Uplight dimmer based on phase-fired controller: Noise Issue

[stenzer]

Hi,

can anyone give me an advice how to get rid of the annoying sound of a phase-fired controlled uplight?

The dimmer has the number HY-3360C. I already disassembled the circuitry. Below you can find a picture of the dimmer, the schematic and a Spice simulation.







I'm very thankfull for any tip, the noise drives me nuts :-?.

greets

 

[betwixt]

By 'noise' do you mean the acoustic buzzing you can hear from the unit or the interference it causes on nearby radio equipment?

The buzzing sound it might make is from the rapid increase and decrease in magnetic field in the inductor as the triac fires. They physically 'shake' due to slack in the wires and it is that you hear. As the inductor should run cool, the best solution is to pot it in epoxy resin to hold it all together tightly.

Brian.

 

[kdolvich]

with the phase-angle control it is possible to reduce noise if begin feeding with the begin of half wave to some angle, not from some angle to end of halfwave.
such type of angle control can provide dimmer based on HV mosfet.

 

[stenzer]

Hi Brian,

By 'noise' do you mean the acoustic buzzing you can hear from the unit or the interference it causes on nearby radio equipment?

No, the buzzing is caused by the dimmer itself. No other electrical device is included.

The buzzing sound it might make is from the rapid increase and decrease in magnetic field in the inductor as the triac fires. They physically 'shake' due to slack in the wires and it is that you hear. As the inductor should run cool, the best solution is to pot it in epoxy resin to hold it all together tightly.

Interesting, never thought about that. So I should fill up the inductur shown in the first picture with epxoy resin?! Can you recommend a suitable one? As you mentioned the inductor should run cool, I'm curious about the thermal properties of the resin.

greets

- - - Updated - - -

Hi kdolvich,

with the phase-angle control it is possible to reduce noise if begin feeding with the begin of half wave to some angle, not from some angle to end of halfwave.
such type of angle control can provide dimmer based on HV mosfet.

thank you for your input, but if it is possible I want to fix the existing circuitry instead of replacing it. If I'm not able to get rid of the noise for the shown dimmer, I will consider your suggested approach.

Thanks!

 

[betwixt]

Interesting, never thought about that. So I should fill up the inductur shown in the first picture with epxoy resin?! Can you recommend a suitable one? As you mentioned the inductor should run cool, I'm curious about the thermal properties of the resin.

I'm not sure where in the World you are so I don't know what may be available locally. In the UK, I would suggest "Araldite" but I'm sure the same stuff is available under different names elsewhere. It is a two part (two tubes) epoxy resin, you mix equal amounts from the tubes, give it a quick stir then flood the inductor with it. When it sets you have a solid block with the inductor completely encased. It is important that the resin flows around and between the turns on the core so any air gaps are filled.

Many commercially available filter inductors are already 'potted' in resin but I doubt you would find one that would be a drop-in replacement for the one you have.

Brian.

 

[KlausST]

Hi,

If you want to find the source of the sound you could use an isolated stethoscope.
If you don't have then a small tube could work. One end close to the ear, with the other end scan your circuit.

Klaus

 

[stenzer]

Hi Brian,

Thank you for the suggested epoxy. All two component epoxies I used so far are not really liquid when they are mixed, they are pretty high viscous (like cold honey).

greets

- - - Updated - - -

Hi Klaus,

Hi,

If you want to find the source of the sound you could use an isolated stethoscope.
If you don't have then a small tube could work. One end close to the ear, with the other end scan your circuit.

Klaus

thank you, I never would have thought of investigating the circuitry by a stethoscope :lol:. Unfortunatly the noise is really loud. It can be heard from ~5 meters.

greets

 

[betwixt]

As long as you temporarily build a barrier around the inductor (or remove it from the board first) the viscous epoxy should work. Don't use anything that sets in 5 minutes, a slower setting type will allow enough time for the thick resin to find its way into all the gaps. If you can, wrap some tape (3M or similar) around the outside first to build a dam, preventing the resin flowing where you don't want it.

Brian.

 

[Easy peasy]

"SCR talk" is also a feature of large SCR installations due to the rise time of current in the devices

potting with "araldite" or similar 2 part potting goo or transformer varnish may well help with the sound - but you will also hear it in the filament of the bulb ( in a quiet ambient ) - the only way around this is a large series choke to limit the rise time of the current ....

