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1. Resolution: Higher resolution (at least 16-bit, preferably 24-bit) ADCs are usually required to capture the small variations in the analog output from a load cell.
2. Sampling Rate: Although load cells do not require very high sampling rates, a rate that can capture the necessary dynamic range is important. Common rates are around 10 to 80 samples per second, depending on the application.
3. Low Noise: Low noise performance is critical in capturing the minute signals from the load cell accurately without the noise overshadowing the signal.
4. Integrated Amplifier: Many load cell ADCs come with an integrated programmable gain amplifier (PGA) to amplify the small signals typically output by load cells.
5. Differential Input: Load cells typically output differential signals, so the ADC should support differential inputs.

1. HX711: A cost-effective 24-bit ADC with an integrated amplifier. It’s quite popular for its simplicity and ease of use with microcontrollers like Arduino and ESP32.
2. NAU7802: This 24-bit ADC from Nuvoton has differential inputs, low noise, and integrates a PGA, making it another good choice for precision measurements.
3. AD7190/AD7191: Analog Devices’ 24-bit ADCs with low noise and high resolution, capable of accurate load cell measurement.

• Resolution: 24-bit
• Integrated Amplifier: Included
• Differential Input: Supported
• Low Noise Performance: Designed for precision measurements.

• Power Connections:
  • Connect $U3: AVDD/LDO$ to 3.3V (PP3V3)
  • Connect $U3: DVDD$ to 3.3V (PP3V3)
  • Connect $U3: AVSS$ and $U3: DVSS$ to GND
• Load Cell Connection:
  • Connect the load cell positive output to $U3: VIN1P$
  • Connect the load cell negative output to $U3: VIN1N$
• I2C Communication:
  • Connect $U3: SCLK$ to I2C_SCL net
  • Connect $U3: SDIO$ to I2C_SDA net
• Other Important Connections:
  • Connect $U3: XIN$ to external clock source if using it, otherwise leave as per the datasheet recommendations.
  • Optionally, connect $U3: R-EFP$, $U3: R-EFN$, and $U3: VBG$ appropriately if these reference pins are used in your design.

ryanf

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1. HX711:
   • Resolution: 24-bit
   • Integrated Amplifier: Yes, with PGA
   • Differential Input: Yes
   • Average Cost: Very low
   • Applications: Widely used in weight scales and other load cell-based applications.
2. ADE7758:
   • Resolution: Up to 24-bit
   • Integrated Amplifier: Yes
   • Differential Input: Yes
   • Average Cost: Low
   • Applications: Energy monitoring, but also suitable for load cell measurement due to its high resolution and amplification capabilities.
3. ADS1232:
   • Resolution: 24-bit
   • Integrated Amplifier: Yes, with PGA up to 128x
   • Differential Input: Yes
   • Average Cost: Low to moderate
   • Applications: General-purpose high precision measurement, suitable for load cells.

• Low cost
• Adequate resolution and amplification for load cell applications
• Easy availability and widespread use in various similar projects.

1. Power Connections:
   • Connect VCC to 2.6V-5.5V power supply (e.g., 3.3V or 5V)
   • Connect GND to ground
2. Load Cell Connection:
   • Connect the load cell positive output to A+ or B+
   • Connect the load cell negative output to A- or B-
3. SPI Communication:
   • Connect PD_SCK to a GPIO pin on your microcontroller for clock signal
   • Connect DOUT to a GPIO pin on your microcontroller for data output
4. Other Important Connections:
   • Connect RATE pin if you need to adjust the data rate (high or low, typically 10Hz or 80Hz).

• Power:
  • Connect HX711:VCC to the 3.3V $(PP3V3)$ net
  • Connect HX711:GND to GND
• Load Cell:
  • Connect HX711:A+ to load cell positive output
  • Connect HX711:A- to load cell negative output
• Microcontroller Interface (ESP32):
  • Connect HX711:PD_SCK to ESP32 GPIO (e.g., GPIO18)
  • Connect HX711:DOUT to ESP32 GPIO (e.g., GPIO19)

ryanf

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1. Resolution: The ADC has a 12-bit resolution.
2. Input Range: The ADC input voltage range is 0 to 3.3V (same as the supply voltage).
3. Effective Number of Bits (ENOB): Usually around 10-11 bits due to noise and other factors.
4. Sampling Rate: The ADC can sample at up to $2Msps$, but the effective rate for most accurate measurements is lower.
5. ADC Channels: ESP32-S3 has up to 20 ADC channels.

• Maximum load cell differential output voltage = $66mV$ (assuming load cell sensitivity is $20mV/V$ at $3.3V$ excitation)
• Desired full-scale ADC input = $3.3V$

1. INA125: An instrumentation amplifier specifically designed for bridge-type sensor applications like load cells. It also includes a voltage reference that can be used to excite the load cell.
2. INA114: A general-purpose instrumentation amplifier with high precision and low noise.
3. AD620: Another general-purpose instrumentation amplifier suitable for precise measurements.

