Relay Board Design Improvements

flux

1:36

Next gen (beta)
Project
Knowledge Base
Schematic
U2

Using Knowledge Base Tool.

Using Schematic Tool.

Great project. Based on your current schematic and Flux knowledge base guidance, here are focused, high‑impact improvements for reliability, EMC, and expandability. I’ve tailored the notes to what’s already in your design.
Power and decoupling
  1. 3.3 V rail decoupling (MCU, shift register, Ethernet)
  • Place a local 100 nF ceramic right at each VCC pin of:
    • U1 ESP32-S3 module (one per VCC/GND pair, within 5 mm).
    • U2 74HC595.
    • WETH WIZ850io socket.
  • Keep your existing bulk on 3.3 V (C2 10 µF and C5 10 µF), but add one mid-value (1 µF) near U1/U2 if trace length is >2–3 cm. A typical combo per KB guidance is 100 nF + 1 µF + 10 µF.
  • Verify the 3.3 V portal net “Net 57” starves no device; route a short, wide 3.3 V spine with stubs to each IC.
  1. AMS1117 stability and thermal
  • The AMS1117-3.3 (U3) needs its recommended input/output capacitors close to pins (you already have C1 1 µF on VIN and C2 10 µF on VOUT). Check the datasheet for minimum ESR and recommended values to ensure loop stability and adjust C1/C2 values/types accordingly.
  • Estimate load: ESP32 + W5500 module + LEDs + 74HC595. If total >200–300 mA, the AMS1117 may dissipate significant heat from 12 V input. Consider:
    • Pre‑regulate 12 V down to 5–6 V with a small buck before the LDO, or
    • Replace with a pin‑compatible but lower‑drop/thermal LDO only if your input is already lower. Otherwise, a buck to 3.3 V is more efficient.
Relay drive integrity and protection 3) Flyback path
  • One diode is visible (D9) tied to the shift‑register feedback net. Instead, ensure each relay coil (on each module RELAY1 … RELAY8) includes a direct flyback path across the coil: cathode to +12 V, anode to coil low side.
  • Based on Flux knowledge base, size diode current rating ≥ relay coil steady‑state current; ensure reverse voltage rating > supply + margin (e.g., ≥20 V for 12 V systems).
  • If your relay modules include on‑board diodes already, great—document that on schematic. If not, add one per coil.
  1. Shift‑register outputs to relay drivers
  • Currently U2 outputs drive “IN” pins of relay modules. 74HC595 cannot source/sink high current; typically you should use a transistor/driver array (e.g., ULN2803 patterns) between U2 and coils if the module input isn’t logic‑level with low current.
  • Action: clarify what “IN” expects on your gRelay modules. If it is a logic input to an onboard driver, keep it. If it expects coil current, add drivers.
Signal integrity and expansion bus 5) 74HC595 chain and control lines
  • You have SR_DATA, SR_CLOCK, SR_LATCH nets from U1 to U2 and out to J9 with QH’ on “Net 48” for daisy‑chain. Good.
  • For expansion cables:
    • Add series damping resistors (22–68 Ω) near the driver on SCK/RCK/SI if cable length >20–30 cm to tame ringing.
    • Provide a solid GND return and 3.3 V on the header. You already route 12 V widely; include 3.3 V on the expansion header only if remote logic needs it.
    • Pulls: add a weak pull‑down (e.g., 100 kΩ) on ~SCLR and ~G to a defined idle if they can float during boot. Right now ~SCLR ties via portal Net “SR_CLEAR” to ESP; consider a local pull‑up to VCC for fail‑safe.
    • Decouple each downstream 74HC595 with its own 100 nF at the IC.
Ethernet module (WIZ850io) 6) Power and SPI lines
  • Ensure WETH 3.3 V pin has a nearby 100 nF + 10 µF to ground and a short return to the main 3.3 V plane (you already tie it to Net 57; add local decoupling at the socket).
  • Keep SPI traces (SCLK, MOSI, MISO, nCS) short, length-matched isn’t critical at low MHz but avoid long stubs; include 22–33 Ω series resistors at the ESP32 side if you observe ringing.
USB and ESD 7) USB D+/D-
  • You break out USB_D and USB_D- to ESP pins. For robustness:
    • Add a USB data‑line ESD TVS with capacitance <1 pF per line close to the connector. The Flux knowledge base recommends bidirectional TVS for USB data protection with ultra‑low capacitance.
Grounding and planes 8) Solids over stars
  • Per the Flux knowledge base, use a solid ground plane rather than star grounds for best EMC and ESD return. Keep high current relay returns on the same solid plane; segregate by routing, not by splitting ground, unless you truly isolate with optos.
User IO and status 9) LED resistors
  • R2=220 Ω and R4=220 Ω look like current‑limiters for LED2/LED3. Confirm current at 3.3 V meets LED spec; adjust to brightness vs. power target. R3=550 Ω for LED1 seems fine for a softer indicator.
Boot and reset handling (ESP32-S3) 10) EN and boot pins
  • You connected EN to SW2 and added C3=100 nF to EN; include a pull‑up on EN (typically 10 kΩ to 3.3 V) if the module doesn’t include it, to guarantee clean startup.
  • IO0 boot mode: You have SW1 tied to IO0 net. Ensure a default pull-up on IO0 if not on module, so normal boot is guaranteed when the button isn’t pressed.
Connectors and power entry 11) Power entry connector
  • J11 shows A/B/C with A tied to Net 1 (12 V) and B to GND. Add input protection:
    • Reverse‑polarity protection (ideal diode or series diode), and
    • Transient suppression on 12 V input (e.g., an automotive‑style TVS if long wiring is expected), and
    • Bulk electrolytic (e.g., 47–100 µF) at the input connector for relay surge demand, plus a 100 nF ceramic.
Documentation and testability 12) Label expansion nets
  • Clearly label SR_DATA, SR_CLOCK, SR_LATCH, SR_DOUT directions and voltage level on J9. Add a pinout table on silk in PCB.
  • Add test pads for 3.3 V, GND, SR lines, and EN/IO0 for bring‑up.
Layout guidance (for when you route) 13) Keep loops tight
  • Place decouplers on the same side as the IC, as close as possible to the power pins, with direct via to the ground plane.
  • Route 12 V relay distribution as a wide polygon or fat traces, with local decoupling near each relay module header.
Would you like me to:
  • Add the missing 100 nF decouplers at U1/U2/WETH, plus EN and IO0 pull‑ups, and per‑coil flyback diodes where needed?
  • Add series resistors on SR_CLOCK/SR_LATCH/SI and SPI, and ESD protection for USB D+/D-? If you say yes, I can propose the exact parts and place them for you.
Add decouplers/pull-ups
Add flyback diodes
Add series resistors
Add USB ESD protection
201 days

