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Is a I2C converter needed?

A bit of an amateur question, but do really need a I2C logic convertor when operating 3.3v sensors from a micro controller like an Arduino Uno? I was of the understanding that you didnt need a convertor to read the digital signal and assuming the sensor is connected to to the 3.3v power. What am I missing?

Yes, you will need a I2C converter. Otherwise, the sensor may be damaged.(The BR’s documentation has stated this.)
Adding two 10K resistors can solves this problem.

In addition, the temperature of the soldering iron in the welding cable will lead to poor consistency, We’ve done a few trials and we’ve solved that.
There is room for improvement in the Bar30 and we are trying.

Thanks for your response.

When I read the background to the Arduino Uno logic levels (link below) it implies that as long as a 3.3v sensor (such as the “Celsius”) is 5v tolerant then the 3.3v logic from the sensor is very similar to the 5.5v logic and hence no conversion is required. This is the background to my earlier question, if this is the case then why the need for a I2C logic convertor? Is the answer that you dont technically need a logic level convertor but it is safer to use one?


The Celsius sensor isn’t 5v tolerant. It’s designed to operate at or below 3.3v. If your Ardiuno Uno uses 5v logic then you’ll need a level shifter on the I2C SDA and SCL lines (in addition to the pull-up resistors that @troy recommended).

You can see in the datasheet for the TE IC used in the Celsius that is specifies SCL and SDA have a max of VDD which is specified as 3.6v max.

My 2 cents - instead of using a level shifter simply get a 3.3v Arduino board.

Thanks for your response. I agree on the 3.3v Arduino Board option. However, if i want to persist with the 5v board am i correct that if i use the BR level shifter this addresses both the logic and the the addition of the 10k resistors? Or do i need to add the resistors as well?

I haven’t used it, but a quick glance at the schematic shows it has 1k ohm pull-ups on SDA and SCL. I was a bit confused by the statement on the product page that the Celsius and Bar30 work best at 5v. I’m assuming that means 5v power supply (since they both have onboard 3.3v regulators) and not I2C logic voltage.