New WX project launched

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mra2ko
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New WX project launched

#1 Post by mra2ko » 07 Nov 2022, 22:00

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... !
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TD-er
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Re: New WX project launched

#2 Post by TD-er » 07 Nov 2022, 22:08

Looking good :)
Glad you finally got it all working.

At what altitude is the station mounted?
Looks quite high on the pictures

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chromo23
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Re: New WX project launched

#3 Post by chromo23 » 07 Nov 2022, 22:11

Wow, it looks really good. Nice project!

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Ath
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Re: New WX project launched

#4 Post by Ath » 07 Nov 2022, 22:16

Impressive :!:
/Ton (PayPal.me)

mra2ko
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Re: New WX project launched

#5 Post by mra2ko » 07 Nov 2022, 22:20

This WX is around 550asl, I must make some modification on PCB and next WX will be in 640asl and 9km to lora AP, home made 3EL Yagi is tuned :)
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TD-er wrote: 07 Nov 2022, 22:08 Looking good :)
Glad you finally got it all working.

At what altitude is the station mounted?
Looks quite high on the pictures

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ThomasB
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Re: New WX project launched

#6 Post by ThomasB » 07 Nov 2022, 23:20

Nice!

- Thomas

chemmex
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Re: New WX project launched

#7 Post by chemmex » 08 Nov 2022, 08:05

Looks very solid. What battery configuration are you using?

mra2ko
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Re: New WX project launched

#8 Post by mra2ko » 08 Nov 2022, 10:10

chemmex wrote: 08 Nov 2022, 08:05 Looks very solid. What battery configuration are you using?
Now is inside 4x LIION 3000mAh, is easy to upgrade for 8x. We will see in winter, maybee will be the upgrade need it, or enable deep-sleep...

chemmex
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Re: New WX project launched

#9 Post by chemmex » 08 Nov 2022, 10:24

4P? As I cannot see a charger circuit, how do you charge them? And this DC/DC is for 3.3 or 5V?

mra2ko
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Re: New WX project launched

#10 Post by mra2ko » 08 Nov 2022, 21:51

chemmex wrote: 08 Nov 2022, 10:24 4P? As I cannot see a charger circuit, how do you charge them? And this DC/DC is for 3.3 or 5V?
4x cell parallel. Is a SOLAR - INA219 (for info about solar current)- DC/DC - BATERRY + MCU, all devices is on 3,3V, just FAN is direct from baterry

chemmex
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Re: New WX project launched

#11 Post by chemmex » 08 Nov 2022, 22:37

mra2ko wrote: 08 Nov 2022, 21:51 4x cell parallel. Is a SOLAR - INA219 (for info about solar current)- DC/DC - BATERRY + MCU, all devices is on 3,3V, just FAN is direct from baterry
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

mra2ko
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Re: New WX project launched

#12 Post by mra2ko » 09 Nov 2022, 10:55

chemmex wrote: 08 Nov 2022, 22:37
mra2ko wrote: 08 Nov 2022, 21:51 4x cell parallel. Is a SOLAR - INA219 (for info about solar current)- DC/DC - BATERRY + MCU, all devices is on 3,3V, just FAN is direct from baterry
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
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
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Re: New WX project launched

#13 Post by chemmex » 10 Nov 2022, 16:31

mra2ko wrote: 09 Nov 2022, 10:55 I will use CN3791 designed for LiIon charging
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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