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Best practices: buzzers inside enclosures.

Hello All,

I have a project that requires a very simple handheld interface to give warning of switched input events using light and sound. To do this I have made a very simple monostable that outputs a pulse driving two LEDs and a buzzer when an external input is received.

I have mounted the PCB inside an off the shelf hand-held plastic enclosure, with two machined holes for the LEDs and an open hole for the buzzer sound to come through. See below.

My problem is that the hole in the middle is a bit of an eyesore and you can see the circuit. It also isn't great for basic ingress protection where the final product will be used in mildly dirty/dusty environments. I would like to find some way of removing or hiding the hole to make it look more professional, while not affecting the sound output too much.

I have thought about using a graphical overlay as these can be made of thin material which could hide the hole under an opaque surface but I was wondering if anyone else has had this problem before and if there were any novel solutions they came up with?

Thank you.

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Comments

December 22, 2018 06:53

Here is one possible solution:
https://micbooster.com/microphone-holders/124-acoustic-microphone-vent.html

You can also google acoustic vents. One example result:
http://www.porellemembranes.co.uk/en/products/porelle-industrial-and-scientific/porelle-acoustic-vents/

One consideration is how harsh or wet the environment will be. W. L. Gore & Associates makes materials that block liquids but allow air to pass through. These are used for acoustic and atmospheric-pressure-equalizing vents in devices from water-resistant watches and smartphones to industrial equipment subjected to harsh environments. (http://www.gore.com/portableelectronics)

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December 24, 2018 08:19

If you are just making one or two of these, and are primarily concerned about dust rather than water under pressure, another solution could be part of a faucet aerator or aerator insert from a local hardware store. It might take a bit of hands-on examination to decide which will be best / easiest to mount, which is frequently easier to do in person at a store than ordering online. Here is an example of what I mean by faucet aerator insert: https://www.homedepot.com/p/NEOPERL-2-2-GPM-Tom-Thumb-Size-PCA-Aerator-Insert-with-Washers-97194-05/203673067

December 22, 2018 06:53

I have used LED bezels for 'neat' holes.
You could use something like this https://uk.rs-online.com/web/p/led-bezels/0577702/ with and plug the opening with some open cell foam or make a plug (LED size) consisting of a tube with some cling film stretched across the hole.

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December 22, 2018 06:53

Thanks @Boss, some good ideas there - certainly cleans up the hole a bit and provides a funnel of sorts to help the sound. The foam will definitely help the ingress if I can package it nicely.

December 20, 2018 14:57

Hi Josh, the overlay certainly 'sounds' like the obvious solution...is there a need for a certain sound level? Or sound at all, could it vibrate for instance doing away with the hole entirely?

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December 21, 2018 09:11

Hi @Ten22 I have no requirements for a specific sound level just yet, however I still need to be able to hear it with a medium amount of background noise. i.e. inside a car as it's going along. I did think about removing the hole but this can damp the sound noticeably and I can't get away with just vibration. I can play with some ideas to emulate different situations e.g. plug the hole, tape it over etc. and see how this affects the sound although I will need to read up on my acoustic theory to amplify it as best I can. :)