I am working with a Sainsmart Uno with SVG header pins. This header is really convenient for hooking a servo to directly, so I have two servos connected to it on D9 and D10 and a 9v battery supplying power via the power jack.

Everything seems to work fine at first, but eventually (sometimes quickly), the board becomes unresponsive. If, instead, I wire my servos to use the 5v pin on the Arduino (not from this SVG header), I don't run into this trouble.

Does anyone know if I am running into a limitation of this header Voltage pin? Has anyone had any success using this mechanism to drive servos? Certainly, I don't NEED to do it this way, but it sure is convenient.

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    Do you have a multimeter? Can you check where the voltage on that pin comes from? Looking online it seems there is a 5V and a 3.3V regulator. The 5V can supply 500mA, but the 3.3V only 50mA. Therefore it is the 3.3V going to the servos it is not enough. There is a switch on the front of the board that looks like it may change the voltage over. Commented Aug 10, 2014 at 2:25
  • Yes. Good question @geometrikal. I have the board switched into 5v mode, and the "V" pin on the header is reading as 5v. But this pin switches based on the board voltage setting, which is different from the specific 5v and 3.3v pins on the other side of the board. Perhaps, because the SVG pins can switch between 3.3v and 5v dynamically, they could have limited it to 50mA. That is my working hypotheses right now :) Commented Aug 11, 2014 at 3:23
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    It's probably best not to power your servos from the Arduino's regulator anyway, as servos are both power hungry and notoriously noisy. Give them there own 5v regulator, and connect the grounds in common. Commented Aug 11, 2014 at 19:04
  • @ChrisStratton Yeah, that makes sense. I just wonder what the utility of these SVG-style headers are if you can't plug a servo into them... but what you say makes sense. That is how I have it wired right now anyways. I was just hoping to use these headers. They are sooooo convenient. Commented Aug 12, 2014 at 19:41


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