REL1101 buzzing/humming when DigitalOutput channels are opened, even with no load connected

[pkokoras]

Hello,

I am using a Phidgets REL1101 16x Isolated Solid State Relay Phidget connected to a HUB0002 VINT Hub.

I am hearing a noticeable buzzing / humming sound from the REL1101 board. At first I thought it might be caused by my Max/MSP patch or by the connected loads, but I have now done several tests and the sound seems to come from the REL1101 itself.

Here is what I tested:

- The REL1101 is connected to VINT Hub Port 3 (hub 4 slightly softer sound?).
- I disconnected all external loads from the relay outputs.
- The buzzing still happens with no load connected.
- When I close Max/MSP, the buzzing stops.
- When I open the same DigitalOutput channels in the official Phidget Control Panel, the buzzing also happens.
- In the Control Panel, the board is quiet before opening the channel.
- When I open an on/off relay output channel, the board starts buzzing.
- When I use the PWM slider in the Control Panel, it produces a very similar buzzing sound.
- I originally used channels 0, 1, 2, 3, then changed to channels 10, 11, 12, 13, but the buzzing continues.

So it does not seem to be caused by the load or by my Max patch. It seems related to opening/activating the DigitalOutput channels on the REL1101 itself.

Is it normal for the REL1101 board itself to make an audible buzzing/humming sound when DigitalOutput channels are opened, even with no load connected?

Thank you for any advice.

[burley]

How loud are we talking? There is definitely some coil whine from the inductor used in the isolation. It's there as soon as you plug the board in, though the pitch does tend to change a bit when the board is active so it might be more noticeable.

It's very quiet though. I can't hear it unless the board is very close to my ear (<6"). I can't detect any measurable noise beyond ambient in a quiet office with an SND1000 even right up next to the inductor. Unless your environment is unusually quiet I wouldn't expect it to make any discernable noise.