I have attached a circuit sketch. I designed this circuit to allow one main power input for the various components. I can't seem to find a way to determine if this design could have low-voltage issues, or noise issues across the components. In general, I'm looking for those more knowledgeable of this type of power distribution to review this circuit to determine if there are any needs or issues that I could be missing.
Thank you!
Not real trouble but......
Feed the Mega from 5 volt into its 5 volt pin. Why waist power and create heating in the Vin to 5 volt converter of the Mega? Drop the 9 volt converter. Eventually replace it with a 5 volt converter. That will keep the Mega a bit more safe from eventual noise from the LED strip.
That will also eliminate any ground loop problem which might come up.
If you look at your current diagram, there is a ground from the mega and the 5v buck.
bluejets:
That will also eliminate any ground loop problem which might come up.
If you look at your current diagram, there is a ground from the mega and the 5v buck.
Yes. That ground cable is not needed as I can see..
That's weird way to wire the capacitor on you LED strip. 
Srsly, nice diagram. Looks plausible. I have done almost exactly this, but not using a high current motor. I would hope that the "shield" would, um, serve also as a shield against any motor issues.
How far apart are the 4 non-power blocks?
Use appropriate gauge wires.
Buck regulator specifications can be, er, optimistic, so save yourself some headache and be conservative on loading. Buy real ones, not eBay &c.
Test the regulators, don't ask me why I always run them on a dummy load at the expected current for the kind of times I'm making for.
a7
Railroader:
Yes. That ground cable is not needed as I can see..
Yes it is. What is the data going to reference?
alto777:
That's weird way to wire the capacitor on you LED strip.Likely a misclick when drawing...
Buck regulator specifications can be, er, optimistic, so save yourself some headache and be conservative on loading. Buy real ones, not eBay &c.
Test the regulators, don't ask me why I always run them on a dummy load at the expected current for the kind of times I'm making for.
Watching videos where people have made an autopsy on Chinese power devices it's clear to me that 1 Chinese Amp is equal to 0.5 Imperial, and Metric, Amp. In other words, calculate that You can get half of the Chinese specification.
- agree @RRer, just use 5 volts.
Thanks!
a7
SteveMann:
Yes it is. What is the data going to reference?
There is already a ground all the way from the top.
@RRer "Watching videos where people have made an autopsy on Chinese power devices it's clear to me that 1 Chinese Amp is equal to 0.5 Imperial, and Metric, Amp. In other words, calculate that You can get half of the Chinese specification."
You are an optimist!
a7
Eehh.. Even worse?
From what I can see, there are 2 ground loops. The ground from the Mega to the Stepper Motor Driver Shield and the wire labelled "Ground back to Arduino". If these were removed, everything will have a separate ground path back to the Power Bus terminals.
Railroader:
Feed the Mega from 5 volt into its 5 volt pin.
I could make this change, however, there is one other VL53L1X distance sensor not pictured in the circuit (sorry!) that will be connected to the 5V pin (plus ground, sda, scl) on the arduino. So, I though I would 'pad' the voltage by using the 12V - 9V regulator.
dlloyd:
From what I can see, there are 2 ground loops. The ground from the Mega to the Stepper Motor Driver Shield and the wire labelled "Ground back to Arduino". If these were removed, everything will have a separate ground path back to the Power Bus terminals.
I ran this by another formum on adafruit - I questioned this second ground from the LED back to the arduino. It was suggested on that forum due to the potential noise encountered back through the ground through 5V voltage regualtor. I would like to know if this second ground could cause an issue over what it is purported to solve.
Railroader:
Buck regulator specifications can be, er, optimistic, so save yourself some headache and be conservative on loading. Buy real ones, not eBay &c.
I believe each of three regulators provide 2x the amps anything could draw — thanks for this reminder, I will be sure to check current draw and voltage coming from these regulators. They weren't the cheapest regulators available on Amazon, but they're definitely on the low-end.
alto777:
I would hope that the "shield" would, um, serve also as a shield against any motor issues.
Yep, it has protections built right into the shield.
alto777:
How far apart are the 4 non-power blocks?
Use appropriate gauge wires.
All of these components (minus motor and lights) are secured to an ~8 in square panel so the power lines are all less than 10". I probably use higher gauge wires than needed, perhaps I should pay more attention to the resistance in my wires/connections — how can that effect things if you may know?
alto777:
That's weird way to wire the capacitor on you LED strip.
