Using a pressure sensor in combination with ESP D1 mini /ads1115/level converter

Hardware
1

I’m setting up my first esp home project with a pressure sensor and esp d1 mini.

The pressure sensor is a 100psi 0-4,5volt sensor with a vdd of 5V. As I want to use the full range of the sensor and want to have a good accuracy I choose to use a ads1115 and instead of a voltage divider a logic level converter board. I connected everything according to the scheme below.

But instead of changing the voltage the level converter is only topping of the voltage at 3.3. This means it start with 0,5V (0 psi) and goes to 3,3volt ( ~60PSI) and every above stays at 3.3 volt.
I would expect that 100 psi would be ~3volt and the whole scale should change. As this is my first project I’m probably making a rookie mistake while thinking. Does anyone now how I should connect the level converter board?

according this post: Building an ESP8266 with multiple pressure sensors (using ADS1115 and ESPHome) - #2 by tom_l

IT should be possible to set the logic level converter between the ads1115 and esp d1, however if I do that (between the scl en sda pins), the d1 won’t boot.

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Power your ADS1115 and pressure sensor from 5V.

Connect the pressure sensor output directly to the ADS1115 (A0 input).

Connect the level converter on the I2C lines from the ADS1115 (SDA and SCL) to convert them from 5V logic to 3.3V logic that the D1 Mini can handle.

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2 Likes
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Thanks, that setup did the trick!

4

curious, why is a 3.3V connection needed from the level converter to the ESP D1 (LV to 3.3)? good setup by the way - I’m in the middle of building this setup.

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My experience says that this setup does not work. I tried this without success, in case any component is faulty, I replaced all the components - some up to five times, each time the result was

[20:05:30][C][i2c.arduino:062]:   Recovery: failed, SCL is held low on the bus
[20:05:30][I][i2c.arduino:069]: Results from i2c bus scan:
[20:05:30][I][i2c.arduino:071]: Found no i2c devices!
[20:05:30][C][ads1115:073]: Setting up ADS1115...
[20:05:30][C][ads1115:074]:   Address: 0x48
[20:05:30][E][ads1115:076]: Communication with ADS1115 failed!
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Then you have likely connected something incorrectly as it worked for avd88.

EDIT: and Lary.

7

Sorry, missed this question. The 3.3v supply is used to generate the logic 1 level for the low voltage side of the level converter.

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8

Your post worked perfectly. Thanks!

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worked for me very fine as well!

thanks for the smart wiring-instructions to @tom_l - defining the logic 1 level for the low voltage side of the level-converter is the caveat. now that you mentioned it’s so obvious why all of my former approaches had to fail. thanks for the lesson :pray: