My Mega 2560 Won't Start Up

I'm trying to troubleshoot my Arduino Mega 2560, and I need a little help.

I have a Mega 2560, and two Seeduino shields: the SD Card Shield and the TouchScreen Shield, stacked one on another in that order. When I plug the Mega into my MacBook, the power LED turns on and the link LED blinks. Additionally, the TouchScreen glows white. I have reset the board and installed a simple program to draw a couple of shapes on the TouchScreen with no errors from the Arduino software.

When I unplug the USB cable and plug it back in, the software I've just installed doesn't run. (I don't know if the software is supposed to run when it's plugged into the USB or not.) Also, I've plugged a multimode DC adapter into the power plug with the USB cable unplugged. The adapter is rated at 1 amp. On no voltage between 9 and 12 volts does the power LED turn on or does the software appear to run. I've also tried a 9 volt 800mA DC adapter as well. The power LED doesn't come on, nor does the software appear run. (I.e. no shapes appear on the TouchScreen.)

Part of the problem is that I don't know what's supposed to happen when you plug it in. Is the power LED supposed to come on out of the box? Do I need to jump any pins? Should I try to update the firmware? If the board is supposed to turn on out of the box with no modifications, and it isn't doing so, I think I may know what the problem is, and I'll need some advice about that. If not, I need to know what I need to do to get the thing to turn on.

If it's supposed to run out of the box, perhaps the problem is the power adapter. I'm building a four-channel audio field recording device (though at the moment it will only be able to handle two channels). I've physically attached a Sparkfun PCM1803A (see here) to the device. The voltage rating of the PCM1803A is similar to the Arduino, so I had someone solder a jumper cable between the ground and VCC pins of the PCM1803A directly to the female power jack on the Arduino. I'm thinking perhaps this is causing the problem. Perhaps either 1 amp isn't enough, or there's some kind of voltage drain of both devices which causes the Arduino to think there's a short and power down. But again, I need to know what the board is supposed to do in the first place to determine what the problem is.

Can anyone help?

What normally happens is it enters the bootloader for a second or so to see if a new program is waiting to be uploaded. If not, it then runs the existing program (if any).

You don't need to jumper anything and you don't normally need to upload the firmware (bootloader).

In other words, we've narrowed it down to being a problem with the power supply. Now I need to know if I need a more powerful power supply, or to disconnect the second device.

Thank you.

Post the photos - and a diagram of what you are connecting.

Paul__B:
Post the photos - and a diagram of what you are connecting.

You clearly need to break down this problem.

As I follow it so far, you have been able to power the Arduino successfully via the USB connection albeit it does not seem to be quite working correctly, but not by the coaxial power jack using what I gather is a multi-voltage power adapter.

Complicating this matter is that you have had someone else firmly solder the Vcc and ground of your PCM1803A module to the coaxial power jack of the Arduino so that you cannot power one without the other.

So ...

A one amp power adaptor is plenty to power both. It would be of interest to know whether this is one of the more recent switchmode adapters which have reasonably regulated voltage output, or the (heavier) mains transformer types which have wildly varying voltage output, though some did occasionally contain a linear regulator.

As in other discussions here, you need a multimeter. Nowadays these are digital, and adequate ones may be had for in the order of $5. You need to test the polarity of the power adapter; it should be positive on the centre sleeve and negative on the outer. Grabbing the nearest Arduino here, I observe that your photo appears to show the black wire connected to the side contact of the power jack which is in fact grounded on the PCB, and the white wire is not clear, but presumably connects to the end contact of the power jack which is Vin.

The only likely reason for your problem that I can see is that either the adapter has been set to the wrong polarity, or you have the connections between Arduino and PCM1803A crossed. If you find the adapter is indeed of the correct polarity, and the connections between the board are not crossed, you really need to disconnect the PCM1803A and see if the Arduino then works from the adapter. And of course, with the shields unmounted.

Another thing to check is that there is no "short" between the contacts where the wires were soldered on the back of that power socket (not hard to accidently create a "bridge" with solder that would create a "short"). If so this would short circuit the socket and thus the power supply. Electricity always tries to take the shortest/easiest path to ground and thus if the socket is short circuited, then none would flow through to the arduino.