PippyG cases

The suggestions below are heavily based on the work of Adrian Bicker. He started developing AudioMoth cases for the Nathusius’ Pipistrelle project in 2018 on the south coast, and went on the develop a design that used hydrophobic stainless steel mesh to cover the mic hole. He has since gone on the produce over 1,000 of his design of cases for use in the BCT British Bat Survey, and for the Forestry Commission, RSPB, Stirling Uni. amongst others. Hence this is a tried, refined and well tested, design.

Adrian’s cases work on the principle of trying to be “weather proof” rather than “water-proof”. Having a totally sealed case is not a good idea, as when the air in the case is heated and expands, the only thing that can give is the vent, which is likely to bulge, then eventually pop. There are LOTs of examples of this online.

We do not suggest using any waterproof vent that is designed for voice or music speaker applications. These are designed to pass frequencies within the human hearing range, and the amount of sound they let through decreases as the frequency increases.

Click here for more details of Acoustic Vents

Open Acoustic Devices do sell spare vents for their Audiomoth cases.

For those considering using the Gore GAW334 acoustic vent sticker do have a look first at its spec. sheet:

• https://www.gore.com.cn/sites/default/files/2017-08/GORE%C2%AE%20Acoustic%20Vents_Immersion%20Application_Aug2017.pdf

Is shows the GAW334 is the worst performing of their acoustic vents, and in particular this graph of Frequency response by Frequency (note: both scales are log.) shows the response nose diving above 6kHz. The graph ends at 10kHz, heaven knows what the response is it at 110 kHz??

We’d suggest that the weather-proof cases produced by Adrian Bicker for the BCT, FC and others, using stainless steel mesh as described on this page will do a far better job, than any vent designed for voice applications.

We would love to hear your experiences or questions, please do contact us, or post a message on our Facebook Group.

Case options

1/ 3D printed case

We have not yet seen a version of this case in the hand, and while it might be OK in dry weather, we do have a few questions about:

• Edge weather proofing – it appears to rely on a push-in fit to seal the edge
• No allowance for a vent cover
• Having a hole so the Pico LED can be seen while configuring is nice, however this does look like a invitation for water to enter
• Not sure if anyone has really tested this in typical UK weather yet.
• The cost for the 3D print at $13.88, plus postage, from PCBway is high!

2/ Ready made cases

There are two designs of ready made case that make excellent starting points for conversion into a weather-proof PippyG case.

There are advantages and drawbacks to both kinds of case, see the table below

OBO Bettermann A8 – Advantages	A8 – Disadvantages	“Type F with Ears” – Advantages	F – Disadvantages
Strong enough		Stronger. We have run over this case without damage	Needs a screwdriver to open
Simple to open, just push together fit	No rubber seal, but seems watertight	Proper silicone rubber seal – Waterproof edge	The screws are REALLY easy to lose in the field
Fits all PippyG versions	Bigger case, but not by much	Smaller case	Can only take PippyG v4.x or later
	Only comes in White	Comes in Black or White
	Textured surface, needs smoothing to get good seal to mic. vent		Mic vent is near corner, requiring care when making
	Textured surface, quite hard to apply Camo tape to	Smooth surface, easy to cover top in Camo tape
Widely available from many stores, including Amazon	The mounting holes are small, limiting mounting options.	The mounting holes can be drilled much larger, allowing a variety of mounting methods.	Can be harder to find online, often out of stock on AliExpress or eBay (eps. black) Search for: “Case 83x58x33”

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