PVC pipe installation

Gareth70 · January 22, 2022, 3:23am

Hi, just wondering how common the PVC pipe method is? I am installing a shake in the UK, and don’t really have a suitable concrete floor, and fixing pretty much anything to the house structure will guarantee extreme noise anyway.

My plan is to use solvent-weld end caps, and also use a potting compound over the PCB just in case moisture does get in.

My main question is whether going deeper than 1.5-2m (easy digging) produces any better results? It’s soil to 1m here, and then sand/clay for 20m+. I’m willing to auger down, but my gut feeling is that it won’t be worth it?

Stormchaser · January 23, 2022, 8:12pm

Hello Gareth70,

While waiting for other experts in the community, I will attach a link to the list of all vaults that our users have built during recent years: You searched for vault - Raspberry Shake

Naturally, as you can imagine, best results are obtained when a seismometer is placed directly on the bedrock. However, this may be impossible for many, so I would say that your idea of going around 1 to 2 meters should be fine to lower your local noise.

Gareth70 · January 28, 2022, 6:23pm

Thank. I should be able to put it in clay at 2m or so, which should be ok!

I am a few miles from some army barracks which do demolition training every month or so, which are loud enough to wake me up and shake the house, so what that looks like will be interesting!

Rather than gluing the geophone down I managed to figure out a way to clamp/brace it. Below the cross-piece are 2x M4 nuts, the screws are turned to hold it just snugly. The side pieces are glued on using solvent-weld adhesive.

I have done most of the cable extension setup, I should be able to get it running soon.

Stormchaser · January 28, 2022, 9:20pm

This looks very interesting! Great job!

Now that I am seeing your setup, remember that the cables from the geophone to the blue Shake board should not exceed 20-30 cm max, otherwise from that distance onwards the cables themselves will start to act as antennas, and pick up all sorts of spurious signals.

From the picture, it doesn’t seem that they are that long, but I wanted to give you this info before you finished your assembly, in case you have to modify something.

Gareth70 · March 12, 2022, 6:54pm

Hiya, sorry for the late response, this is project I am working on little and often

I’m using MAX232 drivers to extend the TX/RX, as suggested in the guide in the manual and putting the whole lot in the pipe, so the geophone wires will be unaltered.

I managed to finish it all and dig a shallow hole to get it set up for testing. After considering various options, I cast about 20kg of concrete in a large flowerpot, and secured a steel plate in the top with fittings to clamp down the end of the pipe, so that it is held securely against the concrete (I’m hoping this all works ok, it seems to make sense!). I filled the pipe with “Magic Gel” potting compound, so the entire thing can be pulled up and opened for repair etc. if ever required. There’s a couple of loops on the top for rope to lower it into the hole. (The rust is because I left it outside after welding…)

The Pi (a Pi 2 B I had spare) is powered from a TP Link PoE adapter, since it means it can all be powered neatly from one cable.

Stormchaser · March 14, 2022, 9:52am

Hello again Gareth70, and don’t worry, this looks like a very interesting assembly and installation!

I particularly like the external box that you have realized for the Shake, with the POE splitter all in order, together with the concrete pad in the flowerpot. Great work with the MAX232 drivers, this should ensure greater performance with your current setup!

Let us know how the testing proceeds!

Gareth70 · March 16, 2022, 3:04pm

Thanks! Yeah I wanted to keep the Pi close. The box was a pretty cheap thing from CPC/Farnell, I think it was about £7. The cable from the house is interior-grade Cat5e (I have a full reel I need to use up!) but seems to work ok.

First results are that overnight the trace is pretty flat, but during the day there’s masses of noise, likely from cars on roads nearby. I have a week off work next week, so one dry day I’m going to widen the hole to a pit I can get into, then use a post hole digger to get as far down as I can from there, and then see how it goes!

PhilipPeake · March 16, 2022, 7:49pm

Gareth - I don’t know if a deeper hole will help much, if at all. The diurnal variation in background “noise” is just a fact of life, especially in inhabited areas. I am a bit amazed at how far a lot of vibration carries.

Mine is sitting on a 30’x60’ concrete slab (barn floor). It quite happily picks up the spin-cycle of our washing machine ~30m away in the house. We are ~1 mile from a main road and 1.5 miles from the town, but there is still a marked difference between day and night:

The big signal this morning was the Japanese earthquake … but I think you can see the day/night difference. There was some building work going on about a mile away, and when the earth-moving equipment was active there it was very obvious.

When I look at some of the devices closer to big towns/cities I stop worrying about mine … I think there are really very quickly diminishing returns on whatever you do once you have it out of the house and in fairly good contact with the ground. Unless you want to move to a location far, far away from other humans (has its attractions …).