New WX project launched
Moderators: grovkillen, Stuntteam, TD-er
New WX project launched
Hi,
i would like share some pic of my last project. Its a WX station with solar power and LORA modem...
Custom made PCB for HTU-21DF, radiation shield
I can provide gerber or stl files for production.
Many thanks to TD-er for the help in solving the problem... !
i would like share some pic of my last project. Its a WX station with solar power and LORA modem...
Custom made PCB for HTU-21DF, radiation shield
I can provide gerber or stl files for production.
Many thanks to TD-er for the help in solving the problem... !
Re: New WX project launched
Looking good
Glad you finally got it all working.
At what altitude is the station mounted?
Looks quite high on the pictures
Glad you finally got it all working.
At what altitude is the station mounted?
Looks quite high on the pictures
Re: New WX project launched
Wow, it looks really good. Nice project!
Re: New WX project launched
Nice!
- Thomas
- Thomas
Re: New WX project launched
Looks very solid. What battery configuration are you using?
Re: New WX project launched
4P? As I cannot see a charger circuit, how do you charge them? And this DC/DC is for 3.3 or 5V?
Re: New WX project launched
So you are using the buck converter as a charger? I am not sure it's a good idea, LiPo batteries require Constant current/Constant voltage charging mode to be properly charged. Without that you may have them undercharged (low efficiency) or overcharged (risk of fire). If you plan to optimize this setup, I would say one 3000 mAh cell would be more than sufficient for your panel size, 4x looks like an overkill
Re: New WX project launched
The battery cells are Li Ion, I have been using this solution with a simple DC-DC for several years and there is no problem with it, maximum current from solar cell is 0,6A, but Yes, I will modify for better efficiency, I will use CN3791 designed for LiIon charging. One battery cell of 3000 is not enough, because if it is cloudy for several days, the weather station would not be able to function.chemmex wrote: ↑08 Nov 2022, 22:37So you are using the buck converter as a charger? I am not sure it's a good idea, LiPo batteries require Constant current/Constant voltage charging mode to be properly charged. Without that you may have them undercharged (low efficiency) or overcharged (risk of fire). If you plan to optimize this setup, I would say one 3000 mAh cell would be more than sufficient for your panel size, 4x looks like an overkill
Re: New WX project launched
CN3791 is a good choice, but to make MPPT work, it requires that panel's capability should match the charging current. From my experience, when your charging current is set for example to 2A, but your panel can provide only 0.3A @17V, then the circuit will collapse. It will work as if there's a diode between the panel and battery, dropping the voltage to 4V, very far from MPP. So to make it work as expected, you should either choose larger panel or decrease the charging current by using higher shunt resistance. But, if you decrease the charging current, there's no guarantee that your ~10Ah battery will ever be fully charged.
I would suggest you to look at sleeping mode. There are at least two reasons for that: first, there's no need to keep the node powered between LoRa transmissions, especially if you are using TTN. Second, you can optimize the battery and, consequently, the size of the panel needed to charge it.
For example, I have a setup with PMS7003 and BME280 sensors which works on 3W solar panel and 1500 mAh LiFePo4 battery all year round. Typical measurement and reporting interval is 5minutes, but it can be adjusted depending on the battery charge state and time of the day.
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