Arduino pro mini power consumption, pins' current limit

Projects General Guidance
1

Hi there,

I am starting a project with arduino pro mini that consists of driving 3 servos and and LCD. I'd like to ask if my project is feasible in terms of total current draw and the arduino's consumption.

First, I will need 6 pins for controlling the display plus 3 lines for the servos. The mini has a total output limit for pins cca 145 mA. This will be data only, power will be external. Still, am I running a risk of drawing too much, albeit for the data only?

Second. This might seem especially dumb but I've never actually run arduino off a computer whereas now I want to use it as a stand-alone gadget. The project requires basic but continuous operation of the program (24/7), waiting for buttons being pushed, etc, then occasionally moving the servos for example. Is that okay for the chip itself and does anyone know what the board's consumption will be at the time it is just running the program but not performing any actions (moving the servos, etc.)? I would like to find out this way how long this can go on a battery.

Thanks a lot,
Mike

2

It's much easier to measure the current draw than it is to calculate the current draw.

3

I would like to find out this way how long this can go on a battery.

That would depend on the size of the battery, wouldn't it?

4

Well, of course. But I have no idea how much current an arduino draws.

5

MikeMino:
Well, of course. But I have no idea how much current an arduino draws.

The actual chip doesn't use much at all, about as much as a couple of LEDs. The stuff connected to it is much more important. Turn everything on 100% then get a multimeter and measure it.

Servos can draw a lot of current, that's why you're supposed to use external drivers for motors - so you don't overload the Arduinos pins. The actual amount depends on the load they're trying to move though (how much torque they're producing). For light loads it isn't much. Again, you'll have to measure it.

6

Thank you. If you are pretty sure about the Arduino's consumption being equal to a couple of LEDs, i.e. tens of mAmps, that's precise enough for me.

Do you know as well what's the power consumption of an idle servo? I plan to drive them separately but I'd like to know how much current they will draw from the batteries when stationary.

Thanks a lot,
Mike

7

MikeMino:
Thank you. If you are pretty sure about the Arduino's consumption being equal to a couple of LEDs, i.e. tens of mAmps, that's precise enough for me.

Do you know as well what's the power consumption of an idle servo? I plan to drive them separately but I'd like to know how much current they will draw from the batteries when stationary.

Should be very small. The motor itself won't be drawing anything, only the motor's control circuit.