Aluminium Case for MySensors

[allanvbcrew]

Hi,

I've been successfully using MySensors serial gateway with several nodes (temp and humidity only so far), but woud like to bring a bit of design to these modules.
I quite like the way the Netatmo modules are finished. They would be perfect for a modern interior with the aluminium case, and I wanted to replicate them, using my already built sensors, adding a MQ-135 air quality sensor, and using an aluminium pipe as a shell.

My question is : wouldn't that case work as a Faraday cage for the wireless connection?

What would be the right things to think about during design phase? I would say :

• Thickness and size of the aluminium tube (potential impact on radio efectiveness)
• Power usage impact on battery operated sensor
• Would some specific design help (holes, plastic parts, etc.?

When I see the Netatmo or all the new brushed aluminium laptops, I'm pretty sure the impact would be limited, but maybe the material used is different than simple aluminium? Or does the way the antenna is installed inside the case will change that?

Of course, best way would be to try, but I was thinking to use your experience before buying aluminium tubes!

Thanks

[BulldogLowell]

@allanvbcrew

aluminum is paramagnetic, meaning it will become magnetic when exposed to magnetic fields. So, it can affect the transmission of radio waves.

However, it is only slightly paramagnetic, but if it is doped with certain other metals (it is common to alloy aluminum to make it easier to extrude, die-cast or otherwise form) it may affect the degree of its paramagnetic properties.

If you use aluminum, and it is very very thin, you may be able to transmit radio waves through just fine. It is probably better though to design in an elegant transition to plastic, wood or some other nonmagnetic material so your radio waves may penetrate.

shorterer answer... try it and let us know

[allanvbcrew]

@BulldogLowell
Thanks for your answer!
The first tubes I've seen are 2mm thin, and it seems quite a lot to me... I'll search more for it, but not sure to find affordable place to buy just a small piece of aluminium!
I actually didn't think about wood, but now you say it, it seems awesome! I'll definitely give it a try (even if that is probably gonna take a while as I won't be home for the next couple of weeks), and will let you know!

[Dirk_H]

If you look at the Netatmo devices you can see that they have plastic caps and a long plastic notch. I'd bet that the antenna can be found in such an area...

I dont think that a small thickness will help to let the radio signal pass. Think of that very thin µ-metal sheet covers on high frequency circuits e.g. in TV or Radio inputs (where you want to stop a radio transmission). They are built to not let radio waves pass and they are thin - so I dont think the thickness plays a major role. As Bulldog wrote paramagnetic blocks radio waves. And aluminum stays paramagnetic even if you reduce the thickness.

But I made the experience that relatively small areas, where the radio waves will not get blocked (e.g. plastic caps) can make the difference between no signal and "its working". Also keep in mind that nearly all antennas have a direction. So changing the orienation of the antenna might dramatically change the transmitting capabilties.