 

[KlausST]

Hi,

Unfortunatly the noise is really loud. It can be heard from ~5 meters.

The point with the tube is not the loudness..it's to locate the part that generates the noise.
In an SMPS often some noise is generated by ceramics capacitors (due to their piezo effect).
With the tube you can find out which capacitor has to be replaced (maybe with a foil type).

Klaus

 

[stenzer]

"SCR talk" is also a feature of large SCR installations due to the rise time of current in the devices

potting with "araldite" or similar 2 part potting goo or transformer varnish may well help with the sound - but you will also hear it in the filament of the bulb ( in a quiet ambient ) - the only way around this is a large series choke to limit the rise time of the current ....

Unfortunately there is not a lot of space left to place an additional a large choke, maybe between the terminal block, the fuse and the potentiometer as there is also an corresponding printing on the board. But there are no associated solder pads on the bottom side.

Hi,

The point with the tube is not the loudness..it's to locate the part that generates the noise.
In an SMPS often some noise is generated by ceramics capacitors (due to their piezo effect).
With the tube you can find out which capacitor has to be replaced (maybe with a foil type).

Klaus

Ok, I thought the large noise would make it impossble to locate the spot. I will give it a try!

greets

 

[ZASto]

Just pot the existing choke in epoxy resin, preferably a variety that does not harden in minutes but in hours.

 

[stenzer]

Hi,

I searched for an epoxy resin which is processable for a longer time and which is available at my local DIY store.
I came up with this one [1], which is processable for 90 minutes and is rated for temperatures up to 100 °C.

Is there anything that speaks against my choice?

[1] https://www.uhu.com/en/product-page/plus-endfest/3950

greets

 

[KlausST]

Hi,

UHU Endfest becomes very hard, almost no elasticity.
For electronics I usually use some potting with at least a bit of end elasiticity to keep force caused by thermal stress low.

In an electronics store you should find suitable potting for electronics.

Klaus

 

[betwixt]

Search for 'potting compound' but the UHU resin should be OK. I very much doubt the inductor temperature would rise significantly in that application unless you were controlling very high power (several hundred Watts) lighting.

Brian.

 

[stenzer]

Hi Klaus,

Hi,

UHU Endfest becomes very hard, almost no elasticity.
For electronics I usually use some potting with at least a bit of end elasiticity to keep force caused by thermal stress low.

In an electronics store you should find suitable potting for electronics.

Klaus

it is pretty hard to choose an epoxy resin based on online datasheets as I do not know how a property like "Super-strong (up to 170 kg/cm²)" influences the final epoxy condition, by menas I'm not able to imagne how it "feels" when it is cured.
Unfortunatly I have no well-assorted electronic store in my area, where I could discuss such things with the salesclerk. Maybe you can recommend an epoxy resin.

I was not able to find a long processable version of the resin (Araldite) suggested by Brian, all versions I found (on Amazon,to save shipping costs) are rapid ones (5 minutes) or also extra strong.

greets

 

[KlausST]

Hi,

Maybe you can recommend an epoxy resin.

No need to be a real shop, an online shop is O.K. as well.
No need to be an epoxy type, polyurethane for example is also good.


https://uk.farnell.com/c/chemicals-adhesives/potting-compounds

There are many other online shops, distributors ....

Klaus

 

[Easy peasy]

your: www.uhu.com/en/product-page/plus-endfest/3950

is worth a try - get plenty on - esp around all the wires .... on the core ... heat the whole thing to 35 deg C to aid the flow of the goo into all the spaces ....

 

[stenzer]

Hi,

finally I potted the inductor as can be seen in the attached, unfortunately now the noise is even louder .

Has anyone an other idea to fix the noise issue. Otherwise I will try the approach with a series choke, as suggested by @Easy peasy in post #9.

BR

 

[Easy peasy]

Is it loudest at half sine wave trigger? and quietest at full power? the 2.68mH choke is there to limit di/dt but the 47nF cap discharges into it at Triac firing and no doubt the current rings a bit ( 14.1kHz) at half sine wave trigger.

Try putting 47 ohm ( 2W ) in series with that 47nF to limit the peak current of this snubber, but more usefully ( sound wise )
try a completely different choke or chokes instead of the 2.68mH one you have - anything from 500uH upwards - that can handle the current.

in this case a hard potting compound only helps to provide a noise path - whereas a softer glue might have attenuated the noise.