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Apologies for the title gore and whether this seems to be a fairly basic question, I'm an Arduino noob.

I'm working on a wearable sensor system project at my university using an Arduino UNO R3 to handle all the sensors and power them. I'm currently powering the board with a USB connection and will be powering my components from the board's 5V pin as they can all safely operate with that voltage. The individual components do not exceed their I/O pins max current and their combined current usage doesn't exceed the boards maximum current.

My question comes in here: in the past if I've needed to connect multiple components to the ground and 5V pins of an Arduino board, I was always taught to use a matrix board to solder my component's 5V and GND wires to, where they could then be powered from two soldered wires from the microcontrollers 5V and GND pins.

Given that this is a wearable system, I would like to minimise any unnecessary hardware and so proposed to my supervisor that we cut out the matrix board and simply solder the VCC wires of the components together to one header pin which we can then plug into the 5V pin on the board to draw power. He strongly cautioned against this but wasn't able to provide a concrete reason as to why it would be a problem; as far as I can see the fundamental theory is the same and we are simply cutting out an unnecessary middle man.

Is there something I'm missing here or does this solution seem like it would work fine? Additionally, if this solution works for VCC, would the same principle work for sharing a grounded connection?

  • I would suggest you look for a supervisor who understands circuit theory. He/she may simply be sceptical about your soldering ability, but should be able to rationalise any valid concerns. – Milliways Dec 11 '17 at 10:37
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    I don't see a problem with splicing together all the power pins. The problem here is that single pins don't connect very solidly to the Arduino's pin headers, and can easily come out. Especially with a wearable project. I'd suggest getting a cheap proto-shield, and soldering all the wires of the components to that (maybe add some hot-melt glue for strain-relief). Then you can just press the shield onto the Arduino, and get a very solid (and reliable) connection. – Gerben Dec 11 '17 at 10:40
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Assuming you have suitable soldering skill, there are some considerations when you solder lots of wires to one header:

  • Lots of wires means lots of weight. The strain of several wires may degrade your connection or header over time, especially for a wearable system, where I assume the parts would be subject to some movement.
  • The width of the connection when all the wires are soldered to it. It might touch adjacent pins, or lean on them, creating mechanical stress. Heatshrink or sleeving can help with the electrical contact issue, but won't remove the mechanical risk.
  • Lots of wires soldered to one point may make the system more difficult to service. Instead of desoldering the wire to one component, you have to either desolder them all, or cut the wire to the one suspect component and then solder together wire stubs later to replace it.

When referring specifically to power supply pins, you'll need to consider the peak current requirements of anything you power from it. Based on https://playground.arduino.cc/Main/ArduinoPinCurrentLimitations it seems like you shouldn't be pulling more than 200mA from the Vcc PIN. Check the maximum current draw of all of your components that you want to power, add them together, and make sure it's under the limit of the Arduino board.

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