groundinterconnectmainspower supply
I'm having the following circuit:
Where TWL6030 is a DC-DC buck converter and INA219 is a high side current sensing circuit.
My problem is with the power sources,Vbat and Vs are two different (no common ground) power supplies and Vs is a cheap noisy power source.
Is there a problem of having the common ground between INA219 and TWL6030?
Is the noise of Vs going to influence the functioning of the buck converter?
You need a point where the two power supplies connect, and most of the time this is the ground of both supplies. If you don't connect them they will "float" with respect to each other, meaning that the ground (or any other level) of the second supply doesn't have a defined level with respect to the first.
If they're not connected by a common ground no current will flow from the output of one circuit to the input of the second, since there will be no closed loop where the current can flow back.
how does it know to go back to the battery and not the ground on the Arduino chip
The most negative point on the system is where the current heads for just like a plug hole in a bath - this is where the water wants to go because of gravity. If there's a ridge in the tub (equivalent to one amongst several ground wires having slightly higher resistance), the water (or current) will tend to go round it to find the lowest point.
Your wiring schematic should also look like this so that there is no chance current taken by the motors are drawn along digital ground wires. It's called star-pointing: -
Best Answer
No problem on both counts. But:
a) You'll get more answers if you draw schematics that are easier to review by following common conventions: Rules and guidelines for drawing good schematics ... notably, general flow of action from left to right.
b) The noisy VS could well affect the INA219. So if the measurements are worth taking, it would be worth fixing that so that it's protected from going outside the allowed Vs range and it's reasonably smooth... this should only take a capacitor or two, perhaps a regulator, depending on the problem.
c) If by "noisy power source" you actually mean a power source with a noisy ground, then you may have more to think about, both with respect to contributing noise to whatever's downstream from the TWL6030, and also to the computer connected to the I2C interface (which will also share a ground with this apparatus).
Hope that helps.