Ha, I, errr, was going from icon-memory when drawing this 
Oh, so you may have something like this for the 5V converter and the stepper driver is a shield that might connect directly to your Arduino, so you may have little control of how the grounds are routed (and length and wire size). I would suggest that instead of adding the "Ground back to Arduino" wire, add a "Ground back to Power Bus Ground" from the LED Strip.
dlloyd:
...suggest that instead of adding the "Ground back to Arduino" wire, add a "Ground back to Power Bus Ground" from the LED Strip.
Unless I'm not understanding correctly, there is a ground from the LED strip back to the 5V regulator... it isn't labeled, but the red and black lines going to the LED strip represent the 5V and ground. So, in my diagram I actually have two grounds right now. I'm going test removing the "Ground back to Arduino" and watch for noise or signal disruptions going to the LEDs.
Yep, the adafruit motor shield connects directly to the arduino and is built to accept 5-12V power specifically for the motor - though a jumper can be used to draw power from the arduino VIN, but I rather not do that.
I meant something like this (if you're concerned with existing wire size and length and grounding through the 5V buck regulator) ...
That diagram indicates a ridiculous open loop in the data line to the LED strip. That is what you really need to avoid.
Firstly, the two down converters need to be co-located so there is virtually no length to the ground wires between, nor any significant distance between them and the Mega (itself a rather inconvenient form factor but presumably practical if using a "shield"). So you run the data wire back from the beginning of the LED strip along with the 5 V and ground - that is in a single bundle - to the 5 V regulator where it then runs across to the Mega the short distance again along with the 5 V and ground which power the Mega via the "5V" pin.
You see, the Mega actually operates at 5 V, so 5 V is what you should use to supply it. Using the on-board regulator is just asking for trouble. There is a concern - of "back-powering" the USB port - if you supply 5 V to the "5V" pin when it is connected to a PC by the USB port so you need to disconnect only the "5V" pin while connected to the PC. This is not a problem if powering from "Vin" or the "barrel jack", or when using a Nano or Pro Mini.
The general concern is that at each point, supply and ground or signal and ground or all three connections should always run together as a bundle to avoid any open loops in the wiring.
I've never heard of star-point grounding being ridiculous. The additional ground wire to the power junction should actually improve grounding. However, I haven't used these LED strips before, so I'll bow out.
Using a point as near the powersupply as possible as the grounding point gas served me well. Let's call that point the center if the star.
Paul__B:
Firstly, the two down converters need to be co-located so there is virtually no length to the ground wires between, nor any significant distance between them and the Mega (itself a rather inconvenient form factor but presumably practical if using a "shield"). So you run the data wire back from the beginning of the LED strip along with the 5 V and ground - that is in a single bundle - to the 5 V regulator where it then runs across to the Mega the short distance again along with the 5 V and ground which power the Mega via the "5V" pin.You see, the Mega actually operates at 5 V, so 5 V is what you should use to supply it. Using the on-board regulator is just asking for trouble. There is a concern - of "back-powering" the USB port - if you supply 5 V to the "5V" pin when it is connected to a PC by the USB port so you need to disconnect only the "5V" pin while connected to the PC. This is not a problem if powering from "Vin" or the "barrel jack", or when using a Nano or Pro Mini.
The general concern is that at each point, supply and ground or signal and ground or all three connections should always run together as a bundle to avoid any open loops in the wiring.
I see — I do like the idea of remove some parts from this chain. However, I omitted one key component from the circuit diagram (sorry). I have a VL53L1X ToF sensor connected to the Mega directly (5V, Gnd, SDA, SCL) but I it can run at 3.3V after looking at the data sheet (max 18mA).
I don't know enough about power to determine if this affects your idea of simply running the Mega off the 5V regulator?
The power bus, Mega and voltage regulators are all mounted within inches of each other with sub 10 inch lines. The motor, LED strip, and ToF sensor may up use to 15" lines. It will all be very compact.
You see, the Mega actually operates at 5 V, so 5 V is what you should use to supply it. Using the on-board regulator is just asking for trouble. There is a concern - of "back-powering" the USB port - if you supply 5 V to the "5V" pin when it is connected to a PC by the USB port so you need to disconnect only the "5V" pin while connected to the PC. This is not a problem if powering from "Vin" or the "barrel jack", or when using a Nano or Pro Mini.
The general concern is that at each point, supply and ground or signal and ground or all three connections should always run together as a bundle to avoid any open loops in the wiring.
Thank you for this concise explanation!
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