I bought this so that using a a bread board I can connect an Arduino Pro mini outputting 5V to a temperature and humidity sensor that is powered by 3.3V (https://www.sparkfun.com/products/13763). However, once I have everything hooked up, using a Volt Meter I can see that I am getting 5V out of the Arduino Pro Mini and 5V is reaching the level converter, but once I test the low voltage side of the converter I am getting nowhere near the 3.3 V needed. I am getting a millivolt reading. I tried 3 different units of the converter that I purchased, all of them with the same exact issue. Does anyone have any suggestions or ideas on what I am doing wrong?
If for some reason you’re inputting logic lows into one side of the converter, you should be seeing close to zero volts on the output.
Are you trying to use the level converter to power your sensor, or are you only using it for the SDA and SCL lines?
Do you have both 5 volt and 3.3 volt power connected to the logic level converter? If you can send a photo showing how things are connected, that would help us figure out what might be going on.
I am returning nearly zero voltage on the low voltage side of the converter.
I am trying to use the converter to power the sensor as well as use the SDA and SCL lines
Yes, I have both the 5 Volt and 3.3 Volt power connected to the level converter. I attached detailed photos to the post, hopefully the pictures make it clear what is going on. If you need any additional information please let me know.
OK, I’m not seeing where you have power connected to the low voltage side and the high voltage side power looks like it’s connected to A0 and A2. How are you supplying power via those pins?
What is the low voltage side connected too? Can you send photos and a wiring diagram showing all the connections?
Sorry, I forgot to picture what the low voltage side is connected to, I will attach them to this reply.
I am supplying power to the Arduino board via USB using a multi meter I was able to verify that Yes, I am getting the 5 volts from those two pins on the Arduino itself.
The low voltage side is connected to the temperature sensor.
I was trying to model my wiring similar to the diagram that is provided by SparkFun for the temperature sensor.
You’re not actually supplying power to the low voltage side of the level converter or the Si7021. You need to connect a 3.3 volt power source to the GND and LV pins on the level converter for it to work. Sadly, it can not work on 5 volts alone. You might have a look at our [hookup guide for ideas on how to connect power to the logic level converter.
Also, there is a trick with I2C if you only have this one device to connect to your Arduino. As long as you’re powering the Si7021 with 3.3 volts and you have no other 5 volt I2C devices on your I2C bus, you can get away with not using the level converter.
The reason that works is the Si7021 pulls the SDA and SCL lines high to 3.3 volts through some onboard pullup resistors. Normally both lines idle high at 3.3 volts and the Arduino only pulls SDA and SCL low so the Si7021 won’t ever see 5 volts from the Arduino. You MUST power the sensor with 3.3 volts though, 5 volts will kill it.
Ah that makes sense. Thank you for your help. I have it set up and working now.
I guess I misunderstood the purpose of the level converter. I thought I would be able to take a 5V power supply and convert that input voltage to 3.3V output to power my sensor.
My intention was to only use one power supply, I do have other 5 volt devices connected to the Arduino that I am trying to power as well with the sensor.
I was hoping that only one power supply would be necessary. Is there any product that you suggest that I could use make this possible?
