Currently, I'm building a project for automatic watering (never seen before, I know).
I want to use 1 or 2 MCUs (depending on how much I can control with one, I'm mainly working with ESP because of inbuilt WiFi & BT capabilities, but that might change later) and control 8 capacitive soil moisture sensors as well as 8 water pumps.
For sensing, I have built a solution that loops through the channels of a C4051BE analog multiplexer - which uses up my A0 and makes me think of either switching to an Arduino or working around the issue by using a separate MCU for actually controlling the water pumps.
My main problem is when it comes to moving from the breadboard to an actually soldered solution. How does one power so many devices (MCU + multiplexer + multiple sensors) at once? I'd like to re-use a wall plug on which I snapped off the USB for direct cable access. On my breadboard, I have a line of connected pins to which I can draw currency from. How do I solve this on a PCB?
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Or there are different kinds of terminal strips. I generally like this kind because they are plastic and they can easily be cut-down to the number of terminals you need with a hacksaw and the connections & screws are pretty-well protected against shorts.
Using more than one processor just because you want more I/O pins is a bad idea. It is a trap beginners fall into often. The solution is to always use one processor and there are various ways you can get more.
For example your analogue multiplexer at the moment only uses one level of multiplexing. It is quite OK to fit another multiplexer to each multiplexer input. So if you have an 8 input multiplexer, and fit an other to each input then you get 64 analogue inputs.
You can use any 5V power supply, though given you are working with a 3V3 system, it is best to choose components and a power supply that match that voltage.
In exactly the same way. You use a PCB track that is a long line and can power as many devices as you have current for. Or on strip board you have one or more strips carrying all the positive voltage.
Remember to connect the ground of an external power supply to the ground of the Arduino. Do not forget your decoupling capacitors on voltage distribution lines.
thank you for your answers. Homedepot doesn't seem to like german visitors (some kind of geoblocking going on there?), but I looked up the components and got the grasp. However, I don't really got an idea on how to connect one power source with multiple consumers on a solder board.
@Grumpy_Mike I think there was some misconception (sorry, english isn't my first language!) - with "breadboard" I meant the solderless ones which come with bus strips.
Anyway, thanks for the tip with the multi-level multiplexing, this might save me some complexity.
Edit: I found a picture of what might be a solution for my powering problem. The person apparently uses legs from a resistor to connect several solder points to form a kind of bus. Might this be a valid solution from your POV?
I have a few reels of tinned copper wire (various thicknesses but I mainly use 21SWG) that makes the strip as long as you want. Not restricted to the length of a resistor.
Also strip board (Vero board) is better than what you had which is called "perf" (perforated) board.
Here are some examples of building stuff on vero board (strip board). With schematic, physical layout diagram and photograph of the real thing. These are simple Piezoelectric sensors each one mounted in a small Pringles box to make a set of drums.
The copper strips on the back of the board are shown as dotted lines on the physical layout. Also any breaks in the copper strips would be shown, or indicated as in the comments.
Notice all the connections to ground are on the top strip, and then a wire link to the emitter of the BC237 transistor.
I ALWAYS manage to burn myself with HMG. I'm also not allowed scissors, and have to write with crayon.
Seriously, HMG works at the prototype level, but less so for LVP (low volume production) or when maintenance is factored in.
Screws and standoffs allow modules to be easily changed without soldering if everything is separable. Soldered connections are less so, especially if soldered at both ends. Long term maintenance requires seperable modules with connectors.
But again, HMG works for the prototype stage, it's cheap, fast, easy, flexible, and sufficient for many apps.
Never let perfection get in the way of good enuf!
Yes it was neither of these, it was for individuates to make there own at a hobby level. Anyway the main motivation for showing this in this thread was to illustrate construction using strip board.
Once you add trying to drill the metal bottom of a Pringles can, then you are in serious trouble mechanically, and the whole project becomes too complex and messy to ever be a practical proposition for home construction.
