Is it ok to use 12v 15Ah lead acid battery in arduino
Because I want to make a project, solar based automatic waste segregator
The sensors requires 6v minimum (inductive and capacitive proximity sensor)
And I would like to add some charging ports for my project
Hi there, and welcome!
This is a question that can be answered with 'Yes' and 'It depends'.
Yes - It can be powered by 12 V.
It depends - on how long 15 Ah will be able to power the Arduino + the other things you mentioned before being recharged.
Can you provide more details about the setup, what gear do you plan to use (beside a 12 V 15 Ah battery) ? The PV arrangement, charger, sensors etc. I assume you wanna interface those sensors with the Arduino, if they work at 6 V some level conversion is needed or the Arduino won't be happy.
Solar charging means your solar panel will sometimes need to supply all the power necessary to run all the motors and servos and solenoids of your system, and charge the battery at the same time. Have you computed the power requirements for your project? If your system also has to operate with snow on the solar panel, the 15Ah battery will not run for very long.
Depends on the Arduino. There are many different models, some can use 12V others cannot.
Know that at top charge those car standard batteries will reach up over 13 volt, nearly 14. That is out of spec for several controllers as I've got it.
Agree, better get an external DC/DC solution.
Why?
For one thing.
So are you proposing a universal solution that will work with any and all Arduinos?
Isn't that going way overboard?
Wouldn't that be lovely. Then world peace. 
A step down converter will handle it well.
Then It's unclear what you mean, an R4 would not require an external DC/DC with 12V.
I didn't know that. What's the max voltage it can take?
Standard charging for car batteries is 14.8V. Some chargers incorporate a ‘repair’ mode giving 15.5V or more.
You might be using a closed cell battery, in which case you shouldn’t charge over 13.8V.
The official numbers from Arduino documents:
UNO R3 / Mega 2560 / Nano (classic): 12V
UNO R2 WiFi: 20V
Nano 33 BLE / RP2040 / ESP32 / Every / Matter: 21V
UNO R4: 24V
Nano IoT: 5V
For the set up I'll be using Arduino uno R3
for the sensors:
Inductive proximity sensor
Capacitive proximity sensor
2x E18-D80NK IR sensors
3x Ultrasonic sensor (trash level)
2x Servo motor SG90
Charging port
Power supply setup:
Solar Panel 200W
PWM solar charge controller
12v 15Ah lead acid battery
Hi, @jerus
Welcome to the forum.
It would be better if you Googled your battery make and model and got the manufacturers specs.
They should tell you, charge rates, floating and boost voltage parameters.
Tom.... 
I think that you'll find you need more than 200 W to support all that equipment. It's just during the peak of the day the panel produce 200 W (or close to). But you'll figure it out pretty soon. For your Arduino a voltage regulator is needed, but a buck converter is better since you're on a limited power budget.
Then you must figure out how to interface those 6 V sensors with the Arduinos 5 V.
The battery will need 12 x 15 =180Wh of energy to fully charge.
If you have sunlight for just 1 hour, then your solar panel will generate 200Wh of energy.
So you have more than enough solar power to charge the battery, with some extra for running the system.
First hurdle: E18-D80NK IR sensors:
Some sites suggest to feed it from VIN of your UNO R3.
Others sites suggest to feed it from the 5V pin of your UNO R3.
Both are wrong, but they agree on max supply of 5V.
Assuming you feed your board from 12V, feeding from VIN may damage the sensors, feeding only one from the 5V pin the sensor will push the on board 5V regulator to it’s limit.
Using this sensor makes a DC/DC converter necessary, best use a switching one.
One site advised to connect the output to an analog input. This is not logical, it’s a digital output.
Info from different sites combined: output is a NPN output with internal pull up resistor, so pinMode PULLUP is probably not necessary.
If the sensor allows for a higher supply voltage (see nameplate) it’s pull up may damage your input pin. Even at a separate supply of 5V it may damage your input pin when the supply to your board is switched off.
Considerations like this are necessary for each component.
In this case protection can be simple:
