Gas Sampling Pump PCB Design
Yes, create a separate pump project and start the full schematic there.
Thought for 3 sec
I’ll create a separate pump project, then start schematic capture there so the existing NH3 transmitter stays intact.
Worked for 39 sec
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.
Worked for 4 mins 51 sec
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:
- Open the new project to watch progress.
- 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
Refine this doc
Ask about this doc
Gas Sampling Pump V1 — Implementation Plan
Recommended Schematic Blocks
- USB-C input: USB-C receptacle, 5.1 kΩ CC pull-downs, VBUS TVS/ESD, input fuse/current limiting, EMI bead.
- Charger/power path: BQ24074 with input/output/battery capacitors, charge-current resistor, input-current programming, STAT output to charge LED and MCU input.
- Battery protection: protected 18650 pack preferred for fastest V1; if protection is on PCB use DW01A + dual MOSFET protector and verify trip thresholds against pump startup current.
- 3.3 V rail: low-Iq LDO from system/battery rail, bulk and local decoupling.
- MCU: STM32G0B1K LQFP32 with SWD pads, reset pull-up/button, boot option, decoupling, ADC battery divider, ADC pump-current sense, PWM output, I2C bus, LED GPIOs.
- Pump driver: low-side logic MOSFET, gate resistor, gate pulldown, current sense resistor or high-side current monitor, flyback/TVS/snubber across pump/connector, bulk capacitance near pump supply.
- Pressure sensor: SDP33-1500Pa on 3.3 V I2C with pull-ups, decoupling, and tubing port orientation noted in silkscreen.
- User interface: Power LED, Charging LED, Pump Running LED, Fault LED, optional power/pump button.
- Test/debug: SWD, UART optional, rail and signal test points.
Candidate BOM
Table
| Ref Group | Qty | Candidate | Notes |
|---|---|---|---|
| J_USB | 1 | USB-C 16/24-pin receptacle | USB 2.0 power-only is sufficient. |
| U_CHG | 1 | BQ24074RGTT | Charger/power path. |
| U_PROT | 1 | DW01A | Only if using unprotected cell. |
| Q_PROT | 1 | Dual N-MOS battery protection FET | Select for pump startup current margin. |
| U_MCU | 1 | STM32G0B1Kx LQFP32 | Preferred V1 controller. |
| U_LDO | 1 | 3.3 V low-Iq LDO, >=150 mA | Select final part during schematic capture. |
| U_PRESS | 1 | SDP33-1500Pa | I2C differential pressure sensor. |
| Q_PUMP | 1 | IRLML2502 or stronger | Verify against real pump stall current. |
| R_SENSE | 1 | 0.05–0.1 Ω current sense | Size for stall power pulse. |
| LEDs | 4 | Green/amber/blue/red LEDs | 1–3 mA for low power. |
| Passives | as required | 0603/0805 common values | Prefer common E24/E12 values. |
| Test points | 10–14 | SMT loop/pad test points | Rails, SWD, I2C, PWM, sense. |
Control Thresholds to Start With
- Low battery warning: 3.45 V under light load.
- Low battery shutdown: 3.20 V sustained or 3.0 V immediate cutoff margin.
- Pump soft-start ramp: 0 to target PWM over 2 seconds.
- Stall current: initially set at 1.5–2.0× measured normal current after pump characterization.
- Blocked inlet/outlet: set differential pressure thresholds empirically using test tubing and filters.
- Disconnected tubing: pressure response below baseline threshold while pump current is normal.
Layout Plan
- Board target: approximately 45 mm × 35 mm unless enclosure demands otherwise.
- Place USB-C and charge IC on one edge; battery connector/holder pads on opposite/adjacent edge.
- Place pump connector and MOSFET/current sense close together with a short high-current loop.
- Put MCU central, pressure sensor near tubing edge/ports, and status LEDs on visible edge.
- Use wide VBAT/VSYS/pump copper, local bulk capacitor near pump connector, and a solid ground pour.
- Keep pressure sensor and I2C routing away from pump switching node.
Verification Plan
- ERC: check no floating MCU power pins, all LEDs have resistors, charger pins configured, and no accidental shorts.
- DRC: verify no airwires, no missing footprints, sufficient trace width for pump current, and connector edge clearances.
- Power validation: measure sleep, idle, running, startup, and stall current.
- Flow validation: measure 400 mL/min target with calibrated flow meter and record PWM duty vs flow curve.
- Fault validation: blocked inlet, blocked outlet, disconnected tubing, low battery, and pump unplugged tests.
V1 Limitations
- No closed-loop flow regulation; flow will vary with battery voltage, tubing, filter loading, pump tolerance, and temperature.
- Differential pressure sensor is used for fault detection only.
- Pump acoustic noise depends heavily on selected pump, mounting, enclosure, and PWM frequency.
Recommended Schematic Blocks
Candidate BOM
Control Thresholds to Start With
Layout Plan
Verification Plan
V1 Limitations
