INA219 Current Measurement Audit
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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
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INA219 Relay Coil Current Sense Audit
AUDIT ONLY — no schematic or PCB modifications performed.
Verdict
PASS with layout warnings. The INA219 high-side relay coil current measurement topology matches the intended electrical function:
5V / U6 IN+ -> RSHUNT -> RELAY_COIL_HIGH_SENSE / U6 IN- / K1 A1. I found no schematic alternate path that bypasses RSHUNT for relay coil high-side current.Requirement-by-requirement checks
Table
| # | Check | Result | Evidence / notes |
|---|---|---|---|
| 1 | U6 IN+ is on the 5V source side of RSHUNT | PASS | Net 5V connects RSHUNT:P1 and U6:IN+, along with the 5V rail nodes. |
| 2 | U6 IN- is on the relay-coil side of RSHUNT | PASS | Net RELAY_COIL_HIGH_SENSE connects RSHUNT:P2, U6:IN-, and K1:A1. |
| 3 | RSHUNT is physically routed in series with relay coil current path, not just labels | PASS | PCB copper for 5V routes to RSHUNT:P1; separate copper net RELAY_COIL_HIGH_SENSE routes from RSHUNT:P2 to K1:A1 and U6:IN-. |
| 4 | No alternate copper path bypasses RSHUNT | PASS based on available layout data | I found no direct 5V connection to K1:A1; K1:A1 is only on RELAY_COIL_HIGH_SENSE. |
| 5 | INA219 VS powered from 3.3V | PASS | Net 3V3 connects U6:VS. |
| 6 | SDA/SCL pulled up to 3.3V, not 5V | PASS | R3 and R4 are 4.7 kΩ I2C pull-ups; their upper pins connect to 3V3, and their lower pins connect to I2C_SDA / I2C_SCL. |
| 7 | INA219 GND common with ESP32 GND | PASS | U6:GND is on the common GND net, which also includes ESP32 DevKit ground pins. |
| 8 | A0/A1 address pins tied intentionally, not floating | PASS | U6:A0 and U6:A1 are both tied to GND. |
| 9 | C5 100 nF decoupling capacitor close to INA219 VS/GND | WARNING | Electrically correct: C5:P1 -> 3V3, C5:P2 -> GND. Physically, C5 is about 5.7 mm center-to-center from U6, northeast of the INA219. This is nearby but not tight decoupling placement. |
Complete relay coil current path
Nominal energized relay coil current path is:
5V rail -> RSHUNT:P1 -> RSHUNT 0.22 ohm -> RSHUNT:P2 -> RELAY_COIL_HIGH_SENSE -> K1:A1 -> relay coil -> K1:A2 -> RELAY_COIL_LOW -> Q1 collector -> Q1 emitter -> GNDINA219 measurement nodes:
U6:IN+senses the source side of the shunt on net5V.U6:IN-senses the load/relay side of the shunt on netRELAY_COIL_HIGH_SENSE.U6:VSis powered from3V3.U6:GND,U6:A0, andU6:A1are tied toGND.U6:SDAandU6:SCLconnect to ESP32 I2C nets with 4.7 kΩ pull-ups to3V3.
Can relay current bypass RSHUNT?
No bypass found. In the schematic,
K1:A1 is not connected directly to 5V; it is on RELAY_COIL_HIGH_SENSE, which is fed from RSHUNT:P2. In the PCB layout data, 5V and RELAY_COIL_HIGH_SENSE are distinct routed nets, with the shunt bridging them.Expected shunt voltage
Using intended
RSHUNT = 0.22 ohm:Table
| Relay coil current | Shunt voltage V = I × R | Shunt power P = I² × R |
|---|---|---|
| 70 mA | 15.4 mV | 1.08 mW |
| 80 mA | 17.6 mV | 1.41 mW |
| 100 mA | 22.0 mV | 2.20 mW |
The 0.25 W shunt power rating has very large margin for this relay-coil current range.
PCB layout observations
Acceptable
RSHUNTis placed near U6:RSHUNTcenter at approximately(-0.825 mm, -12.9565 mm), U6 center at approximately(0.8722 mm, -17.6444 mm).5VandRELAY_COIL_HIGH_SENSEare routed as separate nets bridged only byRSHUNT.- There is no layout evidence of a direct 5V-to-K1-A1 bypass.
Warnings / corrections before production
- Move C5 closer to U6 VS/GND if revising layout. C5 is ~5.7 mm center-to-center from U6. For production-grade layout, the decoupling capacitor should be tucked next to the INA219 supply pins with the shortest possible VS/GND loop.
- Consider widening the long
RELAY_COIL_HIGH_SENSEcurrent trace. The existing routed trace is shown as 0.15 mm in the extracted layout. It is electrically acceptable for ~70–100 mA, but a wider trace would be more robust and lower impedance for a relay coil supply path. - Keep the INA219 Kelvin/sense topology clean. The present schematic is logically correct, but if the layout is revised, avoid routing relay load current through the same narrow copper segment used only for INA219 sense into
U6:IN-. - Unrelated DRC warning remains: current DRC reports 4 dangling traces. I did not verify these are part of the INA219 stage; they should be cleared before fabrication regardless.
Final conclusion
PASS for INA219 high-side relay coil current measurement topology. The electrical net assignment is correct,
RSHUNT is in series with the relay coil high side, INA219 supply and I2C pull-ups are on 3.3 V, address pins are intentionally tied low, and no shunt bypass was found. The main issue is layout quality: improve C5 placement and consider a wider relay high-side current trace before production release.Verdict
Requirement-by-requirement checks
Complete relay coil current path
Can relay current bypass RSHUNT?
Expected shunt voltage
PCB layout observations
Acceptable
Warnings / corrections before production
Final conclusion
