I've got a lot of good help with my new Arduino hobby from existing posts, but this one does not seem to have been asked before. Which probably means that the answer either is totally obvious or the question is silly to begin with, but I just want to be on the safe side.
The question is, as the subject says, is it OK to daisychain the 5v line (purely for power supply purpose) between components (or between multiple 5v inputs on the same component)? As opposed to going back to a PCB/breadboard for each input.
I know that it is fine for the ground connection, but googling "daisy chain 5v" in quotes throws up only a couple of arcade related pages showing it is sometimes done. I understand that doing this when you use 5v to control a motor (for example) or reading high/low, etc is totally out. What I want to do is use it for the basic power supply function only. I can't for the life of me (but I'm a beginner) see how this would be different than going back to the rail of the breadboard for every component, but I have never seen it done in sketches, diagrams, etc.
Basically I am using a plastic case that houses an Uno and a 16x2 characters LCD display. You can see it here. The wiring for the LCD shows that in this case it has 2 5v inputs. It is for a little game for my son, so I want to mod the case a bit and add the Dfplayer Mini to play MP3 files through a tiny 8 Ohm speaker inside the box. I'll also add 3-4 pushbuttons near the bottom of the box.
This doesn't leave so much space, so adding a protoshield of some sort is best avoided, the buttons I want to use would bump into it.
By and large, it makes sense for the power connections to track the data connections (or vice versa), so if a module connects directly to the Arduino, then its power connections should follow directly to the Arduino module. If you can daisy chain SPI or I2C devices physically, then the power connections should follow.
This is particularly important for output devices involving significant current. The relay boards are a frequent problem here, which is another matter but introduces the question of separate power supplies and where the grounds connect together. Maybe I will shy away from that just now ...
On a breadboard take the power and ground pins direct to the busbars along the edge of the
breadboard, but feel free to daisy chain from those pins per chip. And don't forget decoupling!
Thanks to all for quick and helpful replies! I have some thoughts/follow ups on the different responses before outlining a somewhat improved version of this.
weedpharma:
Daisy chaining power supply is ok as long as the current is not so high as to cause voltage drops on the wires.
If you are using the onboard 5v and any normal jumper size wire, you will not have a problem.
Thanks for confirming my thought that this could work. I was planning to use some 22AWG wire so that sounds doable, however I might use a slightly different solution suggested below.
MorganS:
Daisy chain = bad
Star = good
What is good for grounding is also good for power. If you have any analog puts then its essential.
I mentioned in my post that I would do this for the supply of power, not to connect control wires. Is that what you meant, or do you think that daisychaining power to a component that uses separate analog in/output would also be a bad idea? If it is the latter, is this because the analog puts would be more prone to disturbance from the input power when shared?
MarkT:
On a breadboard take the power and ground pins direct to the busbars along the edge of the
breadboard, but feel free to daisy chain from those pins per chip. And don't forget decoupling!
Thanks, I wouldn't be able to fit in an actual breadboard, as I mentioned space is tight, but I see what you're suggesting overall.
I think my solution given all these inputs would be something based on MarkT's suggestion, unless forum wisdom has it otherwise. I could use a small stripboard section (ie. 2 x 10) and connect Arduino +5v/GND through this, then share (i.e. daisychain) the 5v connection per component, but connect each component back to the "power strip". Sounds OK?
