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1  Using Arduino / Project Guidance / Re: 5V from USB on Nano 3.0 on: June 23, 2013, 03:14:27 pm
Measured 70mA + whatever the Arduino draws. Already jumpered the diode, still haven't tested with the sensor but everything else seems to be working OK.
2  Using Arduino / Project Guidance / Re: 5V from USB on Nano 3.0 on: June 23, 2013, 07:53:47 am
@zoomkat: No, I'm not willing to risk damage to my computer (OTOH I'm willing to risk damage to the Arduino). I'm posting because I don't really see any way for this to damage my computer, considering the Nano will stay in the project forever and will never receive any other kind of power. But then again I'd like to know if someone sees any way this could damage the computer.

@CrossRoads: thanks, jumpering might be a better idea indeed.

Let me add more details to what I'm doing. I'm powering a VASD1-S5-D15-SIP 5V to 15V DC/DC converter (it's minimum voltage is 4.5V and under load it gets very close to that, which is why I want the diode gone), which in turns powers a pair of 7810/7910 regulators, which power a smart sensor that requires a split supply and an external ADC (decoupling caps/resistors and other details ommitted).
3  Using Arduino / Project Guidance / 5V from USB on Nano 3.0 on: June 22, 2013, 10:08:28 pm
I need to draw some current from USB through an Arduino Nano to power some external stuff (about 100mA). Problem is that it needs to be very close to 5V and the Nano has a diode between the USB+ and the 5V pin that drops the voltage to 4.6-4.7V. I'm thinking about replacing the diode with a wire but I'd like to ask if there's a good reason I shouldn't do that... This Arduino will never be powered from anything but USB.
4  Using Arduino / Sensors / Re: Safety of going over AREF on: November 13, 2012, 02:19:29 pm
Cool, that's perfect. I'm using a Mega and that internal 2.56V will do a great job!

Thanks guys!
5  Using Arduino / Sensors / Safety of going over AREF on: November 13, 2012, 01:04:14 pm
I have an A1302 hall effect sensor that outputs an analog voltage proportional to the magnetic field. I'm mostly interested on lower field values (of the same polarity) and I'd like to increase sensitivity while decreasing range. I'm thinking about feeding a 2.5V to the AREF pin, which would effective double the resolution over the 0-2.5V range.

My question is what happens if the sensor outputs a voltage higher than AREF on an analog pin - will it cap the value, overflow like a variable or burn the ATMega?
Don't wanna try before asking for obvious reasons smiley-wink
6  Using Arduino / Motors, Mechanics, and Power / Re: Problem with L298N and motors on: October 23, 2012, 07:54:19 am
Sorry about the links, fixed.

I'm powering the motor from 2 16340 batteries (3.7V each). I've tried powering both arduino and H-bridge from the batteries and just the H-bridge with the grounds connected. Makes no difference.

The motor has no caps, it looks like this. I'll try soldering some caps but I'll have to go shopping first.

AFAIK there are no jumpers to set the power source.. Shouldn't be a problem since the only wires connecting the arduino to the bridge are the 3 signals and the common ground. That 5V_EN jumper is to disable the regulator (haven't tried that since I'll need to supply 5V externally).

I might try to add that missing cap, might help since it's between the 5V and gnd rails.

I also noted that this board has pull-up resistors for every signal rail, most can be disabled but the ones for the enable pins cannot. Can this get interference back to the Arduino? Should I cut the rails?
7  Using Arduino / Motors, Mechanics, and Power / Problem with L298N and motors on: October 22, 2012, 05:40:40 pm
I have this DX H-bridge board, which seems to be an exact clone of this one.

I was using it to switch an electromagnet and it works fine as long as I keep the EM away from other USB peripherals. If it's too near the peripherals pick up a lot of interference and stop working until I reconnect.

Now I'm trying to power a small "toy car" DC motor with it - the motor's been harvested a long time ago and has no datasheet or markings but it looks like a 3V motor.
I connected the three control pins to the arduino and used a pot to control speed (PWM < 127 on enable pin to avoid frying the motor) and direction. I'm using 2x16340 batteries for the motor power and USB for the arduino, with the grounds connected.

The interference is so high it's making the computer's USB malfunction even with the motor 1m away. After a couple seconds playing with the pot the serial monitor on the computer stops receiving data (the analog reading of the pot) and I have to reconnect to make it work again, can't even upload a sketch after it "crashes".

I stopped experimenting with this because I'm afraid it'll damage the computer.

Am I doing something wrong? Is there a problem with the H-bridge board or is this normal?
8  Using Arduino / Installation & Troubleshooting / Re: Arduino Mega heating up on: October 22, 2012, 05:21:33 pm
Double checked everything, I guess it's fine indeed. Thanks!
9  Using Arduino / Installation & Troubleshooting / Re: Arduino Mega heating up on: October 21, 2012, 09:07:52 pm
Good to know, thanks! Do you think the heating is normal as well?
10  Using Arduino / Installation & Troubleshooting / Arduino Mega heating up on: October 21, 2012, 03:42:28 pm
I purchased an Arduino Mega 2560 clone and I believe the ATMega2560 is heating up too much (my Uno doesn't heat up at all).
Powered it from USB and tested with nothing connected, running a sketch that loops some math. Measuring with an IR thermometer I get about 39ºC (the rest of the board is around 30ºC and ambient is 27ºC).

Other than that it seems to be OK, I even tested every pin (as input and output) and they all work fine.
Also tested from a 9V battery and the board draws ~80mA with nothing connected.

Do you guys think this is an issue or should I just ignore it? If it's a latent issue that'll show up later I'd rather know now so I can request an RMA.
Is there any other test I can/should run?

Thanks in advance!
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