House alarm transformer humming

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surfisup1000

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#290566 20-Nov-2021 10:10

The transformer on our house alarm buzzes (has done for 10 years).

The transformer is screwed into the alarm enclosure (metal), which transfers vibration and turns the enclosure and the wall into big speakers ...

Was thinking either a new transformer that is quieter, or using rubber mounts like the ones they sometimes use in pc cases for hard drives... but even then , the screw is still attached to the wall and could transfer hum .

I don't suppose anyone has experience of this? (and incidentally what the heck is wrong with alarm installers who think it is ok for their installs to turn bedroom walls into humming speakers???).

ashtonaut

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#2816044 20-Nov-2021 10:34

Our alarm transformer also hums/buzzes. It’s in the laundry so doesn’t bother us, but you can definitely hear it when you are in the room. Some days it seems louder than others.

surfisup1000

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#2816052 20-Nov-2021 10:59

ashtonaut: Our alarm transformer also hums/buzzes. It’s in the laundry so doesn’t bother us, but you can definitely hear it when you are in the room. Some days it seems louder than others.

Yes, for some reason alarm transformers hum, I get it, 230v 50hz flowing through copper wire coil.... it vibrates at 50hz.

Just wondering if it can be dampened. Been doing a little research on this. Plenty of industrial vibration dampeners, for bigger applications. I think i could mount this on rubber pads somehow, or use some hard drive dampening rubber grommets.

larknz

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#2816092 20-Nov-2021 12:36

All transformers hum at 50Hz. Some are just louder than others. Quality of construction plays a big part in how loud the noise is.

surfisup1000

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#2816099 20-Nov-2021 13:13

larknz: All transformers hum at 50Hz. Some are just louder than others. Quality of construction plays a big part in how loud the noise is.

You say the quality of the transformer makes a difference, any recommendations? It is a standard paradox alarm transform.

Thanks in advance for any good tips.

decibel

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#2816100 20-Nov-2021 13:13

larknz: All transformers hum at 50Hz. Some are just louder than others. Quality of construction plays a big part in how loud the noise is.

Not the transformers in switch-mode power supplies.

What is the output voltage of this particular transformer ?

k1w1k1d

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#2816101 20-Nov-2021 13:17

Is the alarm unit mounted in the ceiling space?

Could you could make a bracket and hang the unit on nylon strings to isolate it?

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larknz

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#2816106 20-Nov-2021 13:31

decibel:
larknz: All transformers hum at 50Hz. Some are just louder than others. Quality of construction plays a big part in how loud the noise is.

Not the transformers in switch-mode power supplies.

What is the output voltage of this particular transformer ?

The transformer will still be vibrating, it's just that the frequency will be too high to hear.

surfisup1000

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#2816107 20-Nov-2021 13:41

decibel:

larknz: All transformers hum at 50Hz. Some are just louder than others. Quality of construction plays a big part in how loud the noise is.

Not the transformers in switch-mode power supplies.

What is the output voltage of this particular transformer ?

16v... i was wondering if i could use this...

https://www.jaycar.co.nz/16vac-1-25a-unregulated-power-supply-bareends/p/MP3021

surfisup1000

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#2816109 20-Nov-2021 13:42

k1w1k1d:

Is the alarm unit mounted in the ceiling space?

Could you could make a bracket and hang the unit on nylon strings to isolate it?

Haha, probably not. The alarm panel is encased in a thick metal enclosure and secured shut, I guess to stop crims from smashing it with a hammer?

SATTV

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#2816114 20-Nov-2021 14:11

surfisup1000:

16v... i was wondering if i could use this...

https://www.jaycar.co.nz/16vac-1-25a-unregulated-power-supply-bareends/p/MP3021

As long as your alarm does not need more than 1.25A then yes that will work.

John

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SATTV

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#2816116 20-Nov-2021 14:12

It is a great number of years since I have had to do this but depending on the transformer you may be able to put a sheet or two of slim cardboard between the windings and the ferrite.

Another trick we used to do was add some superglue but you would want to have the mains turn off for that one, not a permanent fix.

If you have the space and the ability replace with a toroidal transformer, they don't hum like an E I transformer.

This will probably do the trick,

https://www.jaycar.co.nz/15v-0-15v-20va-toroidal-transformer-low-profile/p/MT2086?pos=2&queryId=1cf099cb6e64d785c24fd9893bcbfd16&sort=relevance

Or this with a bot more power.

https://nz.element14.com/multicomp/vtx-146-050-115/transformer-50va-2-x-15v/dp/1675058?st=toryoidal

Yes I know these are 15Vac and not 16Vac but it will not make a difference as the first thing the alarm panel will do is rectify it to DC the put it through voltage regulators to get the correct voltage

John

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surfisup1000

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#2816122 20-Nov-2021 14:22

SATTV:

It is a great number of years since I have had to do this

Brilliant, thanks so much for the tips.

neb

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#2816294 20-Nov-2021 20:21

surfisup1000:
Was thinking either a new transformer that is quieter, or using rubber mounts like the ones they sometimes use in pc cases for hard drives... but even then , the screw is still attached to the wall and could transfer hum .

You can get varnish/enamel-impregnated transformers that have little to no hum, they used to be common in things like bedside clock radios, not sure how easy they are to find now.

neb

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#2816295 20-Nov-2021 20:22

decibel:
larknz: All transformers hum at 50Hz. Some are just louder than others. Quality of construction plays a big part in how loud the noise is.

Not the transformers in switch-mode power supplies.

No, they whine rather than hum.

compound

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#2816301 20-Nov-2021 21:11

Standard transformer cores are made from laminated steel sheets and the small gaps between the sheets is where a lot of the audible hum comes from. Superior clamping of the core and or quality of varnishing can reduce the vibration and therefore noise. Toroids are often made from powdered materials and therefore by their design are much more likely to have less noise from magnetostriction. High frequency transformers are less likely to be as noisy because they are normally toroidal and higher frequencies have more attenuation over distance than low ones.