I ran into an unusual problem when connecting the ground pin of my Arduino ATmega2560 to the ground of an external power source.
The Setup:
I want to control a servo-motor which draws up to 2.5A and therefore I've got a power supply that provides 5V with 12A (In a later stage 3 of those motors will be needed). For testing, my Arduino is powered through the USB port which enables me to use the Serial Monitor as well. I am using Windows 7. The power supplies output voltage is set to exactly 5.03V.
This is the motor: MG996R
And this is the external power supply: Power Supply
The Wiring:
The power lines of the motor are connected to the V+ and V- pins of the power supply and the control line is connected to pin 43 on my Arduino. The grounds are connected from the GND pin of the Arduino to the V- pin of the power supply.
The Problem:
When the connection between both grounds is established, the connection from my computer to the Arduino is lost (USB device disconnected sound is playing). Furthermore, the lights on the Arduino shine brighter. This made me measure the Arduinos output and it is about 7V on the 5V pin when the grounds are connected, which confused me quite a lot.
Also, I'm not using a jumper wire to connect the grounds but a thicker wire with multiple copper wires inside, because a normal jumper wire started to melt when connecting the grounds before.
I hope you can help me with my problem, best regards
If there is 7v on the 5v pin there is something seriously wrong and you should stop immediately.
You need to make a simple pencil drawing showing how you have everything connected and post a photo of the drawing. It is too easy to misunderstand verbal descriptions of wiring.
I am always suspicious of Fritzing diagrams because they put style before substance - which is why I asked you to do a pencil drawing. At least your Fritzing diagram is clear. I am assuming it represents YOUR connections and is not just a convenient diagram you found on the web.
The business of drawing a pencil diagram is usually a very good way of finding faults because it forces you to examine everything carefully.
Are you sure you have not mixed up the servo signal and GND wires? The power wire is the centre one.
I don't see anything wrong with your diagram. Have you any way to check if the servo is faulty.
Maybe try powering the servo with 3xAA cells (4.5v) which won't damage the Arduino.
...R
PS. For the future please don't add stuff to older Posts because it makes reading a Thread from top to bottom difficult. Correcting typos in older posts is fine.
Sorry, all the other wiring is currently not connected to anything. I was just too lazy to take it off. There is a rotary encoder and a light bridge involved in this project, but at the moment they are not connected to the Arduino.
Also, I'm not using a jumper wire to connect the grounds but a thicker wire with multiple copper wires inside, because a normal jumper wire started to melt when connecting the grounds before
That's because there is current flowing between the two terminals.
Is the 5 volt power supply connected to earth? Three wire plug?
Is your computer connected connected to earth? Three wire plug?
Is the computer on the same mains supply circuit as the 5 volt power supply?
If any answer above is no, STOP. Correct/change so you have three yes responses.
If you still have problem, with no power on, remove the jumper wire between the 5 volt supply and the Arduino. Power up. Being careful not to touch the terminals, use your voltmeter and measure between the terminals were the jumper had been connected. Check both AC and DC voltage ranges. Post your findings.
You have either missing earth connections or a bad power supply which could be either the 5 volt supply or the computer supply.
When measuring the voltage ranges between the terminals, I measured 5.03V DC and around 1V AC.
I tried something different and connected the 5V pin of the Arduino directly to the V+ terminal of the power supply without adding the USB connection to the computer. When doing this, the servo moves just as intended.
