How much is the maximum outputs that can be attached to an Arduino ?

Hello, you should be more precise than listing the components. First of all you should see what is the average current supported by the Arduino, that will not be higher than 500 ma supposing you connect it to the USB port. Anyway you can find these specifications on the hardware details board. But you have not specified what Arduino you are using, mini, uno, tre, duemilanove ??? One version operating at 5V or 3.3? Just to speak of the microcontroller side.

Then you should download if not yet have the datasheet of the exact components you plan to have. For sure on the datasheet one of the essential informations reported for every component is the current consumption. Then when you have a clear scenario of the power you need and the power you can provide it is possible to take a decision if the external components should be powered independently or not.

Better if you also notice these things and explain us what do you have in mind. As much things you explain as easy someone can help you in the right way, give good suggestions, advices etc.

Enrico

Hello ,

I am using Arduino Uno

Jose

Please try to follow what I have suggested in my previous post.

Enrico

I am doing a robot for a contest , the main purpose is that it will  help agriculture .

It would be 4 wheel ( sort of truck ) that moves around based on 4 ultrasonic sensors in the front ( 2 in front , 1 in the  right side and 1 in the left )  and it will just sprinkle water and there will be a monitoring 16x2 LCD held by the user to view things like water level in tanks , the temperature of the area surrounding the robot  , etc .

Thx

I am doing a robot for a contest , the main purpose is that it will  help agriculture .

It would be 4 wheel ( sort of truck ) that moves around based on 4 ultrasonic sensors in the front ( 2 in front , 1 in the  right side and 1 in the left )  and it will just sprinkle water and there will be a monitoring 16x2 LCD held by the user to view things like water level in tanks , the temperature of the area surrounding the robot  , etc .

Thx

Ok, Yousif, now you should check the technical details. "ultrasonic sensor" is very generic; check - or search on the net - the technical specifications of these comopnents, that are those that consume current. There are relays that can be managed with a very low power (e.g. the Finder 34.x.x.x series) so untile we don't know exactly the current parameter of every device it is almost impossible to know if the Arduino board can be sufficient or if you need a second power line.

Anyway adding a separate power line is almost simple with Arduino. The ground of the two power lines, the one powering Arduino and one powering the rest of the devices, should be in common while the VCC powering Arduino should be separated but the other VCC that powers the devices. To avoid any problem I suggest a diode (1N4001 maybe sufficient and is almost inexpensive) between the + and - of the external power line. But until there are not more details, we can't go ahead.

Enrico