I'm supplying power to the Arduino Uno Vin pin using the Sparkfun "Power Cell - LiPo Charger/Booster" from Proto-pic. My green On light is on. So far so good. This gives me a UPS for the Arduino and I want this to become my power source.
Now I want to plug in my USB connection to the PC to download some programmes, but I'm scared. I read somewhere that you must not have more than one power supply to the Arduino, and yet the USB used to be my power source. So when I plug the USB through to the PC will that make two power supplies to the Arduino? Is this a problem, and if so how do I stop the USB providing power while retaining its communication function?
You can have Vin/Barrel jack and USB connected at the same time.
This is what I wanted to hear - USB and Vin can both safely be connected at the same time. Then you say...
As long as Vin/Barrel jack is higher than 7.5V, the auto-select circuit will continue to power with the external adapter.
Now the sparkfun board produces exactly 5V, so am I right in concluding that my Arduino will take power from the 5V USB supply when it is connected, then switch to my 5V Vin supply when the USB connection is broken?
1. You should not connect a regulated 5V source to the 5V pin and power from USB at the same.
Now I'm getting worried again. Are you saying that I can connect a high voltage to Vin alongside the USB, but that I cannot connect 5V to Vin alongside the USB?
2. When you open / close the serial connection, your arduino will reset.
If I have downloaded and started my programme with the USB connected, and I want now to remove my PC from the scene, are you saying that my programme will be forced to re-start?
kenny_devon:
Now the sparkfun board produces exactly 5V, so am I right in concluding that my Arduino will take power from the 5V USB supply when it is connected, then switch to my 5V Vin supply when the USB connection is broken?
If it only provides 5V, you cannot connect it to Vin. Vin needs at least 7V to operate correctly. You cannot use that board and USB at the same time.
kenny_devon:
Now I'm getting worried again. Are you saying that I can connect a high voltage to Vin alongside the USB, but that I cannot connect 5V to Vin alongside the USB?
Correct. You cannot connect an external 5volt source to the 5V pin and USB at the same time.
kenny_devon:
2. When you open / close the serial connection, your arduino will reset.
and I want now to remove my PC from the scene, are you saying that my programme will be forced to re-start?
A RESET is generated when the serial port is accessed. So if you are using Serial Monitor, then yes, you will cause a reset when you disconnect the board / close the serial monitor.
Also, when quoting use [quote][/quote] tags, not tags.
Hi James,
Thanks. How then do I permanently connect an external 5V supply to power the Arduino, if not through Vin, given that I want to use the USB for programming?
Kenny
I can use a separate power source as long as it is more than 5V
Basically correct, although my reading of the schematics says that you need at least 6v6 for the circuit to switch to the VIN power which is what you want.
12V is really the upper limit for VIN, 7V the lower limit usually recommended. For thermal reasons it's better to be closer to 7 than 12 but depending on the current being drawn anything in that range should be OK.
Since the Arduino only takes 5V through the USB, and since I have a 5V UPS source, I'm going to try hooking up my UPS source to the USB port. Using a couple of USB breakout boards, I'm wiring in power from the UPS and data from the computer, into a single USB cable and feeding this to the Arduino. The power coming from the computer is simply ignored. Is this crazy? Wish me luck.