Arduino Mega Power Source

Hey Guys :)

I am giving Arduino a go for the first time, and have very limited knowledge of such electronics aspects, so any help would be greatly appreciated.

The design I have created uses an Arduino Mega, and a ComMotion by Dagu power shield. The design includes (needs to power) 2 ultrasonic sensors (rated at 5V, very small current), 1 servo motor (rated at 4.8 - 6V), 1 stepper motor (requiring 1.2A), and 2 geared motors (rated at 6V, 0.08-2.2A), also 2x mouse sensors (2V each). I have done a fair bit of reading with regards to how I should be powering the device, and am now extremely confused.

The conclusion seems to be to use rechargeable NiMH batteries, which I can source from hobbyking, (http://www.hobbyking.com/hobbyking/store/__342__85__Batteries_Accessories-NiMH_NiZN_Batteries.html), but I am completely unsure as to the voltage power I should be using. Some sites also suggest powering the Arduino + input motors with one power source, and the motor shield with another, and I am not sure if this is the right way to go.

Thanks!

Some sites also suggest powering the Arduino + input motors with one power source

Ignore any site that suggests that. You need appropriate voltage and current for each type of motor (servo, stepper, or geared). You need appropriate voltage and current to power the Arduino (which can power the ping sensors). I have no idea what a "mouse sensor" is. I usually use a rat trap with peanut butter as the bait. But, once it senses a mouse, the mouse becomes useless, so I doubt that is what you mean by a "mouse sensor".

Make sure that all the grounds are connected.

By the way, steppers are not generally powered by batteries, due to the high voltage and current requirements.

Of course a single primary power source can be used, be mains or a battery. But multiple voltage regulators may be required for powering items of different voltage levels, or high power consumption. The Mega includes its own voltage regulators (3.3 and 5V), which can be used in that scheme, for low power (input) sensors (in the mA range).

The 2V mouse sensors look quite exotic, you may need both a specific voltage regulator and level converters from 2V to 5V. But I'd think that these sensors can work with higher voltage, too, please give a link to their data sheet.

Motors or other high power devices require power amplifiers (motor drivers...), available as shields or breakout boards. These boards are connected to their own power supplies or regulators, as required by the load to drive.

And yes, the ground (-) lines of all power supplies and modules must be connected.

Thanks Guys,

So it seems I require a power source for the Arduino board and a power source for the motor shield.

What sort of voltage would I be looking to input into the Arduino board, with the 5V output. Many people seem to think 9V batteries are not suitable for the board, so is 12V the best option? Furthermore, do you have any recommendations in terms of which batteries to use (I have looked into the use of NiMh and Li-Ion, but they are quite expensive.)

@PaulS, the robot I am building has to be independent, as in once the program begins, it runs by itself. What is the best option for powering the steppers then? Thanks

The minimum input voltage for the Mega on-board voltage regulator is 7V, see the datasheet. Alternatively the board can be powered from an external 5V power source.

There exist step-up converters to provide higher voltages from a power source, and step-down regulators for lower output voltages. For best efficiency the battery voltage should be applicable directly to motor driver boards, with no extra losses in voltage converters. Or the motors can be chosen according to the available battery voltage.

The price of battery packs depends on their capacity, size and weight. Compute their energy content from voltage [V] * capacity [mAh]. When you divide that value by the power requirements of all consumers (voltage * current), you get the operation time of your device from a fully loaded battery.