ST-DC4 4CH Relay (v2.2.1) · Richmat HJH5 · L&P 50 II · Built by Gary
REV 1.0 // KAREN'S BED
⚠ VERIFY PINOUT FIRST — Before cutting the extension cable, use a multimeter in continuity mode to confirm which pins correspond to Head Up, Head Down, and Common. The pinout below is typical but must be field-verified.
Wire Color Key
Common (shared return)
Head Up signal
Head Down signal
Unused pins (pass through)
Wiring Diagram
Build Steps
01
Verify Pinout
Plug extension cable between remote and control box. Set multimeter to continuity mode. Press each button and probe all 5 pins to identify Common, Head Up, and Head Down. Write it down.
02
Cut & Strip
Cut extension cable at midpoint — leave ~6 inches each side. Strip 8mm of insulation from all 10 wire ends. Tin each wire tip with solder to prevent fraying.
03
Splice Wires
Each wire gets rejoined straight through (Karen's remote stays fully functional). The Common, Head Up, and Head Down wires each also get a pigtail branch to the relay. Solder + heat shrink every junction.
04
Terminate Relay
Screw pigtails into relay terminals. Head Up → NO1 & COM1. Head Down → NO2 & COM2. Use NO terminals only, never NC. Power via USB 5V charger into Micro USB port.
Relay Terminal Map
NO1
Head Up wire — pigtail from Pin 2
COM1
Common wire — pigtail from Pin 1
NO2
Head Down wire — pigtail from Pin 3
COM2
Common wire — second pigtail from Pin 1
NO3
Future use — LED strip / lamp
COM3
Future use
NO4
Future use — Fan / white noise
COM4
Future use
Smart Life App Setup
1
Download Smart Life app on Karen's phone. Create account. Make sure phone is on 2.4GHz WiFi — not 5GHz.
2
Power on the relay board via USB. Open Smart Life → Add Device. It auto-discovers via Bluetooth — tap to add.
3
In device settings, set CH1 and CH2 to Momentary / Inching mode. Set pulse time to 0.5–1 second. This simulates a button press.
4
Open Alexa app → Skills → search Smart Life → Enable → link account → Discover Devices. All 4 channels appear.
5
Rename devices in Alexa: CH1 → "Bed Head Up", CH2 → "Bed Head Down". Build routines as needed.
Suggested Alexa Routines
Trigger phrase
"Alexa, raise the head"
CH1 pulse (Head Up)
Trigger phrase
"Alexa, lower the head"
CH2 pulse (Head Down)
Trigger phrase
"Alexa, flat bed"
CH2 ON for 30 secondsCH2 OFF (fully flat)
Trigger phrase
"Alexa, goodnight Karen"
CH2 ON (lower head)Wait 20 secondsCH2 OFFLights dim to 10%