Relay Logic Wrong Positive vs Negative

Your relay behaves opposite to what the dashboard shows ON when it should be OFF, or OFF when it should be ON. This is a logic configuration issue, not a hardware failure. This guide explains Positive Logic vs Negative Logic and how to fix the setting.

Last updated: April 22, 2026 | 8 min read

Symptoms

• Dashboard shows relay ON but device is OFF
• Relay clicks when you turn it OFF
• Relay works correctly but inverted from dashboard
• Same relay module worked with different platform but not OceanRemote
• LED indicator on relay module shows opposite of dashboard state
• Multiple relays all behave inverted

What is Relay Logic?

Relay logic determines what voltage level on the GPIO pin activates the relay. Different relay modules use different logic types.

Positive vs Negative Logic Comparison

State	Positive Logic	Negative Logic	Your Module?
Relay ON (click)	GPIO = 3.3V	GPIO = 0V	Test with multimeter/Manual: Touch IN to GND should click if Negative; Touch IN to 5V should click if Positive. Use that to determine your module's logic. Then set dashboard accordingly. Negative: IN to GND clicks set dashboard to "Negative". Positive: IN to 5V clicks set dashboard to "Positive". If no click, check power/coil first.
Relay OFF	GPIO = 0V	GPIO = 3.3V
Dashboard "ON" button	Sends HIGH to GPIO	Sends LOW to GPIO
Dashboard "OFF" button	Sends LOW to GPIO	Sends HIGH to GPIO

If your relay clicks when dashboard shows OFF, you have the wrong logic setting.

How to Determine Your Relay Logic

Method 1: Manual Test

// Manual relay logic test:
// 1. Connect relay VCC to 5V power supply
// 2. Connect relay GND to power supply GND
// 3. Leave IN wire disconnected initially
//
// For Negative Logic :
//    Touch IN wire to GND  Relay should click ON
//    Remove from GND  Relay should click OFF
//
// For Positive Logic :
//    Touch IN wire to 5V  Relay should click ON
//    Remove from 5V  Relay should click OFF
//
// Result determines your logic type

Method 2: Multimeter Measurement

• Set multimeter to DC voltage
• Power relay module with 5V
• Measure voltage between IN pin and GND
• When dashboard shows OFF: Note voltage
• When dashboard shows ON: Note voltage
• If ON voltage is 3.3V Positive Logic
• If ON voltage is 0V Negative Logic

Method 3: Common Module Reference

• Songle Relay Module : Negative Logic
• SainSmart Relay Module: Negative Logic
• HiLetgo Relay Module: Negative Logic
• Advanced PLC relay boards: Usually Positive Logic
• Optocoupler-isolated modules: Usually Negative Logic
• If unsure: Use Method 1 above to test

Step-by-Step Fixes

1. Change Logic Setting in OceanRemote Dashboard

The fastest fix no firmware re-flash required:

• Log into OceanRemote dashboard
• Click on your device card "DETAILS" button
• Scroll to relay configuration section
• For each relay, find "Logic" setting
• Change from "Positive" to "Negative"
• Click "Save" button
• Test relay from dashboard immediately
• Relay should now behave correctly

// What happens in firmware when you change logic:
// Positive Logic:
//   if  digitalWrite;
//   else digitalWrite;
//
// Negative Logic:
//   if  digitalWrite;
//   else digitalWrite;
//
// The dashboard setting updates this behavior instantly

2. Regenerate Firmware with Correct Logic

If dashboard setting doesn't persist, regenerate firmware:

• Go to "Your Device" page in OceanRemote
• Re-enter your relay names and settings
• Select correct logic for each relay
• Click "Generate Firmware Code"
• Copy the new code
• Flash to your ESP32/ESP8266/Pico W
• Test relay operation

3. Test with Simple Blink Sketch

Verify relay works with known logic:

// Test sketch for Negative Logic 
const int relayPin = 2;

void setup() {
  pinMode;
  digitalWrite;  // Start with relay OFF
}

void loop() {
  digitalWrite;   // Relay ON
  delay;
  digitalWrite;  // Relay OFF
  delay;
}

// For Positive Logic, swap LOW/HIGH:
// digitalWrite;  // Relay ON
// digitalWrite;   // Relay OFF

4. Check Physical Relay Module Label

Some modules indicate logic on PCB:

• Look for "Active High" or "Active Low" text on PCB
• "Active High" = Positive Logic
• "Active Low" = Negative Logic
• If no label, use manual test method above

5. Verify with LED Indicator

Most relay modules have an LED near each relay:

• LED ON when relay coil is powered
• If LED ON when dashboard shows ON Logic is correct
• If LED ON when dashboard shows OFF Logic is inverted
• Change logic setting in dashboard until LED matches dashboard state

Common Relay Module Logic Types

Module Brand/Type	Logic Type	Notes
Songle	Negative Logic	Most common, tested with multimeter IN to GND clicks, LED on at LOW. Set dashboard to Negative.
SainSmart 5V relay module	Negative Logic	Common on Amazon
HiLetgo 5V relay module	Negative Logic	Common on AliExpress
Omron G5LE-14	Positive Logic	Advanced grade, less common
TCRT5000 relay module	Negative Logic	Optocoupler isolated
No-name generic	Negative Logic	Test first to confirm

Prevention Tips

• Test relay logic before final installation
• Document logic type for each relay module in your notes
• Use consistent relay modules across your project to avoid confusion
• Label relay modules with their logic type
• When buying new relays, check product description for logic type
• Save OceanRemote device configuration after setting correct logic

Related Issues

• Relay Not Clicking No sound when toggling
• Relay Clicking But No Power Click but load not powered
• Relay Stuck OFF Won't turn ON at all
• Relay Stuck ON Won't turn OFF

Frequently Asked Questions

Still having logic issues? Contact Support or return to the Troubleshooting Hub.