Ready.

Sign up to send
U3
RELAY6
RELAY3
RELAY2
RELAY4
RELAY7
RELAY1
RELAY8
U1
RELAY5
SR_FEEDBACK
RELAY2
UART_TXD0
RELAY5
RELAY7
SR_FB
RELAY5
TDO
RELAY6
UART_RXD0
SR_LATCH
TMS
USB_D+
SR_CLOCK
SR_DATA
ESP_EN
RELAY4
SR_FEEDBACK
SR_DATA
SR_DOUT
RELAY3
USB_D-
SR_DOUT
RELAY1
SR_CLOCK
TCK
RELAY4
RELAY3
SR_LATCH
SR_LATCH
RELAY2
RELAY7
IO1
RELAY1
RELAY6
SR_CLOCK
RELAY0
TDI
SR_CLEAR
RELAY0
C2
Capacitance
10u F
SW2
12V
LED1
12V
12V
3V3
C5
Capacitance
10u F
C3
Capacitance
0.1u F
CN3
12V
3V3
LED2
C4
Capacitance
0.1u F
12V
LED3
12V
3V3
3V3
R4
Resistance
220 Ω
U2
12V
12V
12V
J13
12V
R2
Resistance
220 Ω
12V
SW1
D9
C1
Capacitance
1u F
J9
R3
Resistance
550 Ω
  • Ground
    Ground
    A common return path for electric current. Commonly known as ground.
    jharwinbarrozo
    20.5M
  • Net Portal
    Net Portal
    Wirelessly connects nets on schematic. Used to organize schematics and separate functional blocks. To wirelessly connect net portals, give them same designator. #portal
    jharwinbarrozo
    43.0M
  • Power Net Portal
    Power Net Portal
    Wirelessly connects power nets on schematic. Identical to the net portal, but with a power symbol. Used to organize schematics and separate functional blocks. To wirelessly connect power net portals, give them the same designator. #portal #power
    jharwinbarrozo
    11.4M
  • Generic Resistor
    Generic Resistor
    A generic fixed resistor for rapid developing circuit topology. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard resistor values: 1.0Ω 10Ω 100Ω 1.0kΩ 10kΩ 100kΩ 1.0MΩ 1.1Ω 11Ω 110Ω 1.1kΩ 11kΩ 110kΩ 1.1MΩ 1.2Ω 12Ω 120Ω 1.2kΩ 12kΩ 120kΩ 1.2MΩ 1.3Ω 13Ω 130Ω 1.3kΩ 13kΩ 130kΩ 1.3MΩ 1.5Ω 15Ω 150Ω 1.5kΩ 15kΩ 150kΩ 1.5MΩ 1.6Ω 16Ω 160Ω 1.6kΩ 16kΩ 160kΩ 1.6MΩ 1.8Ω 18Ω 180Ω 1.8KΩ 18kΩ 180kΩ 1.8MΩ 2.0Ω 20Ω 200Ω 2.0kΩ 20kΩ 200kΩ 2.0MΩ 2.2Ω 22Ω 220Ω 2.2kΩ 22kΩ 220kΩ 2.2MΩ 2.4Ω 24Ω 240Ω 2.4kΩ 24kΩ 240kΩ 2.4MΩ 2.7Ω 27Ω 270Ω 2.7kΩ 27kΩ 270kΩ 2.7MΩ 3.0Ω 30Ω 300Ω 3.0KΩ 30KΩ 300KΩ 3.0MΩ 3.3Ω 33Ω 330Ω 3.3kΩ 33kΩ 330kΩ 3.3MΩ 3.6Ω 36Ω 360Ω 3.6kΩ 36kΩ 360kΩ 3.6MΩ 3.9Ω 39Ω 390Ω 3.9kΩ 39kΩ 390kΩ 3.9MΩ 4.3Ω 43Ω 430Ω 4.3kΩ 43KΩ 430KΩ 4.3MΩ 4.7Ω 47Ω 470Ω 4.7kΩ 47kΩ 470kΩ 4.7MΩ 5.1Ω 51Ω 510Ω 5.1kΩ 51kΩ 510kΩ 5.1MΩ 5.6Ω 56Ω 560Ω 5.6kΩ 56kΩ 560kΩ 5.6MΩ 6.2Ω 62Ω 620Ω 6.2kΩ 62KΩ 620KΩ 6.2MΩ 6.8Ω 68Ω 680Ω 6.8kΩ 68kΩ 680kΩ 6.8MΩ 7.5Ω 75Ω 750Ω 7.5kΩ 75kΩ 750kΩ 7.5MΩ 8.2Ω 82Ω 820Ω 8.2kΩ 82kΩ 820kΩ 8.2MΩ 9.1Ω 91Ω 910Ω 9.1kΩ 91kΩ 910kΩ 9.1MΩ #generics #CommonPartsLibrary
    jharwinbarrozo
    1.5M
  • Generic Capacitor
