to the correct voltage. It should be about 0.2 or 0.3V lower than the voltage you can measure at the WeatherDuino if it is not connected. Be sure to adjust it always before connecting because a too high voltage set here might damage the WeatherDunio!
It is also recommend to put a glue dot on the potentiometer after the voltage is set to prevent it from moving again.

Last but not least, if the 2s1p connection does not have enough energy you could switch two other cells in parallel so you get a 2s2p circuit. But be sure, that the circuit is cellwise switched in parallel otherwithe the protection board can not work properly.

And now you can use your UPS with your WeatherDuino, you can hotplug the power supply and it will keep running without interruption for serveral hours.

 

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This is how the system installed on the PCB looks like:



Attached you can also find the schematics. Please be aware that you can see both options which can used as protection board and both options for the voltage regulator.
You need to install only one protection board and one voltage regulator.
 

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Best regards,
engolling

[hornychz]

[werk_ag]

Interesting work!

What you think about design a pcp where we could integrate those modules, making a compact unit?

Definitely I would like to build one or two of these things. My main weather station receiver (as the PC running Cumulus) is powered via an 220V UPS, but this small UPS will be very usefull for my other test units.

The XL 6009 DCDC converter has to be adjusted to the correct voltage. It should be about 0.2 or 0.3V lower than the voltage you can measure at the WeatherDuino if it is not connected. Be sure to adjust it always before connecting because a too high voltage set here might damage the WeatherDunio!
It is also recommend to put a glue dot on the potentiometer after the voltage is set to prevent it from moving again.

The use of DCDC converter with a voltmeter included may help to quickly check the output voltage before connecting the UPS to the load (WeatherDuino is this case)

[engolling]

What you think about design a pcb where we could integrate those modules, making a compact unit?

I already thought about this and I like the idea - do you think the battery holder should also be integrated on the pcb or not? In my opinion it nearly gets to big then.

Another thing is, that the 3A protection boards I found never have holes to mount it on a PCB - does anyone has an idea how to mount them elegantly?

(I thought for a few seconds about designing it from scratch but all the smd soldering and testing I think it's not worth it)

[werk_ag]

I already thought about this and I like the idea - do you think the battery holder should also be integrated on the pcb or not? In my opinion it nearly gets to big then.

I thought about that too. Having the battery holder integrated on the PCB, will produce a more compact and possibly easy to assemble unit, but it have the disadvantage of largely increasy the cost of the pcb, due to the extra size. So, perhaps the better is option for having a separated battery holder.

Another thing is, that the 3A protection boards I found never have holes to mount it on a PCB - does anyone has an idea how to mount them elegantly?

Sorry for asking, it should be obvious, but what is on this module? It seems a bare pcb, surely isn't.
Do you have any link for it?

(I thought for a few seconds about designing it from scratch but all the smd soldering and testing I think it's not worth it)

I fully agree. Whenever there are available already made modules for anything, its always cheaper using them, than designing from scratch.
On this, even there are interesting things: At least on eBay, a PI RTC module, it cheaper than the RTC chip included on the PI module.

[engolling]

Hi Werk,

concerning the Battery and PCB - it would work to mount the batterys on one side of the pcb and the electronics on the other one.

The protection PCB I'm talking about looks like this:
https://www.aliexpress.com/item/32822717860.html

No drillholes and no surface mount possible because of the ICs on the other side and I could not find a supplier for a similar one with better layout.
All solutions I can imagine at the moment are not "nice" and are containig some flying wires

Regards,
engolling

[engolling]

Update - I ordered some stuff THT mounted 18650 holder and the dcdc converter with voltmeter. Moreover I will use a "bigger" protection board with holes I can mount via pins and I will add another fuse.
So when the stuff arrives (it may take some time from china)  i will take out my ruler and then design a compact pcb - so stay tuned

@Werk You got me hooked on this project even I have no time either    just like you 

[werk_ag]

I say it many times! The WeatherDuino it's a dangerous thing, it causes addition very quickly. When we realize it, is too late.
I'm afraid that there is no solution for you anymore.

This small UPS is an addition which I want to have. No rush, despite the addiction, there is our own jobs and other life affairs.

[engolling]

Faster than I thought it might be possible - the first draft of the PCB and the schematics in attachment.
I would be glad if you could comment if something it wrong, strange, not good or whatever.

Next steps:

1. Update the right pin positions of the TP5100 - I did not have one here
   
2. Add the layout of the XL6009 without voltage display
   
3. Print it on paper to check if holes are fitting
   
4. Order PCBs
   

Regards,
engolling

[engolling]

Added the possibility to use the PCB with the XL6009 without voltmeter and the FDC-2S protection board (I did not try how soldering will work) as well as the possibility to install a buck converter for 5V output.

Thus it should be ready for manufacturing  . Besides some of you have concerns...

Regards,
engolling

PS. I know I squeezed the other protection board in