Electronics > Beginners
Do you have to tie grounds together to get an arduinos IO to works with other...
Beamin:
...other chips or devices?
Say you have an Arduino powered off USB and you have some logic chips or simple devices that have the ability to get logic level signals on a bread board running off batteries. Maybe you want the arduno to program the memory of a another chip, can't think of the name but DIP package comes to mind, very simple learning electronics level chips. This chip has a pin that goes high and low for 1000ns to write data to it and another for data. Can you just hook one of the Arduino digital out pins to the chips input pin then connect a second digital out to the data pin? Or does everything need a reference for what ground is, so connect the negative of the batteries to a gnd pin on the arduino?
dmills:
In general yes, there has to be a common path for the return current if this is to work.
You do sometimes find that it seems to sort of work without an obvious return path, but that is because leakage and stray capacitance is getting the job done for you, it should never be relied upon.
Currents flow in loops (always), make the loop the current flows in predictable and things may work well, make the loop something that happens by chance and things work less then well (or not at all).
Regards, Dan.
rstofer:
There are no one-wire circuits. To actually be a circuit, the path must go 'around'. The word circuit was well chosen:
https://en.wiktionary.org/wiki/circuit#Etymology
Zero999:
Yes, a common ground is needed. As mentioned above it might work without an obvious return path, but it could be unreliable and even cause damage, if the two circuits float at high voltages, relative to one another.
In some applications it might be necessary to maintain different grounds, which is why opto-couplers, pulse transformers and digital isolators are used. One of my favourites is the Si8642, which provides two channels in each direction, across an isolation barrier.
https://www.silabs.com/documents/public/data-sheets/si864x-datasheet.pdf
IDEngineer:
--- Quote from: rstofer on October 16, 2018, 02:20:05 pm ---There are no one-wire circuits.
--- End quote ---
WHAT?!? You mean Dallas Semi was lying to us all this time?!? :palm:
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