Bar30 Extension cable

Blue Robotics Products Sensors
1

Hello!

I was wondering, since i can’t find any specific details in the technical file, if there is a possibility to extend the cable for the bar30/bar10 product. Can someone help me figure out the maximum range?

My plan was to have the Arduino Uno on the surface and the bar30/bar10 below surface, hence the question

Thank you in advance!

2

Hi @Moke3, welcome to the forum :slight_smile:

The I2C protocol is not designed for long cables, so we generally wouldn’t recommend this. That said, there are ways to extend the maximum usable range if necessary, including

  • reducing/isolating nearby electrical noise sources, and using a shielded cable
  • carefully managing the cable impedance
  • running at a low clock speed
  • using an I2C bus extender

The specific maximum range is application-dependent.

3

Hello Eliot, thank you for the welcome and thank you for the answer.

Since i’m quite new at this, but i have some experience with cable harnesses, though not with a signal such as this.

Basically the application involves the Bar30 sensor with the Arduino only, basically uninterupted by any EMC (I can place the batteries somewhere else a bit away). I have access to shielded 1.5mm^2 copper cable and i could add an I2C bus extender if required.
Do you think this could reach down to a approx. 10 meters below surface? I have significantly less knowledge in signal loss than i’d like to admit.

4

Hi @Moke3,

Apologies for the slow response on this.

I don’t have much experience with attempting long I2C cable lengths, but from your description my intuition is that that should work ok, especially if you keep to a low-ish communication clock speed.

5

Hi friends!
I’d be shocked if you’re able to get an unmodified I2C signal to travel that far. The protocol was designed to be used on circuit boards, and not for significant distances. The common rule of thumb for most I2C connections is 1 meter or less, but it may be possible to do farther, if you have very little noise / interference.
"For reference, shielded 22 AWG twisted pair cables have capacitance in the range of 100-240 pF/m. So the maximum bus length of an I2C link is about 1 meter at 100 Kbaud, or 10 meters at 10 Kbaud. Unshielded cable typically has much less capacitance, but should only be used within an otherwise shielded enclosure.
"

Your best bet would be a bus extender that converts the signal to differential, rather than the typical protocol. That linked product claims 100 feet, but I’ve never attempted it with a Bar30 or Celsius - please let us know how it gos if you try!