    Generic Capacitor
    A generic fixed capacitor ideal for rapid circuit topology development. You can choose between polarized and non-polarized types, its symbol and the footprint will automatically adapt based on your selection. Supported options include standard SMD sizes for ceramic capacitors (e.g., 0402, 0603, 0805), SMD sizes for aluminum electrolytic capacitors, and through-hole footprints for polarized capacitors. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard capacitor values: 1.0pF 10pF 100pF 1000pF 0.01uF 0.1uF 1.0uF 10uF 100uF 1000uF 10,000uF 1.1pF 11pF 110pF 1100pF 1.2pF 12pF 120pF 1200pF 1.3pF 13pF 130pF 1300pF 1.5pF 15pF 150pF 1500pF 0.015uF 0.15uF 1.5uF 15uF 150uF 1500uF 1.6pF 16pF 160pF 1600pF 1.8pF 18pF 180pF 1800pF 2.0pF 20pF 200pF 2000pF 2.2pF 22pF 20pF 2200pF 0.022uF 0.22uF 2.2uF 22uF 220uF 2200uF 2.4pF 24pF 240pF 2400pF 2.7pF 27pF 270pF 2700pF 3.0pF 30pF 300pF 3000pF 3.3pF 33pF 330pF 3300pF 0.033uF 0.33uF 3.3uF 33uF 330uF 3300uF 3.6pF 36pF 360pF 3600pF 3.9pF 39pF 390pF 3900pF 4.3pF 43pF 430pF 4300pF 4.7pF 47pF 470pF 4700pF 0.047uF 0.47uF 4.7uF 47uF 470uF 4700uF 5.1pF 51pF 510pF 5100pF 5.6pF 56pF 560pF 5600pF 6.2pF 62pF 620pF 6200pF 6.8pF 68pF 680pF 6800pF 0.068uF 0.68uF 6.8uF 68uF 680uF 6800uF 7.5pF 75pF 750pF 7500pF 8.2pF 82pF 820pF 8200pF 9.1pF 91pF 910pF 9100pF #generics #CommonPartsLibrary
    jharwinbarrozo
    1.5M
  • Generic Inductor
    Generic Inductor
    A generic fixed inductor for rapid developing circuit topology. *You can now change the footprint and 3D model at the top level anytime you want. This is the power of #generics
    jharwinbarrozo
    15.3k
  • Terminal
    Terminal
    An electrical connector acting as reusable interface to a conductor and creating a point where external circuits can be connected.
    natarius
  • RMCF0805JT47K0
    RMCF0805JT47K0
    47 kOhms ±5% 0.125W, 1/8W Chip Resistor 0805 (2012 Metric) Automotive AEC-Q200 Thick Film #forLedBlink
    jharwinbarrozo
    1.2M
  • 875105359001
    875105359001
    10uF Capacitor Aluminum Polymer 20% 16V SMD 5x5.3mm #forLedBlink #commonpartslibrary #capacitor #aluminumpolymer #radialcan
    jharwinbarrozo
    1.2M
  • CTL1206FYW1T
    CTL1206FYW1T
    Yellow 595nm LED Indication - Discrete 1.7V 1206 (3216 Metric) #forLedBlink
    jharwinbarrozo
    1.1M

Inspect

gRelay Board

gRelay Board
Created
Last updated by gficher
1 Contributor(s)
gficher

Controls

Properties

Availability & Pricing

DistributorQty 1

Assets