Arduino won't power up via jack


I'm trying to build a puzzle for an EscapeRoom and I'm having some dificulties powering it.

The project consists of:

Arduino MEGA(clon) driving four BCD to seven segment decoders (SN74LS47N) wich drive 2 double digit common anode 7segments (220ohm resitors in between). There are also 4 12v LED push buttons that currently do nothing yet, but they are supposed to be used for the players to change the numbers in the 7 segments in order to set the correct password.

The problem I'm finding is that after having everything soldered and ready to start I tryed to power it with a 12v power supply through the jack on the arduino. At first it worked, but after a few seconds the 7 segments (wich were currently set by the program to display the 8 number) started to do strange things, like displaying a 4 or an A... a couple of seconds later it stoped working at all. Now, if I power it through the usb it seems to work just fine but it won't do anything through the jack (nothing lights up in the arduino).

I think I may have burnt the regulator, if that's possible at all. The components are powered this way: The 74LS47's take 5v from the arduino 5v pin. The 7 segments also take 5v from the arduino 5v pin(same pin). The 12v LED illuminated buttons take 12v from the VIN pin (I assume 5v when powered through the usb, a lot less powerful light)

And that's all.

Here are the technical info for each component:

SN74LS47N: OPD-D5630LE-BW (7 seg) Pushbuttons (82-5151.1143):

I'll try to attach a picture of it.

Lets see if I can attach the pictures now:

I just ralized maybe I should use one GND pin for the 5v and another for the 12v... may be it?

joancasas: I think I may have burnt the regulator, if that's possible at all.

Yes, that is entirely possible. A high voltage on the input and a reasonable current on the output will exceed the power dissipation of the regulator, even though the current is much less than the maximum current. It's not that the specification is wrong but you're looking at the wrong specification if you only look at current without considering power.

The solution is to get a bigger 5V regulator. Look at the range of regulators at Pololu for some ideas on what's available. Connect this to the 5V pin on the Arduino.

joancasas: I just ralized maybe I should use one GND pin for the 5v and another for the 12v... may be it?

No! Don't do that. Then any current that passes between the two grounds will pass through your Arduino board. It could melt the tracks. Always try to use 'star grounding' where all grounds come back to a common point. Only use one ground pin on the Arduino and connect that to the common ground.

Thank you Morgan!

So, for example, if I were to use this regulator: 5v 2.5A

I would have to put the 12v from the power supply in the VIN pin of the regulator and then power everything up from the out pin of the regulator.

The Arduino would also get powered connecting the 5v pin on the arduino to the out pin on the regulator, right?.


Thanks Morgan!! You Rock! :grin: :grin: ;)

Hi, Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png? Showing how you are powering the different PCBs and the mega?

Just a block for each display PCB would be fine.

Thanks.. Tom.. :) If you have not already drawn a schematic the now is the time.