Customer:
We want to power our school Arduino project with a battery charged by a solar panel. The setup uses an Arduino MKR1000 board connected to a laser distance sensor for measuring sea level (tide gauge). The Arduino sends measured data via WiFi several times a day. We’ve added temperature, pressure, and humidity sensors. Do you have components available for solar powering this system?
Original message (Croatian)
želja nam je naš školski Arduino projekt pokretati baterijom koja se puni preko solarnog panela. Projekt se sastoji od Arduinom MKR1000 pločice na koju je priključen laserski mjerač udaljenosti, a s ciljem određivanja razine morske površine (mareograf). Arduino ima zadatak preko WiFi signala odašiljati izmjerene podatke određeni broj puta tijekom dana. Opisani sklop smo nadopunili senzorima temperature, tlaka i vlažnosti zraka.
Originally submitted via email support on 18 January 2022. Migrated to the forum for community visibility.
Soldered Support:
For this setup you’ll need a solar panel - a 12V panel is recommended, since 12V is the open circuit voltage which you won’t achieve under load and without maximum sunlight.
You then need to step down those 12V to 5V for a battery charger. A buck converter works well for this: the LM2596S-based modules or MP1584 3A step-down modules are suitable options. Set the output to 5V (or slightly lower, around 4.7V).
After that, connect a 5V lithium battery charger to the buck converter output.
Finally, connect a lithium battery to the charger, and connect your board to the lithium battery.
We recommend implementing “low power” mode in your code to maximize battery life.
Original message (Croatian)
zanimljiv projekt! Nažalost, u ovom trenutku nemamo savršenu kombinaciju za ono što trebate, ali to ne znači da nemamo rješenje 
Za početak ćete trebati solarni panel, predlažem 12-voltni: https://e-radionica.com/hr/solarni-panel-1-5w-12v.html
Razlog tomu je što je tih 12V napon otvorenog kruga kojega nikada nećete imati kada je spojeno trošilo i osunčanost nije maksimalna.
Nadalje, tih 12V trebate spustiti na 5V koji odgovaraju punjaču za baterije. Ovakav buck converter je dovoljno jednostavno rješenje za to: Step-down modul s LM2596S – Soldered Electronics
Opcija B: https://e-radionica.com/hr/step-down-modul-mp1584-3a.html
Bitno je podesiti izlazni napon na 5V (ili malo niže, recimo 4.7V)
Nakon toga trebate punjač na kojega ćete priključiti 5V s buck convertera: Soldered: Open-Source Electronics, Boards, Sensors & Modules – Soldered Electronics
Konačno, tu se priključuje litijska baterija: https://e-radionica.com/hr/napajanja-i-batt/baterije/punjive.html
I na litijsku bateriju spajate svoju ploču.
Svakako predlažemo da u svoj kod implementirate “low power” način rada kako biste maksimalno štedjeli bateriju.
Customer:
I’ve made a diagram to confirm I understand correctly and would like you to check it. I don’t understand how to connect the lithium battery to the Arduino board since its JST connector is connected to the charger. I also have two more questions: 1. Is a 4000 mAh battery capacity a good choice? 2. Can the cable length be increased for the temperature sensor DS18B20?
Original message (Croatian)
hvala Vam na uputama! Da bih bio siguran da sam dobro razumio, napravio sam skicu koja se nalazi u prilogu pa Vas molim da provjerite. Jedino ne razumijem na koji način se dalje može litijska baterija spojiti s Arduino pločicom obzirom da je njen JST konektor povezan s punjačem pa Vas molim da mi to dodatno obrazložite. Dodatno imam još dva pitanja: 1. Mislite li da je odabir baterije kapaciteta 4000 mAh dobar? 2. Može li se temperaturnom senzoru Vodootporni DS18B20 senzor temperature – Soldered Electronics povećati duljina kabela?
Attachment omitted in migration: Shema spoja - solarno napajanje.png
Soldered Support:
Your circuit diagram is correct! It’s not the most efficient configuration - ideally you’d use an MPPT charger (which we’re developing but don’t have available yet).
- It depends on your board’s power consumption. You need to measure it, then calculate the current efficiency factor from the solar panel, and finally calculate how long a 4000 mAh battery will last.
- Yes, the DS18B20 uses OneWire communication which has cable length limitations, but this can be solved with a smaller pull-up resistor on the communication line. What length cable do you need?
Original message (Croatian)
tako je, shema je točna! 1. Sve ovisi o potrošnji Vaše pločice. Prvo morate nju izmjeriti, a nakon toga izračunati faktor iskoristivosti struje koje dobijete sa solarnog panela i konačno ćete moći izračunati koliko će Vam trajati baterija od 4000mAh. 2. Da, to je OneWire komunikacija koja ima neka ograničenja za duljinu kabela, ali to se riješi s manjim pull-up otpornikom na komunikacijskoj liniji. Koju duljinu kabela trebate?
Customer:
Regarding the temperature sensor, we need about 2 meters of cable length so we can submerge the sensor in the sea. I also need clarification on connecting the MKR1000 board to the battery. Can it be done the way shown in my attached diagram?
Original message (Croatian)
prije svega, hvala Vam na vremenu koje izdvajate da mi date odgovore na pitanja! Što se tiče temperaturnog senzora, trebala bi nam duljina od oko 2 metra tako da senzor možemo uroniti u more. Također, molio bih Vas još odgovor na pitanje o povezivanju MKR1000 pločice s baterijom. Može li se napraviti kako prikazuje priložena skica?
Attachment omitted in migration: Shema spoja - solarno napajanje.png
Soldered Support:
2 meters is not a problem. If a 4.7K pull-up resistor on the DS18B20 communication line doesn’t work, try reducing it to 2k2 or similar.
Your connection diagram is correct. If the shield input voltage is between 3.3V and 4.2V, then it’s fine.
Original message (Croatian)
2m nije nikakav problem. Ako ne bude radilo s 4.7K pull-up otpornikom na komunikacijskoj liniji DS18B20, samo smanjite otpornik na 2k2 ili slično.
Shema spajanja je u redu. Ne znam što je Arduino shield i koji mu je ulazni napon, no ako je između 3.3V i 4.2V, onda je u redu.