Power to relay board

Question: Power to relay board.

Interesting thing happens, have a new 16 channel relay board.

When had the old 2 relay board connected I could have BOTH the USB and external power connected and everything works fine.

BUT now when the 16 channel board is connected, and BOTH USB and external power are connected ALL relay LEDs light up!(half brightness), Same if only the external power is used.

If I disconnect the external power it works fine...

Have read many many comments that indicate the both can be connected, and states that the external power is usually selected automatically.

Any suggestions? Again the 2 channel relay board works fine with BOTH USB and external power connected, lights behave "normally". ISSUE Only on the 16 channel relay board.

P.S the external power supply is the Arduino external power supply.

What is "external power", voltage and current? How is it connected to Arduino and relay board? Need complete wiring diagram, please, no Fritzing picture.

have a new 16 channel relay board

Please provide a link to your board (and a picture if possible).

Note that there are different ratings for relay coil (could be 5VDC or 12VDC) and some boards don't have the built-in power regulator installed. All boards I've seen cripple the opto isolation feature.

The external power I refer to is the Arduino wall wart, plugged into the Arduino Due.

(9V 1A Power Adapter for Arduino)

The relay board is connected via: +5; GND; and the 16 data pins.

This issue only happens with the 16 Channel relay board. NOT with a 2 channel relay board.

What I think you are getting two positive voltage at relay with respect to Arduino ground.
If I assume you have external supply of 12V then may you are getting +5v on one side and +12v on other side of relay.

The relay board is connected via: +5; GND; and the 16 data pins.

The Due's +5V pin cannot possibly supply enough current for the 16-channel relay board. Still need a link and or picture of your board so we can give better advice.

Parts:

  • Arduino Due;
  • Dr Robot 6 button display shield;
  • AM2301 Temperature / Humidity sensor;
  • 16 Channel Relay Board
  • 4 Digit Display module

AM2301: +5; GND; D22

4 Digit Display: +5;GND; D50, D51 (corrected)

16 Channel Relay Board: +5; GND; D30-D45

  • WORKS Fine when using a 2 channel relay board (D30, D32) ** With both the USB and power adapter connected.

ISSUE is only when 16 Channel relay board and BOTH USB and power adapter connected.

PHOTOS:

  1. Works fine (USB only) 1 Relay LED on - correct per pgm.
    Redirecting...

  2. ISSUE - All relay LED illuminated. (USB & Power adapter) only the one should be on.
    Redirecting...

dlloyd:
The Due's +5V pin cannot possibly supply enough current for the 16-channel relay board. Still need a link and or picture of your board so we can give better advice.

That is what I was suspecting...

Photos in new post.

There is no load on the relays - just messing with programme at the moment.

CORRECTION to my description, the 4 Digit Display is on D50, D51 - wired correctly, I just described it incorrectly in post.

You can attach pictures here if using the Reply button, not Quick Reply.

Your relay board requires a 12VDC power supply.
A link to where you purchased the product would still be helpful.

Even if properly powered an connected, the Due's outputs might not provide enough current through the opto driver curcuit for several reasons.

  • Due's outputs are 3.3V and limited to about 3mA.
  • The relay board's opto resistors might be too high to provide enough driver current at 3.3V