MobiFlight Community Support

Welcome to the forum for MobiFlight! Feel free to reach out to the community in case you have questions, issues or just want to share great ideas or details about your latest home cockpit project.

You like MobiFlight? Donate via PayPal and support the MobiFlight development. Thanks! 

icon
Avatar
Woutex
Posts: 1
Hello finally made an account here!
Did some research for a future project which will include leds and 7 segment displays, I know that I need a power supply to get sufficient power for leds, 7 segment displays etc.
My question: can I plug in a wall plug bullet connector (with the correct voltage) in the Arduino Mega board and will that be sufficient and correctly handled by the Arduino?

Kind regards,

Wouter Bakker
2019-11-11 23:45
Avatar
pizman82
Moderator
From: ETSI, Germany
Posts: 2916
Supporter
Hi

Most Power is needed for Motors.
LED are mostly low current..... Also 7Seg work in a system that only one Digit is light at a time ( With a verry high frequency so it looks like all are on) . that means Whatever you build a full Cockpit with hundrets of (Low current) LED and some Displays you will not get a power problem with simple USB Power.

Most users just protect the internal Power of there PC by using a USB Hub with a external suply.... So the 500mA per USB Connector come basicly from the maby 2A Suply on the Hub.

Sure.... I also heard about users who power there Megas directly by the Power Input slot..... But i also hear about lots of people with complex Cockpits and 20+ Arduinos that are using just the Hubs i said.
Only note..... Motors can be problematic. Here it is usefull to have a external 5V suply that power the motor itself.

Maby Stephan ( our Electronic Pro ) can give you more information here...
Good Luck !
2019-11-11 23:53
Avatar
StephanHo
From: EDDG, Germany
Posts: 1365
Supporter
Hi,

actually pizman has already said the essentials.

To be on the safe side, when using larger power consumers (steppers, servos, relays) should always rely on an external power supply.
Their use is in principle uncritical. It is only necessary to connect the GND terminal of the external power supply to the GND of the controlling MEGA.

Although a MEGA can deliver up to 800 mA of power, but also here it is like the car. The car is not driven in the performance in the red area. For continuous operation, the average green range should be considered, which would be between 400 and 500 mA for the MEGA. If more is needed, it should be considered to distribute the load over several MEGAs or to use an external power supply. So please do not save at the wrong point. The components will thank you.
Grüße,
Stephan
2019-11-12 11:23
Avatar
pluckas
Posts: 63
Supporter
Hi Stephan,

Electronics question:

I have been building some stepper driven gauges, connecting the 4 control wires to the Mega, and the power wires directly to a 5V power supply. Things seem to work fine. Why would I need to also connect the ground to the Mega?

Paul
2019-11-13 11:26
Avatar
pizman82
Moderator
From: ETSI, Germany
Posts: 2916
Supporter
Stephan can explane this pretty sure much more better as me.

In simple words...... the Controller ULN2003 gets power from your supply..... But also is connected via Data Lines from Arduino. And this datalines basicly also send a electrical voltage.
So then you have 2 different GRD potentials in one system.... And as i know this is bad.

Thats the same reason why Stephan also recommend to wire all Used megas together by one GRD Loop..... Then its no longer important to use the GRD from the same Arduino where you set the Pin..... Then all Grounds are simmular.
Good Luck !
2019-11-13 12:49
Avatar
StephanHo
From: EDDG, Germany
Posts: 1365
Supporter
Exactly!

Cooperating electronic components need a common GND potential.

Basically, a common potential of an electronic circuit is referred to as GND or ground. Previously it was said to 0 volts or minus, the opposite pole was called plus or just any voltage greater than 0V.

If you put only one output from the same circuit (say 5V) to the input of another circuit, what happens? Nothing. Because these 5V have no relation to the input circuit, to what?

So you can connect to a circuit that works with 5V, easily the + pole of a 9 or 12V battery, but ONLY the positive pole. Nothing happens! Why? This tension has no relation. Result: Applying the positive pole has no effect. But if you put the negative terminal of the battery on the GND of the 5V circuit, then both the battery and the 5V circuit have a common potential: 0V or just GND. An absolutely undesirable result in this specific case!

Even more banal: you want to connect a microphone to the PC. Not an issue, but what do you need? Exactly, 2 connections. A line for the common potential and a line that transmits the AC voltage of the microphone. If the common potential is missing, the receiver circuit can not do anything with the "data" of the microphone. As well as? Therefore, the base potential is used, called GND, a common reference potential and already the "data" can be processed on the other side.

For a PC, this can be different. All plugged-in components reach the GND potential via the USB connectors and are thus connected to each other. But if an external power supply is added, it does not automatically have GND potential for the PC or its connected components. So, the GND of the external power supply must be connected to the GND of the computer components so that there is also a common reference potential here.

Flying often uses two terms: one time GRD and the other GND. GRD is not an electrical reference potential to exclude interchanges, but the simple ground on which people stand, while GND is the electrical or electronic term for the common reference potential.

So, I hope to have contributed to the general confusion ;)
Grüße,
Stephan
2019-11-13 13:53
Avatar
auransbey
From: ROME, Italy
Posts: 53
Good morning dear friends,
I connect to the intervention of Stephan n. 15521.
Stephan says that it is necessary to connect the GND of the external power supply to the GND of the mega card.
I checked and I verified that inside the mega card the 2 GNDs are already connected in parallel.
I wonder if it is still necessary to connect the 2 GNDs?
I have 9 megs powered externally at 9.9 volts from a single power supply.
if Stephan thinks it's necessary, I'll connect all the GNDs together.
thanks for your answer.
MF - simply wonderful !!
2019-11-21 12:15
Avatar
pizman82
Moderator
From: ETSI, Germany
Posts: 2916
Supporter
You Missunderstand !

He not mean you should share grounds in your special situation.

Stephan, myself and many other uers NOT use a external Power suply to power the MEGAS directly ( via the round port nearby the USB connector) like YOU do.
Normaly we all use simply USB Power and let this port empty.
The Power itself comes from Computer ( 500mA via USB ) OR we use USB-Hubs that have a "own" Power suply.... But also with the Hubs the Power to Mega is done via USB....... The Only difference is that the Power not com from Computer..... It Come from the Hub.

What Stephan recommend and mean is that he use a External Suply (Pretty sure 5V ) to power elements with a high ammount of Power like Stepper Motors.
So The Stepper is set to a ULN2003 Controller..... And the Controller is set to the MEGA .....
BUT only the Data Lines ! The 5V and GRD from ULN Board is connected to the External Suply !

In Simple words.... All stuff, that need a 5V Input like Motors can be powerd directly by a Powersuply from THAT 5V lines...... BUT to get sure also the Datalines work fine you must share the GRD of the Mega and the Power suply.
Good Luck !
2019-11-21 16:41
Avatar
auransbey
From: ROME, Italy
Posts: 53
I think I understood perfectly.
thanks for the clarification.
MF - simply wonderful !!
2019-11-21 21:09
icon