PCB Design for Motor Monitoring
Now help me finish the connections
Thought for 5 sec
I’ll finish the schematic connections by first reading the current component pins and uploaded measurement/sensor/connector data, then I’ll wire the sensor, protection, isolation, Dspace connector, and test-point nets and run review checks.
Worked for 6 mins 4 sec
Finished the schematic connections for the current measurement interface: LV25-P voltage channel, LA25-P current secondary channel, ±15 V isolated sensor supplies, AGND return, burden resistors, TVS output protection, temporary dSPACE output connector, and labeled TP1/TP2 test points.
I updated the measurement/safety project file: DFIG Measurement Interface — Project Requirements. ERC now reports clean; DRC airwires remain because the board has not been placed/routed yet.
Remaining before layout/manufacture: replace temporary J2 with the exact TE 1761028-5 100-pin dSPACE connector when available, resolve the current-sensor primary/turns footprint representation, then proceed to placement and routing after your confirmation.
Add exact J2
Resolve U2 footprint
Run ERC/DRC
Set up layout
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Regulator and Passive Selection
Scope
Selection guidance for the DFIG motor terminal measurement interface using:
- LEM LV 25-P voltage transducer
- LEM LA 25-NP current transducer
- D-sub/CLP1104 interface to dSPACE DS1104/CLP1104 analog inputs
- Hand-solderable implementation preference
The current schematic is still empty, so this is a selection brief for the components to add next.
Datasheet-derived requirements
LEM LV 25-P voltage transducer
- Requires bipolar supply: ±12 V to ±15 V, ±5%.
- Current consumption: 10 mA at ±15 V + secondary output current.
- Secondary nominal current: 25 mA.
- Recommended burden resistor range at ±15 V:
- At ±10 mA primary max: 100 Ω to 350 Ω
- At ±14 mA primary max: 100 Ω to 190 Ω
- Galvanic isolation: 2.5 kV rms, 50 Hz, 1 min between primary and secondary.
- Creepage/clearance: 19.5 mm.
- Input voltage measurement requires external primary resistor R1, selected so nominal measured voltage produces 10 mA primary current.
- Example: 250 V nominal → 25 kΩ / 2.5 W primary resistor.
LEM LA 25-NP current transducer
- Requires bipolar supply: ±15 V, ±5%.
- Current consumption: 10 mA + secondary output current.
- Secondary nominal current: 25 mA.
- Recommended burden resistor range at ±15 V:
- At ±25 A max: 100 Ω to 320 Ω
- At ±36 A max: 100 Ω to 190 Ω
- Galvanic isolation: 2.5 kV rms, 50 Hz, 1 min.
- Creepage/clearance: 10.63 mm.
- Configurable primary turns support nominal ranges from 25 A down to 5 A depending on pin interconnection.
dSPACE DS1104/CLP1104 analog inputs
- A/D converter input voltage range: ±10 V.
- Multiplexed channels: 16-bit; parallel channels: 12-bit.
- The slave DSP A/D converter inputs are 0…5 V, so use the main ±10 V ADC inputs unless the design intentionally targets the slave DSP inputs.
Power budget
For one LV 25-P and one LA 25-NP:
Table
| Load | Supply | Approx. load per rail |
|---|---|---|
| LV 25-P | ±15 V | 10 mA + 25 mA = 35 mA |
| LA 25-NP | ±15 V | 10 mA + 25 mA = 35 mA |
| Analog protection/filtering margin | ±15 V | ~10–20 mA allowance |
| Recommended regulator capacity | ±15 V | ≥100 mA per rail minimum |
Recommended design target: choose a ±15 V supply rated at least 100 mA per rail, preferably 3 W or higher for margin and future channels.
Recommended regulator approach
Best fit: isolated dual-output ±15 V DC/DC module
Use an isolated DC/DC converter module rather than generating ±15 V from the 9 V battery directly. The LEM sensors already provide measurement isolation, but an isolated analog supply improves safety boundaries and reduces ground-loop risk between the motor terminal box and dSPACE interface.
Flux library candidates found:
Table
| Option | Flux part | Why suitable |
|---|---|---|
| Primary recommendation | JTD1524D15 | XP Power isolated dual output ±15 V, 500 mA per rail, 9–36 V input, 6-DIP through-hole, hand-solderable. |
| Alternative | TEN-20-2423WIN | Traco Power isolated dual output ±15 V, ~665 mA per rail, 9–36 V input, 6-DIP through-hole, widely available. |
| Alternative | CCG15-24-15D | TDK-Lambda isolated dual output ±15 V, 500 mA per rail, 9–36 V input; confirm mechanical pin style before PCB finalization. |
Recommended supply architecture:
Text
External 12–24 V DC input → input fuse / reverse-polarity protection / TVS → isolated ±15 V DC/DC module → LC or RC cleanup filtering → ±15VA rails for LV 25-P and LA 25-NP
Alternative: 7815/7915 linear regulators
A through-hole 7815 exists in the Flux library, but a matching 7915 was not found. This option also requires an existing unregulated dual supply above ±17–18 V and wastes heat, so it is less attractive than the isolated DC/DC module.
Sensor output burden resistors
Both LEM transducers provide current output, so convert to voltage using burden resistors.
