hi,
I used Arduino mega2560 board. I connected the board with 5V power adaptor at arduino power jacket, and also connect it with computer with USB. The I used the 5V pin as power supply for a simple circuit.
After a while, I found that my mega board can't only output 3.6V voltage at its digital output pins, as well as the 5V pin. I measured the voltage directly with multimeter.
Is my board damaged? what was wrong?
thank you.
Disconnect the mega2560 from all circuitry, then connect only the power adapter at the power jack. Measure voltage between the Vin pin and GND, and measure between the 5V pin and GND, and tell us what you see on the voltmeter.
I connected 9v power adaptor to the power jacket.
Vin pin: 7.46V
5V pin: 4.0V
If I connected 5V power adaptor to the jacket:
Vin Pin: 4.17V
5V pin:3.13
I measured the power adaptors and USB, the voltage output is correct. Before the problem, I used the 5V pin as 5V supply to power L293D Vcc1, enable pins.
I think the 4.17 V at the Vin pin means the 5V power adapter is supplying too little voltage. If it is a regulated 5V power supply you can simply attach it to the 5V pin and GND. That would bypass the Mega 2560's onboard voltage regulator.
I'm not sure if attaching the 9V power adapter to the power jack and the 5V pin showing 4.0V is normal. I would expect it to be closer to 5V. I have seen inaccurate multimeters, though.
When using with the 9V adapter, are any parts on the board warm or hot to the touch?
I suppose you could have overloaded the onboard regulator.
before the problem, I have some LEDs connected, the brightness is correct. I only used 5V power adaptor to connect to the jacket before the problem even thought arduino manual say the Jacket can connect with >6V power adaptor.
No any part of the board warm or hot when connecting 9V adaptor at the jacket.
The multimeter is accurate because it measured the correct output of 5V, 9V power adaptor and 5V USB.
the Leds become very dim after the problem.
Hmmm. Well I'm thinking if it were my board I would try replacing the regulator first. If your board is one with the ATmega16U2 USB-to-serial chip, then the schematic is here:
The regulator:
http://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeyNCP1117ST50T3G
It should be relatively inexpensive to try.
If you have any of those cheap Chinese Nano boards with the CH340G chip that you have blown things like the main processor, but the regulator is still good on it, you can salvage the regulator and put it on the Mega board. I keep a bag of broken boards and modules to salvage parts off of.
You could also ignore the problem and just not use the Vin or barrel jack. When not connected to your computer, you can power it with a USB cable and an iPhone charging block which has the USB connector on it.
You can't connect a 5V adaptor to the "Power input" jack - the regulator causes several volts of voltage drop, which is why the jack is specified for 7V min. You should be able to put 5V in via the USB jack, or via the "5V" pin.
westfw:
You can't connect a 5V adaptor to the "Power input" jack - the regulator causes several volts of voltage drop, which is why the jack is specified for 7V min. You should be able to put 5V in via the USB jack, or via the "5V" pin.
Yeah true. I'm thinking that there should be a formal web page that clearly provides details about what supply voltages are recommended, and where to apply it.
I have seen information that says vague things like:
"input voltage": 7 to 12 V.
"operating voltage": 5 V <- This is totally vague.
Things like that might mean something clear to who-ever designed it. But is completely vague when it comes to a user reading stuff like that.
Clear means - "Input DC jack supply voltage: 7 to 12V DC, with power rating = XX Watt".
"USB power may be used, provided that maximum power output of the USB power source is not exceeded etc etc."
There is a schematic... that has things like PWR IN, and Vin and USB-Vcc etc. The Input DC jack is PWR IN. And then there's the confusing things like the "Vin" pin. So some people reading the schematics will probably wonder what's all this PWR IN and Vin etc.
Thank you, I see. I have replaced a new Mega board. It is good to know better about the board in this thread.
best