Transferring data whilst keeping power source isolated

Hi,

I need to have an isolated power source for my Arduino Micro project. This is easy enough - 9V battery.

I also want to transfer data from the Arduino Micro to my PC in real-time as it is acquired. This is also easy enough, using serial commands.

However, as soon as I plug in the USB cable my project is technically no longer isolated. As it can be powered from the USB connection and therefore my PC.

How can I transfer data from my micro without powering it from the USB?

  • Can I stop the USB powering the board, but still transfer data?
  • Can I contact to board in an alternative (but still easy) manner to transfer data?

Thanks

What else is it connected to, which it needs to be isolated from? A battery-powered project with no other connections to electric power sources doesn't care if it's isolated or not.

You need an isolated USB lead. They are not cheap.

Use a wireless connection for the data, e.g. Bluetooth serial.

Thanks for the replies, by isolated usb cable do you mean something like this?

https://www.amazon.co.uk/HifimeDIY-Isolator-ADUM4160-signal-isolation/dp/B00M1QQBJ0

Bluetooth sounds like a good idea but I was hoping to use the existing usb connector for neatness and space issues.

by isolated usb cable do you mean something like this? ......

Yes. That is quite a cheap one, maybe because it can only supply 200mA.

As I don't want/need it to supply any power at all, are there solutions that do this? I.e. My arduino won't power up until my external power supply is connected?

I imagine with this isolated cable, it would still power-up the arduino, which isn't desirable.

Thanks

Use Midi. It is opto-isolated.

Dogberry:
USB connection and therefore my PC.

How can I transfer data from my micro without powering it from the USB?

  • Can I stop the USB powering the board, but still transfer data?
  • Can I contact to board in an alternative (but still easy) manner to transfer data?

Yeah.....use a bluetooth or wifi module to call home....ie arduino to computer wireless communications.

As for usb..... it is a system ....and 5V is part of that system requirement....for that comms method.

Just read up on this ...click here....

Another way might be i2c communications.

Do you want to keep the grounds isolated too? I think if you cut the red wire from the USB cable it will still allow data as long as the ground is connected. Im pretty sure i did this once and it worked fine.

Yep, grounds isolated as well, nice idea tho.

Thanks for replies, I'm going to try and find space for a bluetooth module and see how it goes.

Dogberry:

  • Can I stop the USB powering the board, but still transfer data?

Yes but you are not isolated at all - the data lines in USB (unlike ethernet) are connected to the
Arduino directly.

Hi,
Use a Laptop running on battery, the fact that the USB will be powering it is not a problem, its the gnd references that cause the problems.

UNLESS the potential that the arduino is operating at with respect to gnd is dangerously high.

Tom.... :slight_smile:

No typing on the keyboard at 10,000V!

Hello there,

There are a couple low cost options.

The first is to use RS232 instead. with this you can use a high speed opto coupler to isolate the arduino from the computer RS232 port, or use a USB to RS232 converter.

The second is to just use another arduino as the host. Your current arduino can communicate with the second arduino through RS232 with the opto, or just another single or double wire communication protocol, where each line is opto isolated. For example, one line is clock and one line is data, both opto coupler isolated.
The first arduino sends the data to the second through one or more opto couplers, and the second one sends it to the computer through whatever port you are using now like USB.