I can't seem to find the answer to this anywhere online.
I want to power a good about of stuff and was hoping to do it through the Mega. I have dozens of LEDs, a sound sheild, some servos, LCD 4x20, and a bunch of other stuff.
BUT
I can't find a definitive answer on how much power the board can supply.
I see that each digital pin can offer 40-50 mA, yay. What about 'VIN'? I keep reading about it -- is it just a straight draw from the barrel plug to that pin? Can I use VIN to supply power to all of my stuff as long as the wall-plug-transformer can handle it? ... or will I kill my Mega?
And how much can I power with the +5v and +3.3v? Can I supply power through all of these simultaneously?
Here is what I've found online in the documentation:
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VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.
5V. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.
3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum current draw is 50 mA.
GND. Ground pins.
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okay so 3.3 has a maximum draw of 50 mA.
Nothing is said about the +5v maximum draw.
Nothing is said about the VIN maximum draw (my board is powered by the 9v barrel plug).
See my frustration? I'd rather not kill my board.
Heeelp me
On page 367 of the data sheet is says:
Operating Temperature.................................. -55°C to +125°C *NOTICE:
Storage Temperature ..................................... -65°C to +150°C
Voltage on any Pin except RESET
with respect to Ground ................................-0.5V to VCC+0.5V
Voltage on RESET with respect to Ground......-0.5V to +13.0V
Maximum Operating Voltage ............................................ 6.0V
DC Current per I/O Pin ............................................... 40.0 mA
DC Current VCC and GND Pins................................ 200.0 mA
This means that the total delivered by all pins must be less than 200mA.
Vin: current is only limited by the power source, but in practice also limited by the power dissipation of a diode (that prevents reverse voltage in case the power source is backwards). The schematic does not list what diode that is so I would guess <1A is safe.
+5V: When coming from an external supply, limited by this same diode and also by the current and power dissipation of the MC33269D or MC33269ST regulators. These are listed as being limited to 800mA but practically they will be limited by heat.
The heat (power dissipation) depends on the input voltage according to P=(Vin-5)*I where Vin is the input voltage, I is how much current you are drawing from +5V, and P is the power dissipation. I would estimate that P should not exceed about 600mW to keep the regulator's temperature in its safe range (ballpark estimate). Soooo....if you believe this number then you have to trade off Vin for I. The higher the Vin, the lower the I you can draw from +5V.
Now, when +5V comes from USB, there is a 500mA resettable fuse, which means you can draw anywhere from 500mA to 1A before it trips because these things are not precise devices. The USB specification, however, limits current to 500mA so you should not expect to draw any more than 500mA. Note that this includes powering the ATmega itself (30-40mA I'm guessing) so leave some headroom.
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The Rugged Motor Driver: two H-bridges, more power than an L298, fully protected
3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum current draw is 50 mA.
but the 2560 mega doesn't HAVE an FTDI chip. The 1280 mega used that to do USB / serial conversion. The 2560 board replaced it with an Atmel ATMEGA8U2 and does 3.3 v power regulation with a LP2985-330. The LP2985 seems to be capable of 150 mA; just how much might be available for a lightweight project is beyond my amateurise (the opposite of expertise).
A note on sourcing power. I use a 5v adapter usually used for a DLink or other router - this provides 2 to 3 amps worth of nice 5v power for running LEDs and the like. Be sure to use a tester to assure the power level, sometimes they are 4.9 to 5.2 .. all of which have worked fine for running RGB leds .. even ones with chips included.
There are also higher end power supplies that provide much more power if needed as well.
Assure you connect the ground from the external power to the arduino ground or it won't work right -