Recommended burden value
Use 200 Ω precision burden resistors if operating at nominal 25 mA secondary output:
Text
Vout = Is × RM = 25 mA × 200 Ω = 5.0 V nominal
This keeps the sensor output safely inside the dSPACE ±10 V range and provides headroom for transients and scaling.
Power in each burden resistor:
Text
P = I²R = (25 mA)² × 200 Ω = 0.125 W
Use at least 0.25 W, preferably 0.5 W, and 1% or better tolerance. For calibrated measurement, use 0.1% if available.
Flux library note: exact 200 Ω through-hole precision part was not found in the broad search. A through-hole 1 kΩ 0.5 W metal-film family was found; use the same family if a 200 Ω value is available, or accept an SMD precision resistor if measurement accuracy is more important than pure through-hole assembly.
Analog output protection and filtering to dSPACE
Per measurement output channel:
Text
LEM output current → 200 Ω burden → 1 kΩ series resistor → dSPACE analog input | clamp/protection | AGND / ± rails
Recommended per-channel passives:
Table
| Function | Value / type | Notes |
|---|---|---|
| Burden resistor | 200 Ω, 0.1–1%, ≥0.25 W; 0.5 W preferred | Converts 25 mA sensor output to 5 V nominal. |
| Series protection resistor | 1 kΩ, 0.25–0.5 W | Limits fault current into dSPACE input and clamps. |
| Input RC filter capacitor | 10 nF to 100 nF film or C0G/X7R to AGND | With 1 kΩ, 100 nF gives ~1.6 kHz cutoff. Use lower capacitance if higher bandwidth is needed. |
| Clamp diodes | Schottky/BAV99-style to ±10 V or ±15 V rails, or bidirectional TVS | Protects dSPACE input from overvoltage. |
| Rail decoupling | 100 nF ceramic + 10 µF electrolytic per rail near each sensor/supply entry | Hand-solderable radial parts preferred. |
Library candidates found for hand-solderable passives:
Table
| Function | Flux part | Notes |
|---|---|---|
| 1 kΩ series resistor | CMF551K0000FKR6 | 1 kΩ ±1%, 0.5 W through-hole metal-film. |
| 100 nF decoupling/filter capacitor | K104K10X7RF5TH5 | 100 nF, 50 V, X7R radial through-hole. |
| 10 µF bulk capacitor | EEA-FC1E100 | 10 µF, 25 V radial electrolytic; use higher voltage rating if placed across rails or on >15 V input. |
Primary-side motor terminal protection
The motor terminal side is hazardous and must be handled as a high-voltage/high-energy domain.
For each voltage measurement input:
- Use appropriately rated high-voltage series resistor network for LV 25-P primary current setting.
- Size for measured nominal voltage using:
Text
R1 = Vnominal / 10 mA P = Vnominal × 10 mA
Examples:
- 250 V nominal → 25 kΩ, 2.5 W minimum; use multiple HV resistors in series for voltage and power sharing.
- 500 V nominal → 50 kΩ, 5 W minimum; use multiple HV resistors in series.
Add:
- HV fuse or fusible resistor at each measurement tap.
- MOV or surge suppressor appropriate to the motor terminal voltage category.
- RC/EMI filtering only if it does not compromise measurement bandwidth or safety ratings.
- PCB creepage/clearance consistent with motor voltage and pollution degree; keep primary and secondary domains physically separated.
For current measurement:
- Route motor/slip-ring current conductor through the LA 25-NP primary turns as required for the selected measurement range.
- Ensure conductor and connector current ratings exceed motor current.
- Keep high-current primary routing separated from low-level analog output routing.
Parts still requiring confirmation
- Exact motor terminal voltage range: needed to calculate LV 25-P primary resistor values and power ratings.
- Exact stator/slip current range: needed to choose LA 25-NP primary turns configuration.
- Available auxiliary supply: recommended DC/DC modules assume 9–36 V or 12–24 V DC input, not a small 9 V block battery.
- Whether SMD protection diodes/TVS are acceptable; through-hole protection parts were not found cleanly in the Flux library search.
- D-sub/CLP1104 pinout: the uploaded D-sub connector datasheet did not return useful searchable text, so its exact pin count and wiring style need a more targeted query or user confirmation.
Recommended next schematic additions
- Add isolated ±15 V DC/DC module: JTD1524D15 preferred.
- Add input protection for the DC/DC input: fuse/PTC, reverse polarity diode or ideal diode, input TVS, input bulk capacitor.
- Add ±15 V rail decoupling: 100 nF + 10 µF per rail near each sensor.
- Add LV 25-P and LA 25-NP sensor output burden resistors: 200 Ω precision, ≥0.25 W.
- Add analog output protection: 1 kΩ series resistor, RC capacitor, clamp network per dSPACE input channel.
- Add high-voltage primary resistor networks and fusing once motor voltage range is confirmed.
Scope
Datasheet-derived requirements
LEM LV 25-P voltage transducer
LEM LA 25-NP current transducer
dSPACE DS1104/CLP1104 analog inputs
Power budget
Recommended regulator approach
Best fit: isolated dual-output ±15 V DC/DC module
Alternative: 7815/7915 linear regulators
Sensor output burden resistors
Recommended burden value
Analog output protection and filtering to dSPACE
Primary-side motor terminal protection
Parts still requiring confirmation
Recommended next schematic additions
