INA219 Current Measurement Audit
Task unable to complete.
2:13
Thought for 16 sec — Identifying necessary skills
Looking up PCB routing cleanup stale traces Q2 reverse polari....
Checking 5 design areas.
Reading schematic details for J1, F2, Q2 and 7 more.
Completed 5 design checks — found 39 issues.
Checking 5 design areas... (28 sec)
Reading layout details for Q2, F2, D3 and 5 more.
Thought for 10 sec
Work done
- Audited the scoped Q2 input-protection area and verified the corrected schematic connectivity.
- DRC still reports scoped layout problems: VIN_FUSED airwire between
F2:P2andQ2:D, VIN_PROTECTED airwires involvingQ2:S,D6:K, andR6:P2, plus stale/dangling trace remnants and an overlap atQ2:D. - Created the detailed status file: Q2 Input Protection Routing Remediation Status.
- ❌ Stale traces were identified but not removed in this run.
- ❌ The physical path is not yet fully routed as
J1 P1 -> F2 -> VIN_FUSED -> Q2 -> VIN_PROTECTED -> D3/C7/FB2 -> VIN_FILTERED. - ❌ DRC is not clean in the scoped area; airwires/dangling/overlap issues remain.
- ✅ The corrected schematic topology still supports reverse-polarity blocking, but the PCB must be cleaned/rerouted before fabrication.
Perform the physical trace cleanup/reroute in the PCB editor for the listed scoped items, then rerun DRC to confirm the Q2 input-protection area is clear.
Locate routing issues
Fix Q2 remnants
Route VIN_PROTECTED
Run targeted DRC
Refine this doc
Ask about this doc
Relay Driver Stage Audit
Date: 2026-05-11
Scope: audit only; no project modifications were made.
Result
Overall: PASS with layout cleanup notes.
The INA219 high-side relay coil sensing topology is logically correct in the schematic, and the PCB review did not report airwires for the checked nets. The one layout concern is that the latest DRC review reports 4 dangling trace warnings, so stale/open copper should be cleaned before fabrication even though it is not specifically reported as a shunt bypass.
Expected topology checked
Expected:
5V / U6 IN+ -> RSHUNT -> RELAY_COIL_HIGH_SENSE / U6 IN- / K1 A1Observed schematic topology:
5V:RSHUNT:P1,U6:IN+,D1:cathode,L1:2,U1:FEEDBACK,C2:1,C4:P1,U2:EXT_5VRELAY_COIL_HIGH_SENSE:RSHUNT:P2,U6:IN-,K1:A1RELAY_COIL_LOW:K1:A2,D1:anode,Q1:CGND:Q1:E,U6:GND,U2:GND1/GND2/GND3,C5:P2,U6:A0,U6:A1, and other ground points
Checklist
Table
| # | Check | Result | Evidence / notes |
|---|---|---|---|
| 1 | U6 IN+ is on the 5V source side of RSHUNT | PASS | U6:IN+ and RSHUNT:P1 are both on net 5V. |
| 2 | U6 IN- is on relay-coil side of RSHUNT | PASS | U6:IN-, RSHUNT:P2, and K1:A1 are all on RELAY_COIL_HIGH_SENSE. |
| 3 | RSHUNT is physically routed in series with actual relay coil current path, not just connected by labels | PASS, with DRC cleanup note | Schematic connectivity forces coil current through RSHUNT before K1:A1, and the latest airwire check did not report open/unrouted shunt/relay nets. However, 4 dangling trace warnings exist and should be cleaned before fabrication. |
| 4 | No alternate copper path bypasses RSHUNT | PASS for steady-state coil current | No schematic path from 5V directly to K1:A1 was found. The flyback diode D1 connects from RELAY_COIL_LOW to pre-shunt 5V; it is reverse-biased while the relay is energized, but it does provide a flyback/transient return path that does not measure through the shunt after turn-off. |
| 5 | INA219 VS is powered from 3.3V | PASS | U6:VS is on 3V3. |
| 6 | SDA/SCL are pulled up to 3.3V, not 5V | PASS | R3 and R4 are 4.7k I2C pull-ups; R3:P2 and R4:P2 are on 3V3, while R3:P1 is I2C_SDA and R4:P1 is I2C_SCL. |
