Hey Everyone, I'm working on my first Arduino project after taking a 2 year hiatus and had a really quick question about powering up the Arduino Duemilanove.
I have some code uploaded onto the Arduino and it works perfectly when I have it plugged into my laptop via USB (as power), but when I plug the Arduino into an iPod wall wart with the USB cord, the circuit no longer acts properly.
I'm not exactly sure what's wrong, but could it be that the power coming from the computer's USB is DC whereas the iPod wall wart is AC? Any help would be great and please do excuse the n00bness.
Thanks guys for the help. I just double checked with the specs and it reads Input: AC 100-240 volts (V), 50/60 hertz (Hz) / Output: DC 5V, 1 A. Going to tap directly into the 5V slot and see how that goes. I currently have the power connected via the 3v3 slot.
genelu:
Thanks guys for the help. I just double checked with the specs and it reads Input: AC 100-240 volts (V), 50/60 hertz (Hz) / Output: DC 5V, 1 A. Going to tap directly into the 5V slot and see how that goes. I currently have the power connected via the 3v3 slot.
I'm not clear how you're connecting the wallwart. From your original post I thought you were using a USB output (USB charger type of thing) and I assumed you'd connect that to the USB port on the nano. (I've got half a dozen nanos running like that without any problem.) Doesn't your wallwart provide a 5V output terminated with a USB plug?
I would use the USB to run the Arduino and the other as external power for whatever was dragging the Arduino down.. just connect the grounds from each.
genelu:
Thanks guys for the help. I just double checked with the specs and it reads Input: AC 100-240 volts (V), 50/60 hertz (Hz) / Output: DC 5V, 1 A. Going to tap directly into the 5V slot and see how that goes. I currently have the power connected via the 3v3 slot.
I'm not clear how you're connecting the wallwart. From your original post I thought you were using a USB output (USB charger type of thing) and I assumed you'd connect that to the USB port on the nano. (I've got half a dozen nanos running like that without any problem.) Doesn't your wallwart provide a 5V output terminated with a USB plug?
It's even simpler than that, what I initially did was use the USB cable to connect from my arduino to an iPod wall wart. Before this, I had the Arduino board powered thru the laptop, which I'm assuming is around 3V. To restate the problem, after hooking up the Arduino to the iPod wall wart, the output on the Arduino seemed a bit off. The phototransistor that I was using became unstable and LEDs were turning on when they weren't supposed to be turning on. After some further testing, I think it's just because I wasn't considering the jump in voltage. Does this sound like the right assumption?
CrossRoads:
USB puts out 5V.
If you're trying to power the board by reverse driving thru the 3.3V regulator, then yeah, you're likely to have problems.
Haven't looked at the circuit, but I wouldn't be surprised if back-feeding 5V through the 3V3 regulator let the smoke out.
Just a note for any listening, many switching regulators require at least 5% load in order to regulate, while out of load range voltages soar until a power balance is established somewhere.....aka the smoing diodes....
Panici:
What happens if you don't connect the grounds?
It depends on how different the ground of one is from the ground of the other and where the power is connected. Volts has meaning with relation to ground. If grounds get far enough apart, something gets more voltage or current than it can safely handle and then it goes out for a smoke.
Panici:
What happens if you don't connect the grounds?
It depends on how different the ground of one is from the ground of the other and where the power is connected. Volts has meaning with relation to ground. If grounds get far enough apart, something gets more voltage or current than it can safely handle and then it goes out for a smoke.
Ah that makes sense.
So how do I physically connect the +5v from the external power supply to the arduino? I see my MEGA has a Vin PIN. What about on a Nano?
Some observations from a 40 year vet in the business...
Always connect the grounds between any galvanically connected (current flows between them) devices. This is a requirement. If they are optically or inductively isolated, then do not connect the grounds.
Use USB power only when little or nothing is connected to your device and even then only if there is no other choice. Stable power is essential to success in electronics, especially digital electronics. It is far easier just to adopt a professional approach when it comes to supplying power to your experiments, than it is to search for endless hours trying to figure out why things don't work right.. For Arduinos, USB power is usually fine if you are just using it for programming, but a mistake if you are supplying power from the Arduino to anything else. Arduinos are very minimal boards and have very little in the way of noise suppression on them. My recommendation is, use a 9v switchmode wall-wart capable of at least 1 amp. Apply this power either through the DC power jack (on the larger boards) or to the Vin/9v on the Nano/Mini boards. This way it at least goes through the board's regulator.
If you are expecting to use motor driven actuators (Servos, DC motors, Stepper motors, etc...) or anything but the smallest relays, it is highly recommended to supply those devices, and their drive circuitry, with a separate power source. In addition I strongly recommend you use optical isolation between the controller and the drive circuitry.
As already noted, Arduinos (and the Sheilds, bricks, etc...) have minimal noise suppression built into them. This makes them even more susceptible to poor power. Accordingly, I recommend that any add-on circuitry you design to attach to these controllers should consider the Ardunio as a source of noise and treat the signals and power coming from it accordingly. This is especially so if teh power to the Arduino itself is marginal.
Panici:
What happens if you don't connect the grounds?
It depends on how different the ground of one is from the ground of the other and where the power is connected. Volts has meaning with relation to ground. If grounds get far enough apart, something gets more voltage or current than it can safely handle and then it goes out for a smoke.
First you connect the grounds....
Ah that makes sense.
So how do I physically connect the +5v from the external power supply to the arduino? I see my MEGA has a Vin PIN. What about on a Nano?
