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How do I combine these circuits into one schematic? (for project purposes)

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Mar 7, 2022
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I started the basics of PCB and doing schematics around 6 weeks ago in my Computer Engineering Drafting and Design class. We used EasyEDA online tool to create the SCH and PCB for our assignments/activities. Our project now is to combine the circuits that we have made before into one system so that it has multiple features. The problem is (being all honest as I can), is that I lack understanding in fundamental electrical and electronic circuits since we did everything online and no actual hands-on.

So, about my task, I need help on how I could combine these circuits into one schematic so that I could simulate it properly, and convert it into PCB and 3D output. I will also need to simulate it in other tools/softwares such as TinkerCAD.

So attached below are those circuits that I made using EasyEDA, I just don't know how to properly connect them together... Do I change or modify the components themselves or change the values? I have no problem making the schematic and PCB. I just lack idea and understanding about the connections between components.

My plan is to turn my Battery Monitoring Circuit, Water Level Indicator Circuit, and Blinking LED circuit into one whole system.. As in connected together.

Also, they are simply needed to be connected together without errors (such as netlist, drc, etc.) and one thing, it doesn't need to be actually connected in a way that one circuit will respond to the other... Only simply connected as is. It's not like the water indicator responds to the battery monitor since I honestly can't find the point of connecting the two together besides this is given to us as a task. As long as the circuit is working, its fine.

Sources (the individual circuits aren't originally mine) :

Screenshot_20220305-174429_Canvas Student.jpg

I have to comment that those are not the cleverest of designs! With correction, the battery voltage monitor will work but you should really use comparators instead of op-amps and using them with no negative feedback is risking instability. At the very least you should add a capacitor of about 100nF directly across the VCC and GND pin of each IC.

Note that you have an extra line in your schematic from pin 3 of the top op-amp to VCC, it doesn't have a dot to indicate a connection but if you did join the lines you would short the batteries together.

I don't use EasyEDA but the normal way this would be done is simply to draw them all on one schematic then design the PCB accordingly. If you do not want any interaction between circuits, you have to use unique node names for the connections, for example if you use GND as a node name it will link them on the top two schematics so rename them a GND_1, GND_2 and so on. The same for VCC and any other shared names. Normally a PCB CAD program will assume all nodes with the same name are actually linked together.


Are you being asked to design one circuit that has all the functionality of the 3 separate circuits ?

Its hard to believe the intent is to learn how to cut and paste to show one page with all 3 circuits
on them......that thats the task for a EE student. As an aside all three circuits could be done with
a micro and a couple of resistors and a 3 terminal regulator and a couple of caps.

Regards, Dana.

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