But I have started to question my thinking about Power Distribution.
I think I drew 5 Volt input on all 5 Volts. This must be wrong?
This is how I think:
All ground must be connected.
I should connect 7-12 Volts on the VIN pin
What do I do with the rest of the Power Pins?
If I use Pokeys, it wants 3.3V for Potentiometers, while Arduino wants 5 V. I think this should be solved by +Analog being connected in parallel on the shield to either 3.3V on pokeys or 5 volts on Arduino. Then the question is which 5 V should I use? External or internal from Arduino?
Power
The Mega 2560 can be powered via the USB connection or with an external power supply. The power source is selected automatically.
External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the boardās power jack. Leads from a battery can be inserted in the GND and Vin pin headers of the POWER connector.
The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may become unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.
The power pins are as follows:
Vin. The input voltage to the board when itās 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. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We donāt advise it.
3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.
GND. Ground pins.
IOREF. This pin on the board provides the voltage reference with which the microcontroller operates. A properly configured shield can read the IOREF pin voltage and select the appropriate power source or enable voltage translators on the outputs for working with the 5V or 3.3V.
I donāt want to power any thing from Arduino if I can avoid, but if it is safer to power things from arduino I want that. I donāt know how to discribe better.
Which implies it needs an input voltage of at least 6V.
According to that picture, all 5V pins are also outputs.
But to be sure, a better way is to verify it with the schematic of that PCB itself, or the arduino forum if you canāt find a schematic or documentation (which seems unlikely).
There are also variants of this PCB with an ATSAM processor, which runs at 3V3.
Rather depends what you want to do. Most shields use power from the Arduino to supply low power, logic functions. In you want to drive higher power devices that exceed the rating of the arduino, then the shield will need its own power supply. You will need to profile the power requirements for your board. So, a motor shield will likely have a mosfet driver and external power supply but a shield just interfacing an I2C sensor will likely just use the arduino supply.
I never worked with this board but remember there are āthingsā about this platform that would probably get better answers on the Arduino forum. I vaguely, sorta, kinda remember that if you have a 5V controlled source there maybe a pin you can use that bypasses the onboard regulator.
The point is, I think the folks on the Arduino Forum will answer questions you didnāt even know to ask. The sheer concentration of knowledge in one place makes it a valuable resource for what you are doing.
Iāve made well over 200 projects with Arduinoās (Uno, Nano, Mega, Teensy and Atmel-Chips(328, Tiny 13, 84, 85)).
Re Power:
Yes, connect All Grounds
Yes, Power from External (7 - 12 volts to VIN or Barrel-Jack). Powering in from USB is ok for low-level draw but, can cause issues with other pins (especially if output pins) best to avoid.
The Rest of the Power Pins?
ā¢ Do NOT power into to them!
ā¢ 3.3V and 5v are Output voltages to supply your attached gizmoās
ā¢ AREF is for Analog Ref (not for powering)
ā¢ IOREF is for I/O Ref (not for powering)
ā¢ Each output pin can supply not more than 40mA BUT, you can Gang them to provide multiples of 40mA)
If your attached gizmoās (sensorās, etc) can live with 3.3v and/or 5v at 40mA (per pin) then, best to use them on the Board for convenience and power the Arduino from a Wall-Wart/other supply to the Barrel jack or Vin.
Thereās a Mega board (shield) in the stock Templates panel. Once plugged in, itās difficult to unplug due to so many Pinsā¦
Photo of the Template belowā¦
ADDED: Example of Ganged Pins on UNO (for higher current output) Last Screenshot
EDIT: The Arduino IDE has several good Example Sketches that are very usable for testing your knowledge. Build simple BreadBoard circuit with them. By end-of-day, youāll be an expertā¦
ā¢ Your image shows Voltage incorrectly hooked up! Jumpers/Switchā¦ Rather than my posting what/how to do it, you will gain a firm/better understanding by reviewing Info Here
And, hereās a link to Pot Example
ā¢ Both Arduino and Poky have Vin and Vout so, be sure you donāt mix them (In/Out and Voltage levels) as you seem to currently be doing. Draw a hand sketch of whatās needed (before making the schematic, this will save time)ā¦
Pots use a range of voltages (depends on device/Resistanceā¦) and both Arduino and Pokey (pretty much all devices) can use typical Pots. Just need to set their Range (with respect to Digital Range (example: 5v/256 = 0.02v each incrementā¦ Or, as the Arduino example shows, 5/1023 = 0.005v/increment)
Some homework is needed - good support for this sort of stuff is found at many sitesā¦ This site is more about using Kicad to Build your designā¦
I have by mistake as you can see on the files I made, connected all 5 volt together. That is as I understand it wrong.
OK
If I understand correctly account to pokeys manual and 10 years of use of pokeys in simulator I should use 3.3 volt from pokeys, and the rest as I explained.
Then the question is arduino.
What Voltege source should I use from arduino?
Otherwise I think I have connected everything corect in the schematics if I seperat the power pins as you described.
Iāll leave everything to youā¦ but will answer the question above:
If needing power to Any Device (Pokey, Sensorsā¦etc) you can grab either or both 3.3v and/or 5v from the Arduino. Just donāt Mix voltages and In/outā¦
Power the Pokey from Arduinoās 5v.
EDIT: You ShouldNOT have Vin and USB hooked up at the same time! (on Arduinoās) EDIT: Be sure to use the Pokey with desired Input Voltage levelā¦ Last screenshot
USB powering is for convenience testing and Programming. Real power (to Arduino and attached devices should come from Vin. Unplug the USB cable when powering Vin
EDIT-ADDED: Simple screenshot to convey the Powering (you can have the Grounds connected or also have it switchable (I wouldnāt bother to do thatā¦). And, before you ask, āYesā you can use the 3.3v out and 5v out at the same time (on different devices, of course)
You can have them Connected at same time BUT, the Arduino senses it and will auto-select the External Power. Best to Google this kind of stuff and use Arduino site. This will helpā¦
Sorry but, below Quote cautions me re your knowledgeā¦ (no offense intendedā¦)
You decide (based on a handful of considerationsā¦). 3.3 and 5.0 yield different resolutions - thus, software changes/etcā¦ So, answer depends on what your design needsā¦
And, notice the 57E has two Versions - only 1.2 accepts higher voltage.
I would need too much background study to understand most of this discussion. I do not know what are āpokeysā but the answer to that question would probably lead me to another question.
However, in simple terms you can theoretically power a load (such as 5V @ 2 Amps) from one of several input sources by using āORing diodesā.to automatically select the highest voltage source. The issue with that is the diodes will waste 300 mV to 700 mV (sort of a typical range) depending on whether you use schottky or general purpose silicon diodes. This voltage drop can be virtually eliminated with any one of several āideal diodeā circuits. A discrete version of this uses op amps and MOSFETs. If a higher bias voltage (such as 12V) is available it can use Nch MOSFETs. If the bias voltage is not available, then the design can use ālow threshold voltageā Pch MOSFETs.