1. Power Connections:
   • Amplifier VCC to 3.3V (PP3V3)
   • Amplifier GND to GND
2. Load Cell Connection to Amplifier:
   • Connect load cell positive output to the amplifier's non-inverting input
   • Connect load cell negative output to the amplifier's inverting input
3. Amplifier Output to ESP32-S3 ADC:
   • Connect amplifier output to one of the ESP32-S3 ADC pins (e.g., ADC1_CHANNEL_0 or ADC2_CHANNEL_0)
4. Gain Setting:
   • Configure the amplifier gain using external resistors as specified in the amplifier's datasheet to achieve a gain of around 40-45.

Cpp
int adcPin = 34;  // Example ADC pin

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);  // Set ADC resolution to 12 bits
  analogSetAttenuation(ADC_0db);  // No attenuation (0 to 3.3V)
}

void loop() {
  int adcValue = analogRead(adcPin);
  float voltage = adcValue * (3.3 / 4095.0);  // Convert ADC value to voltage
  Serial.println("ADC Voltage: " + String(voltage) + "V");
  delay(1000);
}

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• Low-speed mode: typically around 20-30 mA
• High-speed mode: up to 100 mA or more
• Typical operation: around 50 mA

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1. Analog Supply Current (AVDD/LDO)
2. Digital Supply Current (DVDD)

• Operating IDD, Analog (AVDD)
• Operating IDD, Digital (DVDD)
• Standby Current

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• Gain ($G$) should be able to scale the small mV-level signals from the load cells (e.g., microvolt changes due to weight) to a range suitable for the ADC.

• Input impedance should be significantly higher (ideally $> 1 \text{G}\Omega$) compared to the output impedance of the load cell to avoid loading effects.

• CMRR should be at least 100 dB to ensure that the common-mode signals, which are noise or interference signals, are suppressed.

• Offset voltage should be as low as possible (microvolt range).

• Input-referred noise should be minimal, suitable for precision measurements.
• Typical values might include noise in the nanovolt range for low-frequency applications.

• Bandwidth must be higher than the maximum frequency component of the signal you need to measure. A bandwidth of at least a few kHz is often sufficient for many load cell applications.

• The amplifier should operate within the power rails provided by the ESP32-S3 system (which could be 3.3V or another regulated voltage).

• The output should be capable of swinging from 0V to the maximum ADC input voltage, typically 0 to 3.3V.

• Check whether the amplifier's output stage can drive the capacitive load at the ADC input.
• The output impedance of the amplifier should be low to avoid affecting the ADC's accuracy.

• Programmable gain from 1 to 1000
• CMRR of 100dB
• Low offset voltage (<25 μV)
• Low noise

• Load Cell to Instrumentation Amplifier: Connect the load cell differential output to the differential input of the instrumentation amplifier.
• Instrumentation Amplifier to ESP32-S3 ADC: Connect the output of the instrumentation amplifier to the ADC input of the ESP32-S3. Possible connections:
  • Connect INA333:OUT to ESP32-S3:ADC1_CHX (choose any available ADC channel)

ryanf

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1. INA333 from Texas Instruments
   • Gain: Programmable from 1 to 1000
   • CMRR: 100 dB
   • Offset Voltage: < 25 μV
   • Noise: 50 nV/√Hz at 1 kHz
   • Power Supply: 1.8V to 5.5V
   • Output Swing: Rail-to-rail
   • Package: SOIC-8
   • Price: Typically around $1-$2
2. AD8237BRMZ from Analog Devices
   • Gain: Programmable from 1 to 1000
   • CMRR: 100 dB
   • Offset Voltage: < 50 μV
   • Noise: 40 nV/√Hz at 1 kHz
   • Power Supply: 1.8V to 5.5V
   • Output Swing: Rail-to-rail
   • Package: MSOP-8
   • Price: Typically around $1-$2
3. MAX4198ESA+ from Maxim Integrated
   • Gain: Fixed gain options of 100 and 500 (choose specific variant)
   • CMRR: 120 dB
   • Offset Voltage: < 10 μV
   • Noise: 13 nV/√Hz at 1 kHz
   • Power Supply: 2.7V to 7.5V
   • Output Swing: Rail-to-rail
   • Package: SOIC-8
   • Price: Typically around $2-$3

• INA333 is a good choice if you need a versatile, low-cost, low-noise instrumentation amplifier.
• AD8237BRMZ offers similar performance to the INA333 but with a slightly different footprint.
• MAX4198ESA+ provides very low noise and can be a bit more expensive but is still within a low-cost range.