Hi.
I'm building a water pressure sensor on ESP32 (MH-ET LIVE Development Board) ADS1115 (I2C) 2x DFRobot SEN0257 (cable to each sensor ~1m), and I want to take 64 measurements/s and send to Home Assistant (ESPHome) a value every 1 s, counting the median of the said 64 measurements.
Assumptions and components:
- SEN0257 powered from 5 V, analogue output 0.5-4.5 V goes to ADS1115 via divider: R1 = 2.2 kΩ (from signal), R2 = 5.1 kΩ (to GND), plus RC filter: C1 = 100 nF (ceramic capacitor, filter marked in orange in the picture) from measurement node to GND (capacitor as close as possible to AIN pin of ADS1115).
- ADS1115 supplied with 3.3 V from ESP32; on power supply at ADS1115 I give 100 nF (ceramic), 3.3 µF (tantalum) in parallel VDD-GND, following typical practice of decoupling close to power supply pins.
- at each SEN0257 (at the end of the 1 m cable) I plan 100 nF (ceramic), 3.3 µF (tantalum) between 5 V and GND, to stabilise the power supply on the long cable (marked green in the schematic).
Questions for verification:
1. Is the 2.2 kΩ / 5.1 kΩ divider well matched under the ADS1115 3.3 V (also in case of emergency, if 5 V would appear on the input)?
2. Does C1 = 100 nF make sense at 64 measurements/s, or is it better to give a different capacitance (I am concerned with the trade-off: electrical interference vs fast pressure spikes)?
3. Does the capacitor placement (bulk 'small' close to the circuits/sensors) and ground routing look OK, or should I change something?
Please check if my layout for pressure measurement is correct (I paste the schematic below).
Thank you for your help,
Viv
I'm building a water pressure sensor on ESP32 (MH-ET LIVE Development Board) ADS1115 (I2C) 2x DFRobot SEN0257 (cable to each sensor ~1m), and I want to take 64 measurements/s and send to Home Assistant (ESPHome) a value every 1 s, counting the median of the said 64 measurements.
Assumptions and components:
- SEN0257 powered from 5 V, analogue output 0.5-4.5 V goes to ADS1115 via divider: R1 = 2.2 kΩ (from signal), R2 = 5.1 kΩ (to GND), plus RC filter: C1 = 100 nF (ceramic capacitor, filter marked in orange in the picture) from measurement node to GND (capacitor as close as possible to AIN pin of ADS1115).
- ADS1115 supplied with 3.3 V from ESP32; on power supply at ADS1115 I give 100 nF (ceramic), 3.3 µF (tantalum) in parallel VDD-GND, following typical practice of decoupling close to power supply pins.
- at each SEN0257 (at the end of the 1 m cable) I plan 100 nF (ceramic), 3.3 µF (tantalum) between 5 V and GND, to stabilise the power supply on the long cable (marked green in the schematic).
Questions for verification:
1. Is the 2.2 kΩ / 5.1 kΩ divider well matched under the ADS1115 3.3 V (also in case of emergency, if 5 V would appear on the input)?
2. Does C1 = 100 nF make sense at 64 measurements/s, or is it better to give a different capacitance (I am concerned with the trade-off: electrical interference vs fast pressure spikes)?
3. Does the capacitor placement (bulk 'small' close to the circuits/sensors) and ground routing look OK, or should I change something?
Please check if my layout for pressure measurement is correct (I paste the schematic below).
Thank you for your help,
Viv
Do you have any advice on how to distribute the lines or other useful advice?
