Onyx heated bed noise

[mlapaglia]

I am in need of some assistance, what is causing this noise? It is coming from where the wires attach to the bed. I have a Meanwell 24v psu with a crydom 50a ssr.

When I lift the aluminum heat spreader off of the bed the noise resonates with it.

[youtube]http://www.youtube.com/watch?v=akPs1OdA2vo[/youtube]

[teoman]

Very interesting indeed.

If you are still using the lcd try switching to bangbang control for the heated bed ( i remember seeing it in the lcd). Then you can see if it is the pwm frequency or something else.

[mlapaglia]

If you watch towards the end you can see the red led indicating the pwm signal sent to the SSR. When the light goes on sound is heard, different notes for different brightnesses. Also, when the bed is full on or off no sound is heard.

[teoman]

Any chance you can put a scope to it?

The other type of control should have a much lower switching frequency and should not create sound as it will be full on or full off.


I'll wait for some others to chime in before recommendin capacitors etc...

[jdurand]

Eddie currents from the PWM signal is vibrating the aluminum. Yes, aluminum is magnetic in the presence of an AC or pulsing field. Look at the rotating bit in an mechanical power meter...aluminum.

I've had large power transformers singing from multi-thousand Watt pulsed loads, have to be careful of that.

[mlapaglia]

Is this something that can hurt the bed?

[jdurand]

The vibration could wear the solder mask off the traces/heater and eventually give a short or crack. Depending on circumstances, this could be a long time or a short time.

[Nylocke]

If you clap it down it won't vibrate right?

[jdurand]

Correct, but depending on metal thickness that may or may not be easy.

[mlapaglia]

And today the noise stopped. weird...