Hello All,
Electronics Used:
Arduino Uno
3x QRE1113 Analog Sensors @5v
I am working on a project where I have 3 QRE1113 Analog Sensor Breakouts (https://www.sparkfun.com/products/9453), each draw 25mA. I have powered a single sensor at 5v from the 5v pin on an Arduino Uno board while the board is being supplied by the USB type - B connector.
My question is, how much can I draw from the 5v pin provided I am powering the board with a 9v battery?
(Total Draw 75mA, Supply Voltage 9v)
5v pin on an Arduino Uno board while the board is being supplied by the USB type - B connector.
USB standard is 500ma.
My question is, how much can I draw from the 5v pin provided I am powering the board with a 9v battery?
The onboard voltage regulator should be able to handle 500ma 1amp, (but I don't like drawing more than 250 ma without keeping an eye on it for a few minutes). The standard square 9volt is going to be your limiting factor. You'll probably be lucky to get 75ma out of it for any extended length of time. Regulator will handle it, but the battery wont last long.
The on board regulator has a series diode in the circuit, that is rated at 1A, that is the limit from the 5V pin / regulator.
Mind you from a 9V battery it will last all of three seconds if you are lucky.
These batteries are rubbish and should not be used.
Thanks guys, you really helped me sort this out.
Standard alkaline or NiMH 9V batteries both have a capacity around 325mAh at that sort of current (75mA), so expect it to last around 4 hours. Lithium ones have higher capacity (800 to 1200mAh), but are a lot more expensive. AA cells are much more economical for that sort of current drain.
The limiting factor controlling how much current you can draw from Vout when powering the Arduino from Vin or the barrel jack is generally the power dissipation in the regulator. At 75mA total current the dissipation will be around (9 - 5) * 75 = 300mW, which is within its limits. It will run warm but not hot.