Go Down

Topic: Power Arduino and LED Matrix (Read 3843 times) previous topic - next topic

GaryF

I'm doing a project involving an Arduino and a 32x32 LED matrix. I'd like to power this using one DC power adapter. For the LED matrix they recommend a 5V 2A DC adapter.

Is the Arduino able to output 5V 2A if I for example get a 12V 3A DC adapter to power the Arduino? Or do you recommend me solving this differently?

joemcder

Quote
Is the Arduino able to output 5V 2A if I for example get a 12V 3A DC adapter to power the Arduino?


Definitely not. Your Arduino will be toast.

You can probably power your Arduino from the led 5 volt supply bypassing the regulator.  What Arduino are you using?  You may need an additional electrolytic & ceramic capacitor to filter the supply if the led circuits generate too much noise.  Two seperate supplies will obviously solve the problem but this is often not necessary.


GaryF

Thanks. I'm probably gonna use an Arduino Mega. About the bypassing: Doesn't the Arduino want more than 5V?

runaway_pancake


Doesn't the Arduino want more than 5V?


Not if you connect that to "+5".
[N.B. When so doing, nothing should be connected to Vin and/or the "DC-in" barrel jack]
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

joemcder

Notice that your Arduino boards have connections labelled 5V+.  If you leave the main power connector unused, any 5v supply on this pin powers the board.  I do this all the time.  I'm sure the Mega is similar.  Be careful that it is 5v and only 5v. No protection against reversing leads.

Someone with Mega experience will hopefully comment.


GaryF



Doesn't the Arduino want more than 5V?

Not if you connect that to "+5".
[N.B. When so doing, nothing should be connected to Vin and/or the "DC-in" barrel jack]


Notice that your Arduino boards have connections labelled 5V+.  If you leave the main power connector unused, any 5v supply on this pin powers the board.  I do this all the time.  I'm sure the Mega is similar.  Be careful that it is 5v and only 5v. No protection against reversing leads.

Someone with Mega experience will hopefully comment.

Okay, to be absolutely clear; I'm looking at my Uno, it is the connection 5V (that usually outputs 5V, the one between 3.3V and GND) you are talking about? In that case I don't see any problem with your first suggestion joe mcd (Taking 5V from adapter powering the leds, through a capacitor). I'd still like to hear anyone with Mega experience regarding this.

CrossRoads

Connect a 1N4001 type diode from 5V to Vin to avoid reverse driving the 5V regulator. The 1117 types can be damaged when reverse driven.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

GaryF

So I'm thinking this should work (see attached file):

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

GaryF

When powering the Arduino this way, I guess it's not good to connect it via USB for programming while having the external supply connected?

CrossRoads

Depends on your power connections. You will have the +5s isolated by diodes or something?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

GaryF


Depends on your power connections. You will have the +5s isolated by diodes or something?

Sorry for asking so many dumb questions but how would I properly do this?

The alternative I'm thinking is to modify a USB cable where I remove the USB VCC, but it's not as elegant.

CrossRoads

What you don't want is two 5V sources connected to each other.
Low Vf schottky diodes like this would do it.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

beny89

#13
Sep 25, 2013, 12:08 am Last Edit: Jul 18, 2014, 06:43 pm by beny89 Reason: 1
@GaryF why don't you simply use pull ups for the LED matrix and operate it using a low output levels from the Arduino. First of all, you should've chosen an LED matrix that inherently works on low voltage levels, by that I mean you select a row by given a 0V signal on an output pin of Arduino and rest of the time the LED is automatically pulled up. So basically the arduino acts as a sink. You can use current limiting resistors to ensure that your controller doesn't have to sink more current than specified in its datasheet. Now even if you have an LED matrix which operates on high voltage level, you can simply pull up the pins and use NOT-gate ICs with that to convert the signal to show a high. This might use a little more power but it's better than blowing up your controller. Do tell us what solution you used and what the current ratings were.

pcb fabrication

Go Up