4.3 Connect External Relay
Hardware Connection · Use the C-connector outputs or another compatible protected control interface
ℹ️
Recommended method: use the V4.7B C connector with a PiBot IsoSwitch V4 or another compatible optically isolated relay-input module. This provides three clear control channels without taking over the PWM or laser headers.
⚠️
Keep the controller side low voltage. Do not route mains wiring through a V4.7B logic connector. Relay contact wiring must use suitable fusing, enclosure, wire size, grounding and a device rated for the real load and surge current.
V4.7B C Connector
EN · STP · DIR · GND
EN · STP · DIR · GND
➜
IsoSwitch Inputs
S1 · S2 · S3 · GND
S1 · S2 · S3 · GND
➜
Relay Contacts
NC · COM · NO
NC · COM · NO
1
Prepare the IsoSwitch V4
- Read the PiBot IsoSwitch V4 documentation and verify the exact relay-board revision.
- Provide the relay board with its specified DC supply. The illustrated version accepts 4.5–40 V DC and is normally used with 24 V.
- For the supplied V4.7B test YAML, set S1/S2/S3 for active-high triggering.
- Confirm the jumper orientation before applying power; do not move jumpers while powered.
IsoSwitch V4 input power, S1/S2/S3/GND and trigger-jumper reference. Verify the silkscreen on your own revision.
2
Connect V4.7B C to S1 / S2 / S3
| V4.7B C connector | IsoSwitch input | Test-YAML function | Test command |
|---|---|---|---|
| EN · I2SO.23 | S1 | Mist / relay channel 1 | M7 on · M9 off |
| STP · I2SO.21 | S2 | Flood / relay channel 2 | M8 on · M9 off |
| DIR · I2SO.20 | S3 | Digital output 0 / relay channel 3 | M64 P0 on · M65 P0 off |
| GND | GND | Signal reference | Required |
- Power off the V4.7B and relay board before wiring.
- Connect each signal exactly as shown in the table.
- Connect the controller signal GND to the IsoSwitch input GND.
- Keep relay contact/load wiring disconnected for the first control test.
3
Test the Three Relay Channels
Power the low-voltage control side and send one command at a time.
M7→S1 / relay 1 turns on. Send M9 and confirm it turns off.M8→S2 / relay 2 turns on. Send M9 and confirm it turns off.M64 P0→S3 / relay 3 turns on. Send M65 P0 and confirm it turns off.- Verify that only the selected relay changes state.
- Test boot, reset, alarm and communication-loss behavior before connecting a load.
4
Use NC / COM / NO Correctly
| Contact | State while relay is inactive | Typical use |
|---|---|---|
| COM | Common moving contact | Connects to NC or NO depending on relay state |
| NO | Open | Load turns on only when relay is energized |
| NC | Closed to COM | Load path opens when relay is energized |
💡
Choose NO or NC from the required safe state, not merely convenience. Test with a continuity meter before connecting the real load.
5
Other V4.7B Control Options
C Connector · RecommendedThree dedicated test outputs with simple M7/M8/M64 commands and one GND reference.
GPIO.4 / GPIO.12 HeadersCompatible 5 V logic relay inputs may be configured here, but these signals are shared with PWM/laser and the matching MOSFET channels.
MOSFET Low-Side ChannelsFor a compatible small DC coil only, with correct flyback protection. Maximum 1.5 A per channel; heavier loads require a suitable external driver.
✓
Commissioning Check
- Each relay responds only to its assigned command.
- All relays return to the intended safe state after stop, reset, alarm and communication loss.
- The control wiring remains cool and stable.
- NC/COM/NO operation is confirmed with a continuity meter before the real load is connected.