| 7 | INA219 GND is common with ESP32 GND | PASS | U6:GND and U2:GND1/GND2/GND3 are on common GND. |
| 8 | A0/A1 address pins are intentionally tied and not floating | PASS | U6:A0 and U6:A1 are both tied to GND. This selects the all-ground address configuration and is not floating. |
| 9 | C5 100nF decoupling capacitor is close to INA219 VS/GND | MARGINAL PASS / IMPROVE | C5 is 100nF between 3V3 and GND. PCB centers: U6 at (0.87, -17.64) mm, C5 at (4.11, -12.96) mm; center-to-center distance is about 5.7 mm. For a 0603 decoupling capacitor, this is usable but farther than ideal; place C5 closer to U6 VS/GND if possible. |
Complete relay coil current path
When Q1 is on, the intended DC relay coil current path is:
5V rail -> RSHUNT:P1 -> RSHUNT:P2 -> RELAY_COIL_HIGH_SENSE -> K1:A1 -> relay coil -> K1:A2 -> RELAY_COIL_LOW -> Q1:C -> Q1:E -> GNDINA219 sensing points:
- High/source side:
U6:IN+on5V - Low/load side:
U6:IN-onRELAY_COIL_HIGH_SENSE
Can relay coil current bypass RSHUNT?
Steady-state energized relay current: no bypass found.
The only schematic connection to
K1:A1 is through RELAY_COIL_HIGH_SENSE, which includes RSHUNT:P2 and U6:IN-. There is no direct 5V connection to K1:A1 in the schematic data.Transient flyback current note:
D1 connects from RELAY_COIL_LOW to pre-shunt 5V. During relay turn-off, D1 can conduct flyback current into the 5V node, so that transient decay current is not strictly measured as normal shunt current. That is expected for this diode placement, but it means INA219 readings during turn-off transients may not represent coil current through the shunt.Expected shunt voltage
Using
Vshunt = I * R, with RSHUNT = 0.22 ohm:Table
| Coil current | Shunt voltage |
|---|---|
| 70 mA | 15.4 mV |
| 80 mA | 17.6 mV |
| 100 mA | 22.0 mV |
Power in RSHUNT at 100 mA is
I^2R = 0.1^2 * 0.22 = 0.0022 W, far below the intended 0.25 W rating.Layout observations
Relevant component positions from PCB layout:
Table
| Component | Position / placement |
|---|---|
RSHUNT | Top layer, center about (-0.82, -12.96) mm, 1206 package |
U6 | Top layer, center about (0.87, -17.64) mm, SOT-23-8, rotated 90 degrees |
C5 | Top layer, center about (4.11, -12.96) mm, 0603 package |
K1 | Top layer, center about (-16.91, 20.56) mm |
The shunt and INA219 are close to each other, which is good for the sense input pair. K1 is much farther away, but that is not a functional issue if the high-current copper from
RSHUNT:P2 to K1:A1 is routed with adequate width and does not branch around the shunt.Layout corrections needed
- Clean dangling traces before fabrication. Latest DRC reports 4 dangling trace warnings: Trace 1855, Trace 45f1, Trace 4f4c, and Trace 8aa5. These are stale/open copper risks and should be removed or re-routed.
- Move C5 closer to U6 VS/GND if practical. It is currently about 5.7 mm center-to-center from U6; a tighter local bypass placement near the VS/GND pins is preferred.
- After cleanup, re-run DRC and specifically confirm no airwires remain on
5V,RELAY_COIL_HIGH_SENSE, andRELAY_COIL_LOW. - Visually inspect copper on
5VandRELAY_COIL_HIGH_SENSEafter routing cleanup to confirm no same-net or stale copper creates an unintended direct bridge around RSHUNT.
Final verdict
PASS for the INA219 high-side relay coil measurement topology and intended shunt value/properties.
Action before fabrication: clean dangling traces and improve C5 placement if possible; then re-run DRC.
Result
Expected topology checked
Checklist
Complete relay coil current path
Can relay coil current bypass RSHUNT?
Expected shunt voltage
Layout observations
Layout corrections needed
Final verdict
