buzzing noise coming from 3d printer controller when the bed mosfet is on for awhile

[amateur_24]

So I purchased a brand new 3d printer controller. I also upgraded to the heated bed with the removable metal plate.
When I switch the bed mosfet on and the bed has gotten around 50degrees celcius, I can hear a buzzing sound coming from either the controller or the bed. I can't tell since they're close together.

What is causing this? It doesn't bother me but am curious to know whats causing this.

 

[ZipZapOuch]

As the temperature reaches its set-point, the controller starts pulsing the power to the heater to slowly ramp up and hit the target temp without going too much over. The high power (~100 watts likely) - when switched quickly is causing a buzz in an inductor (look up "magnetostriction"). At least, that's my guess. Nothing to worry about.

 

[amateur_24]

I discovered today it's not the controller board it's the power supply. They all very close to each other. Since it is in the psu and doesn't bother me anyway am going to leave it.

But just out of curiosity, let's say I tuned the frequency above the frequency range we can hear, it will then be gone right?

Hmm the pay doesn't switch very fast then

 

[picbits]

But just out of curiosity, let's say I tuned the frequency above the frequency range we can hear, it will then be gone right?

Yes but you run the risk of the power mosfet heating up as unless you can drive it hard.

 

[ZipZapOuch]

I discovered today it's not the controller board it's the power supply. They all very close to each other. Since it is in the psu and doesn't bother me anyway am going to leave it.

But just out of curiosity, let's say I tuned the frequency above the frequency range we can hear, it will then be gone right?

Hmm the pay doesn't switch very fast then

It depends. The power to the not plate may be cycling on a several second basis and the buzzing you are hearing may be coming from the 60Hz (or frequency doubled 120Hz) AC power through your power supply's transformer (or inductor).

If the hot plate is PWM controller at high (audible) frequency, then yes, it may be possible to eradicate the sound if you increase the hot plate's PWM frequency.

I have a strong feeling that the hot plate is running in a very low time constant feedback loop (seconds). How long does it buzz vs go silent? I think the buzz is the AC and the silent/buzz cycle times are the control loop for the heater.