I've seen these but I'm mildly confused on the connection to the sensor part.
It looked like the 9V-24V came from an external powersupply but the ground is connected to the Arduino. What is powering the arduino?
If it's a battery, where does the external powersupply's ground go? I don't see it connected to the sensor in this sample. I'm confused here, please help. Thanks!
Edit: To avoid confusion, this is not my schematic/system. I found this over the internet and confused where the ground connected from the external power source went on the sensor.
Ground is connected in this image. To both the sensor (whatever it is) and the GND pin on the Arduino, follow the line that curiously starts out red then changes black halfway through.
It also shows Arduino +5V to the sensor VCC, depending on what that is, watch that it's well within the limits of the Arduino +5V regulator.
That power supply of unknown origin has 9-24V there, connected to nothing. I guess that's a Giga Wifi board? 9-24V in to the board is within spec, but I wouldn't recommend inputting a much higher voltage than is needed, the 9 volts from a good power supply (ie not a smoke alarm type 9V battery) is enough. More is just heat you don't need through the regulator.
It's not what I was actually trying to ask here... But yes, it's an Uno board. I just wanna know where the ground connection from the external powersupply went cause I browsed some projects on YouTube and I saw the same with the Ground from the external power supply missing from the schematic. So I'm confused where it went.
Oh, I see now. The 9-24VDC here is IN for the soil sensor. @kariman02 gee thanks for the clarity the first time (sarcasm).
Based on that other page, that could work but I don't love the 2*3.7V power plant for the entire rig. I don't love voltage step ups either, I prefer to step down with a buck converter. Since fully charged, the battery here will be just over 13 volts so I would still use the buck converter dialed in to very slightly more than 9 volts.
For power I would use a 12V, 5Ah (alarm system battery back up, often) SLA battery and create two power rails, a +12V and a +5V using two different sections of terminal strip/terminal block and a ground lug to connect all the grounds together and back to - on the battery.
Ground is ground. Everything goes back to the negative terminal on the battery (eventually if not directly), even things like a metal chassis in certain applications.
For your project, a terminal block would suffice here, too. Just use bits of 14 AWG wire to jumper between the terminals in the strip/block.
Google terminal block or terminal grounding block if you don't know what I mean.
Do you have a multimeter and access to a car? Try this: Put the positive probe on the positive battery terminal in the car and the negative probe anywhere with unpainted metal. Compare to your measurement of just measuring the car battery terminals.
Even the metal chassis is strapped to ground which leads back to the battery.
The other page is almost entirely not connected to this question, that's why I separated the topic. This was a question asking where the ground from the external power supply went.
The other topic was about whether the system for the battery in the schematic would work with the step up converters.
Thanks for the answers though!
For more explanation on the other thread, I'm trying to go for the cheapest option. That's why I thought 2x 18650 batteries would work on powering a sensor and arduino for less than a minute at a time. Purely just to get a reading and then powering itself off.
If that wouldn't work with the current schematics, How do I improve the connection?
Can I try the current schematic first? I don't have all the components yet because it's still shipping. I'm just planning for everything so I won't get confused doing everything at once.
Ground is ground. Everything goes back to the negative terminal on the battery (eventually if not directly), even things like a metal chassis in certain applications.
For your project, a terminal block would suffice here, too. Just use bits of 14 AWG wire to jumper between the terminals in the strip/block.
Google terminal block or terminal grounding block if you don't know what I mean.
Sorry, I can't really imagine what you're saying here. Even if I google. I'm not well versed in these context.
Sure, try it. There's nothing in there that will damage anything. I would reconsider building a project around a breadboard though. That's not what breadboards are intended to be.
Thanks! Yeah, I figured... It's my first time building schematics and on the Uno board, I only see 1 5V output so I used a breadboard to simulate having two outputs of 5V, but irl, I would connect the TTL module to the other 5V on the upper side instead. Thanks for the heads up!
In general, and especially in DC Arduino projects like yours, all the wires that connect to anything that says GND or serves that purpose for some component, whether the Uno, the sensor, the module, whatever, all those GND connections connect together either through something like the GND on the Uno (all those ground pins are connected together internally) or literally to each other via the ground wires you used to hook it all up.
All those ground wires that are connected together all go back to the - terminal on the battery. There are lots of ways to physically do this.
I find the easiest way is to connect the ground wires all to a ground lug or terminal block. A ground lug can be a conductive nut or bolt if you like. Then take a length of wire, connect that lug to - on the battery.
Do not use the same approach with + voltages, just to be clear
I thought I understood everything you said until the thing with the ground lug and terminal block. I don't really understand how they work. Won't a wire that's connected to the battery's ground be enough?
Each circuit has a reference point to which all measurements and circuit descriptions are based.
This is usually termed "ground" and in the case of your project, that is the negative terminal of your power supply.
When ever you measure voltages in a circuit, unless stated otherwise, gnd is the reference point for all measurements.
When describing signal flow, ground is used a the reference point for the direction and magnitude of that signal.
In your project, all negative or ground connections got to the battery negative terminal as all signals will be referenced to this point.
It looks like I have to study and watch some stuff about the basics of electricity since I just can't understand clearly until I see a diagram or a simulation of some sorts on how things work 1 by 1.
I'm gonna try doing some research on this before my components arrive and hopefully I start to understand a thing or two.
Right now, all I understand is that all positive output that came from the battery will go back to its negative/ground terminal. and it's fine to connect all GND terminals together no matter the volts? together as long as it connects back to the battery's GND? Still a bit confused on that part.
