Physical construction: Shield, or..?

When I build a project, like the one in the circuit diagram below, the most challenging part is the physical construction. Lots of wires and connections:

I am using a Nano and will use a terminal screw shield. That part is OK. But then the rest: the logic level converter, the sensors and RTC: how and where to mount them? Any suggestions? How do you al do this? I am looking for a permanent construction, not something using breadboards or anything like that.

As always, any advice welcome. This forum has been awesome.

I've used a Mega with prototyping shield for such projects. Except you would use an Uno. I even socketed the modules by soldering female header strips to the proto shield.

Yeah, I was afraid of that: so much for my nanos! I guess the nano will be only for those apps that have only screw terminal inputs/outputs, then...

Yes, or installations where you can push female Dupont connectors directly on to the Nano pins. But that isn't really good for something permanent. I've also soldered Nanos and similar boards to a proto board, by the pins. Then it can be any solder proto board from an electronics supplier, doesn't have to be a shield.

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I want to add a note about the use of A4 and A5. You can't use them for both I2C and as analog inputs.

Oh, both those sensors are I2C, don't worry. The circuit works already, albeit in breadboard format...

Good! My mistake.

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No problem! In fact you raise a good point: the limited inputs/outputs available. I do not like using analog ports to drive LEDs, nor to read switch status, but I see little other option... as it is, only three ports left, and knowing how much I like switches and "blinkenlights", I'll probably find a use for those, too... :slight_smile:

On the Nano, there are two analog only pins, A6 and A7. If you use those for analog, the other analog pins are free for digital use.

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Why not ?

Well, let's call it cognitive dissonance: I am driving (or reading) something that is purely digital, 1 or 0, and doing that with an analog port seems wrong. I know it works, and I know that digitalRead handles the levels etc, but still, it feels sub-optimal.


digitalRead() doesn't "handle the levels". The processor configures the pin driver hardware to do either analog or digital. Once that is done, there is not a whit of difference between an analog pin configured for digital I/O, and a digital pin configured for I/O.

You can clarify such doubts by consulting the source code which is available online:
and reading the AVR data sheets.

What I mean is that it does not force ME to detect whether an input is high or low (>512 or <512): it does that for me.

But not sub-optimally.

Oh come on!

On the ATmegaxx8 they are clearly and unequivocally digital pins with the same functions as any other. You have a convenient option to use them as alternate inputs to a multiplexer which feeds a basic ADC.

Perhaps more importantly, you should generally reserve A4 and A5 for use as the I²C interface. A6 and A7 are reserved for exclusively analog use. If you need analog inputs, reserve as many of them for that use as you need.

If you do not need analog inputs then consider A0 to A3 as just four digital pins. :face_with_raised_eyebrow:

Yes, I know they work (see the schematic). It's just that anything not immediately clear can be confusing, like connecting something digital to a port called Analog. I know, of no functional consequence.

Yes, I am using the I2C pins. Only using A6 and A7 because otherwise, in the schematic you get even more crossed wires :slight_smile: I'll have to have more crossed wires I guess...

If use screw terminals or soldering point-to-point wires can be a hassle, do you design a PCB and place an order with a Chinese PCB manufacturer?
Includes all connections, reduce overall sizes and looks good.
Furthermore it basically costs under $10.
But basic PCB CAD skill required.

So now I need to learn PCB CAD skills. No problem. Any mints as to how I go about this - what software I use?

PCB CAD has multiple software options.
I have another post that links to some of the famous ones I think of, so I'll introduce them.

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And I should have added: I am Mac-based. That probably reduces the options.