[engolling]

Thank your for your Feedback.
The actual idea is to supply the device with the voltage rail comming from the power supply and the batteries only provide power if the supply fails.
This works fine now in a range of 9-12V but not at 5V since the carger is not able to boost the voltage. Supply must always be higher than battery voltage.

In changing the battery config from serial to parallel connection it would work with the same design by setting a solder junper.

But also here the input voltage must be the device voltage.
By adding another dcdc converter we could archive the desired functionality of Werk but we also rise the losses.

Current can be provided up to 3A but be sure to user proper connectors to stack the modules

Regards, stefan

[werk_ag]

Hi Stefan,

Thank your for your Feedback.
The actual idea is to supply the device with the voltage rail comming from the power supply and the batteries only provide power if the supply fails.
This works fine now in a range of 9-12V but not at 5V since the carger is not able to boost the voltage. Supply must always be higher than battery voltage.

I don't see any problem in keeping the input voltage at a minimum of 9V, indeed I even think it is preferable. 9V or 12V DC/AC wall adapters are easier to find than a 5V AC/DC adapters and tend to be cheaper for 2 or 3 Amps. What you think?

In this case, could you keep the actual design with the batteries in series?
Can we just adjust the current DC/DC convert for the desired output voltage (From 5V up a voltage near the Input Voltage). If yes, that is simple great. It will work with any WeatherDuino device, from receivers to the transmitters, or any 5V devices like the WiFi WD units, or even any other future WeatherDuino device.

[engolling]

I would like to have support down to 5V because with phone chargers and USB-C chargers this is and will be very common. And you also will have some devices.

Since the actual solution does not satisfy myself fully I will look for some solutions allowing 5-15VDC at the input and 5-12VDC at the output... indipendent from the input.
I will also add some more diodes and maybe a resetable fuse to make it failsafe agaist wrong polarity of in- and output.

So stay tuned for the next version.

Nevertheless this one can be used for the Pro2. If someone likes a PCB you can buy some of the left prototypes for 3EUR + 3,70 EUR shipping.

[laulau]

....

Nevertheless this one can be used for the Pro2. If someone likes a PCB you can buy some of the left prototypes for 3EUR + 3,70 EUR shipping.

Hi,
Im interested. PM please to define how I buy it.

[werk_ag]

A solution would be to design the PCB that the second DC/DC can be bridged so the DC/DC boosting the battery voltage can be adjusted to the voltage of the main rail - so those who already have the correct power supply for the device do not need another conversion and those ones who want it for which reason ever can install it.
I think this would be the best trade-off.

I'm looking foreward to your feedback .

Fully agree.

[engolling]

Since there will be a view pieces of the first version in the field soon a brief summary from my side:

The system will output the same voltage as you have on the input side minus the foreward voltage of the used diode. That's why I recommend a oversized Schottky diode.
Be aware that you will have to adjust the DC/DC converter after the battery to a voltage slightly below the voltage at the output, otherwise there will be a steady current over the charging borad.

I also recommend to solder the boards directly to the connection board with 1mm wires or similar and put a spacer below. Pin headers also work but lead to instability and voltage losses due to bad contact resistance.

The following parts can be used:
 

• SBX 3030 Schottky diode or similar
  
• TP 5100 Lithium-Ion Battery Charger board
  
• FDC 2s-2 protection board alternative a HX-2S-JH20 board will fit
  
• 2s 18650 cell holder THT version with pins
  
• 2 18650 Lithium-ion cells (not LiFePo)
  
• NC bimetall disc switch 45°C
  
• XL 6009 DCDC converter (with voltmeter and without voltmeter)
  
• fuse holder 5x20mm for THT mounting
  

If you have questions if a specific device will fit, don't hesitate to write me.

[werk_ag]

First items to build my two units arrived... ordered them from a German seller.



@Engolling
Regarding the Schottky diodes, I'm planning to use these ones:

SB5100 - http://www.smc-diodes.com/propdf/SB5100%...0REV.A.pdf

They are only 5A, do you see any major problem?

[engolling]

Concerning the diode you will have a voltage drop of about 0.7 to 0.8 V so the device will see about 8V input voltage. I do not have the schematics in my mind at the moment but the 5V linear regulator should be fine with it.

[Derek]

Hello,
PSU Feed back
Just to say that I have completed engolling's UPS and it is working great.
I used one of his prototype boards.
I switched it on for 24 hours, then unplugged the power supply.
I then left it for 3 hours and it powered the Weatherduino with no problems.
It is now back on the mains supply.
Many Thanks to Engolling for this project.

Regards Derek

[hornychz]

Stefan,

I think it is good time to prepare an article to our WiKi!