If you have just started to work with microcontroller boards (Arduino or others) and other electronics, you may have trouble making your setup work. The cause of some problems can be improper powering of the controller board and connected devices.
Sometimes, devices powered from the controller (Arduino) drain too much power for it to handle, sometimes incorrect pins are used for powering. At best, some output devices don't work until the problem is fixed. Worst case - the controller may be permanently damaged.
The controller boards (Arduino and other mega2560 boards) include power inputs (at least one) and outputs for using as power sources for external devices:
The 5V and 3.3V pins located on the board can be used only as source (output) for your peripheral devices if total power consumption does not exeed 500 mA. Don't use them as power inputs!
Vin pin can be use for external source, but be warned that Arduino has no reverse-voltage protection diode on this input. If you will connect it wrong you may permanently damage your board. However, the Mega Pro (mini) controller boards have this protection (these boards have no barell jack)
NOTE: If you cannot power your board through USB (5V) or power jack/Vin (7...9V supply), you can use +5V output pin as INPUT for external +5V power source, but you need to be sure it is a reliable stabilized source of +5V and never exceeds 6V! You can use it only when USB power is disconnected and no power supply is connected to the DC barrel jack.
When your board is powered from USB, you can be sure that the supplied power is exactly 5V and stabilized. USB2 port can supply 500 mA of power (can be less tough!), which is be quite enough to supply the board, the system bus and several low-current devices.
If a DC power source (7-9 V) is connected to the Vin pin or to the barrel jack, the power line from the USB cable is disconnected from the internal 5 V bus (the analog gate is closed by voltage comparator, see the pictures above).
The maximum current for voltage regulator used in Arduino is 1A. But you cannot allow the +5 output to be loaded with such high current. The regulator has a maximum power dissipation rating that cannot be exceeding and it doesn't have the massive heatsink. When you use power supply 12V to down it to 5V it means that the regulator itself should dissipate much of excessive power.
That means that 7V out of 12 are "wasted" and need to be dissipated as thermal power (12 - 5 = 7) and with load of 1A you'll get 7W which is huge power to dissipate as heat.
Even with the load no more than 300 mA the regulator may be overheated without using a heatsink, because it will need to dissipate 2 Watts of power (7 x 0.3).
That's why you need to have a good, stable power source that doesn't have much higher voltage than 5 v you need to get. But there is a minimum limit for input voltage - to get stable output with this type of linear regulator the input voltage should be at least 1.5-2 V above the desired output voltage. So, you need to have at least 6.5 V on input, usually it is 7 - 9 V.
With input of 9V you can load your +5V output with more current (about 500 mA) without overheating and using heatsink. This current is a more than enough to use the +5V output pin as a source for any number of multiplexers connected to SimVim bus and also it can be used to power some output devices - LCDs, PWM controlled coil gauges and other low-current devices (but don't use it for 7-segment displays, multiple LEDs, relays and servo !)
When forming the system bus, you can use the +5V pins located on your controller master board as power line for all multiplexers being connected to the bus. Of course, the bus cable should include at least one common ground wire (GND).
All devices in your system need to be connected to the common GND (the symbol is used as common ground wires for every device pictured on this website).
In general, with SimVim you don't need to use additional power supply connected to your controller board, the power from USB cable is just enough to use +5V output pin for all multiplexers connected to the bus and few other low-current devices. Additional (separate) power supply (5V DC) can be used for powering all other devices that may consume quite much power.
To reproduce all tech solutions presented here and use SimVim Design libraries you should understand all possible risks and carefully learn all aspects of using electric and electronic equipment. Keep in mind the basic rules of connection and powering to prevent controller damage, short circuits, etc.
The usual safety measures to prevent you from burning your electronics/controller include checking if your input/output pins are correctly assigned when you have some devices connected to the master board.
Note that SimVimCockpit configures all controller input and output pins according to the configuration file. As such, if you have some devices connected to your Arduino pins, especially if they are powered output devices, check that these pins are correctly assigned in the "data.cfg" file.
! Leaving the pin unassigned will not cause any problems, but if a pin was assigned for output and you accidentally will connect a switch to this output, you can overload and burn it connecting it to the GND.
This combined diagram was designed to provide you a convenient reference for the proper powering practices for your ArdSimX/SimVimCockpit setup: