Possibility to leave the USB 5v and Gnd unconnected and still pairing to a comp?

For a project I am working on space matters a lot. So I took the USB connector off my UNO and use 2.54 pins to connect a usb cable on the underside of the UNO, which works a charm.

I found a way of feeding the arduino through the 12V line connected through the Vin port, was wondering if I could leave the 5V and GND in the USB unconnected and only using the D+ and D- lines whilst being able to connect to to the serial monitor? If I leave the 5V and GND lines out the computer won't see the connection.

I tried doing it but I can't get it to work, it would save me a lot of wiring. To my understanding connecting both to vin and the USB at the same time is not recommended.

Any help or suggestions would be appreciated, even a simple "this will never happen" would save me time :slight_smile:

Please explain why you don't use the USB connector with an USB cable, or why you don't use an USB cable for connecting the Arduino to a PC USB port.

I you don't use the certified cables and connectors, the results depend on your skills and understanding of EMF and high speed serial transmission.

DrDiettrich:
Please explain why you don't use the USB connector with an USB cable, or why you don't use an USB cable for connecting the Arduino to a PC USB port.

I you don't use the certified cables and connectors, the results depend on your skills and understanding of EMF and high speed serial transmission.

Don't have the space, simply put. No space to either side just on the bottom.

And for the time being this is more about feasibility. I understand that it might cause problems and blowing up a arduino or two is not all that important to me, using a few in the project and need to coordinate through serial communications. Just wondering if I can lower the amount of cables to limit points of failure and stress on my part!

Dirkhens:
For a project I am working on space matters a lot. So I took the USB connector off my UNO and use 2.54 pins to connect a usb cable on the underside of the UNO, which works a charm.

So dump the UNO and use a Pro Mini, huge space savings.

Whilst you may understand what you mean by ‘2.54 pins’ a lot of people might be puzzled as to why you are cutting pins up so that you have 2.54 of them.

srnet:
So dump the UNO and use a Pro Mini, huge space savings.

Whilst you may understand what you mean by '2.54 pins' a lot of people might be puzzled as to why you are cutting pins up so that you have 2.54 of them.

Hehe, yeah 4 2.54mm pins instead of the standard of the USB connector, and not something most should be doing, I don't like doing it, but well like I said space.

And mostly went uno because the shield that is required for the time being is made for a uno. And doing it this way saves time. Resoldering all the wires from a smaller model though feasible mean it's less secure. A larger point of possible failure.

In essence let's just say that right now I want to cut down on wires, can I get around not using those two?

Dirkhens:
And mostly went uno because the shield that is required for the time being is made for a uno.

Ah, you did not mention before that you were using a 'shield' with the UNO.

You will get the best and most helpful answers to your questions if you provide a description of the project and the hardware you are actually using.

srnet:
Ah, you did not mention before that you were using a 'shield' with the UNO.

You will get the best and most helpful answers to your questions if you provide a description of the project and the hardware you are actually using.

Sorry you are right, the shield is a motor driver using a independent power supply. The project boils down to a motor arm with a large degree of freedom and hopefully scalability. This makes those two wires I could be saving a huge winning in end if I could use a multi-core with just the D+ and D- running up to the arduino's.

I was hoping to know if that was feasible or I should give up trying.

The computer won't care if the USB is drawing power over the 5V line. There's no data on that wire.

It definitely will care if GND isn't connected. There may be another ground elsewhere but it's vital for signal grounds to follow the signal wires with the USB data.

What happened when you tried it?

I think the Leonardo is the same size and shape as an UNO but it uses the micro USB connector. You could probably find an off-brand UNO which does, since those full-size USB-B cables were obsolete a long time ago.

MorganS:
The computer won't care if the USB is drawing power over the 5V line. There's no data on that wire.

It definitely will care if GND isn't connected. There may be another ground elsewhere but it's vital for signal grounds to follow the signal wires with the USB data.

What happened when you tried it?

I think the Leonardo is the same size and shape as an UNO but it uses the micro USB connector. You could probably find an off-brand UNO which does, since those full-size USB-B cables were obsolete a long time ago.

Thanks for the reply! I got it to reply when I hooked up the D+ and D- lines along with a power line from the same computer but it won't react to the D+ and D- when hooked up from external power. And using any other standard sized would leave me with the same problem. I have the space on the bottom but not on the sides.

Creating a common between the GND of the shield and arduino sounds iffy to me, should I try it or would you advise against it?

It sees it, just doesn’t work with it atm! Thanks so much! a step forward I very much needed.

Fixed it! Thanks! My D- Was flimsy, using a bad cable I took home for testing. In theory running a common wire would work and would need only only more wire and save me 5+! woohoo!

[Solved]

It will work when you disconnect the 5v, leave the ground there. You can use one cable for that. Feel so dumb atm...

Will using one cable for the common effect sensor input? I'm talking 3+ arduino's in link here. Can test it myself but if any of you know! You guys are a blessing from the gods.

Dirkhens:
Will using one cable for the common effect sensor input? I'm talking 3+ arduino's in link here. Can test it myself but if any of you know! You guys are a blessing from the gods.

daisy chaining 3 Unos together wont work. The problem is the monitor will not know which Uno is supplying which bits of data, and if 2 are transmitting at the exact same time but one is a 0 and the other is a 1 the computer will only see the 1. Going through a hub will allow simultaneous data transmission. The other way to make this work is to have one Uno set as a master (with the sketch) and the other 2 as slaves. The data would be through the I2C bus into the master and out the USB to the serial monitor. I don't know how to write the code for this but I have seen it done.