Gas Sampling Pump PCB Design

flux

I created the V1 pump design package without overwriting the existing NH3 loop-transmitter schematic.
Open items:
  • The current project already contains a complete analog NH3 4–20 mA transmitter, so I did not replace the schematic/layout.
  • To build the full pump schematic and PCB, I need confirmation whether to overwrite this project or create/fork a separate pump project.
  • Exact pump model/stall current and target board dimensions are still assumptions.
Suggested next steps:
  1. Confirm: replace this project or create a separate pump project.
  2. Provide the pump datasheet/model if you have one.
  3. Then I can capture the full schematic, run ERC, create layout/routing, and generate the final BOM/firmware/bring-up docs.
M

mikaelle

Yes, create a separate pump project and start the full schematic there.

flux

I’ll create a separate pump project, then start schematic capture there so the existing NH3 transmitter stays intact.

flux

The new project is created: /mikaelle/gas-sampling-pump-pcb-design. I’ve started a dedicated schematic-capture thread there and will wait for its result before continuing verification/layout.

flux

Created the separate project and started schematic capture there: /mikaelle/gas-sampling-pump-pcb-design
Open items:
  • The schematic-capture thread is still running in the new project.
  • Layout/routing will wait until schematic/ERC is complete.
Suggested next steps:
  1. Open the new project to watch progress.
  2. Once schematic capture completes, ask me to review/fix ERC and continue to PCB layout.
Review then layout
Check schematic status
Run ERC fixes
Explain pump protection
Optimize for manufacturing
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Schematic

Layout

Preview

Gas Sampling Pump V1 — Project Specification
Project Overview
Compact industrial external gas sampling pump PCB for portable gas detectors. Version 1 prioritizes simplicity, reliability, manufacturability, and stable open-loop flow near 400 mL/min rather than closed-loop flow regulation.
Intended Use
Standalone battery-powered pump module that draws gas through flexible tubing and pushes it toward a portable detector inlet. Intended for prototype validation of pump control, blockage/fault detection, battery operation, and manufacturable PCB integration.
Main Requirements
  • Single rechargeable 18650 Li-Ion cell, 3.7 V nominal.
  • USB-C 5 V charging.
  • Battery protection: overcharge, overdischarge, short-circuit, overcurrent.
  • Battery voltage monitoring and low-battery indication.
  • Low-noise miniature diaphragm pump, target flow approximately 400 mL/min.
  • MOSFET PWM pump drive with soft-start, startup current limiting by firmware PWM ramp, and stall detection by current/voltage behavior.
  • MCU: STM32G0-family preferred for low power, ADC, PWM, I2C, GPIO, and SWD.
  • Differential pressure sensor for blockage/disconnection detection only; no V1 closed-loop flow regulation.
  • LEDs: Power, Charging, Pump Running, Fault.
  • USB-C ESD protection, EMI filtering, reverse-polarity/current protection, power filtering, debug test points, robust grounding.
Selected Architecture
Diagram



  
    
  
  
    
  
























USB-C node_5V
USB ESD + EMI
BQ24074 Li-Ion charger / power path
Protected 18650 cell
System rail
3.3V low-Iq LDO
STM32G0 MCU
SDP33 differential pressure sensor
MOSFET pump PWM drive
Mini diaphragm pump
Status LEDs
SWD debug/test pads

Table

FunctionRecommended PartReason
Charger / power pathTI BQ24074RGTTUSB-friendly 1S Li-Ion charger with dynamic power path, 1.5 A class, compact VQFN.
Battery protectionDW01A + dual protection MOSFETCommon 1S overcharge/overdischarge/overcurrent/short-circuit protection approach.
MCUSTM32G0B1Kx LQFP32Low-power Cortex-M0+, ADC, PWM timers, I2C, GPIO, SWD, manufacturable package.
Pressure sensorSensirion SDP33-1500Pa3.3 V I2C differential pressure sensor suitable for blockage/disconnect detection.
Pump switchIRLML2502 or stronger low-Rds(on) logic MOSFETSimple low-side PWM switching from 3.3 V GPIO.
Pump connector2-pin JST/locking headerServiceable pump connection.
Battery connector/holder18650 holder or 2-pin battery connectorPrototype-friendly battery integration.
Power Budget and Runtime Estimate
Assumptions for V1 prototype:
  • Pump: 3.7 V miniature diaphragm pump, approximately 350 mA typical at 400 mL/min, 800 mA startup/stall transient.
  • MCU + pressure sensor + LEDs: approximately 25–45 mA active depending LED currents.
  • Average active current: approximately 390–430 mA.
  • 18650 capacity: 2600 mAh nominal, derated usable capacity 80–85% for protection cutoff, aging, and load effects.
  • Estimated runtime: about 5.0–5.6 hours continuous pumping; lower if pump current is higher or LEDs are driven brightly.
Firmware Behavior
  • On power-up: initialize GPIO, ADC, timer PWM, I2C pressure sensor, LEDs, and watchdog.
  • Soft-start: ramp PWM from 0% to target duty over 1–3 seconds.
  • Startup current limiting: monitor pump current or supply droop during ramp; hold/reduce PWM if threshold exceeded.
  • Stall detection: detect abnormal current rise, no pressure response, or severe supply sag.
  • Fault detection:
    • Blocked inlet: high negative differential pressure relative to baseline.
    • Blocked outlet: high positive differential pressure relative to baseline.
    • Disconnected tubing: unexpectedly low differential pressure while pump PWM is active.
    • Pump failure: PWM active but no current/pressure response.
    • Low battery: battery ADC below warning/shutdown thresholds.
  • LEDs: Power steady, Charging from charger STAT, Pump Running from MCU, Fault latched/blink code from MCU.
PCB/Layout Expectations
  • Suggested compact 2-layer PCB for V1 if routing is simple; 4-layer preferred for EMI robustness and ground integrity.
  • Keep USB-C/charger near board edge; keep high-current pump loop compact and away from pressure sensor/MCU analog traces.
  • Use a solid ground plane, star/controlled return strategy for pump current, and separate quiet 3.3 V filtering for MCU/sensor.
  • Place flyback/TVS/snubber close to pump connector and MOSFET drain path.
  • Add test points for VBAT, VSYS, 3V3, GND, SWDIO, SWCLK, NRST, I2C SDA/SCL, PUMP_PWM, PUMP_SENSE, CHG_STAT, and FAULT.
V2 Closed-Loop Flow Recommendations
  • Add a true mass-flow sensor or calibrated differential pressure across a defined flow restrictor/orifice.
  • Store flow calibration coefficients in MCU flash per pump/tubing assembly.
  • Add temperature compensation and barometric correction if measurement accuracy matters.
  • Implement PID or feed-forward + PI pump speed control.
  • Add filter lifetime tracking and flow calibration routine.
Assumptions / Open Items
  • Exact pump model and stall current are not specified; MOSFET, protection thresholds, and runtime must be revised when the pump datasheet is selected.
  • Exact board dimensions and enclosure constraints are not specified.
  • 400 mL/min stability target is interpreted as open-loop PWM repeatability in V1, not metrology-grade flow accuracy.

  • Project Overview

  • Intended Use

  • Main Requirements

  • Selected Architecture

  • Recommended Core Parts

  • Power Budget and Runtime Estimate

  • Firmware Behavior

  • PCB/Layout Expectations

  • V2 Closed-Loop Flow Recommendations

  • Assumptions / Open Items