I have managed to buy a big stash of cheap geophone sensors, they are a fairly standard vertical model 4.5Hz centre frequency with 28.8V/m/s sensitivity. I want to experiment with different multiple geophone set ups with the Shake so I’m looking for a bit of guidance on capture board parameters, wiring, etc.
Firstly, I would like to try a dual geophone setup with two sensors mounted in a single housing and wired out of phase to provide a differential (i.e. balanced) ouput for better rejection of common mode signals (electrical noise etc.) and increased sensitivity. The main reason is that I want to be able to mount the sensor away from the capture board if this is possible. I would most likely wire this back-to-back geophone arrangement to the board using two core balanced/shielded microphone cable.
Secondly, I want to try a phased array setup, with equally spaced geophones wired in series, starting with up to 10 units in a line or a square array of say 3x3 with possibly up to as many as the digitiser board can handle. This would most likely be wired using coaxial cable with suitable terminations at each geophone to allow serial connection.
I notice in the Shake shop that it is not recommended to use the RS4D with low-output geophones like mine and that the RS1D is a better choice.
- What factors dictate this recommendation?
- Is it the sensitivity of the inputs?
- If so, how many geophones can the RS1D handle, and what would the minimum number of geophones to require moving up to the RS4D?
- Does the capacitance of the input or of a connecting cable (especially a coaxial cable) have a bearing on the decision?
- What sort of total maximum cable length would be recommended for a series or differential pair setup?
I guess there are a few more practical questions to answer as well, such as how to best mitigate problems from high voltage fields from lightning, etc. but I just want to see what’s possible and which board is the best basis for further experiments. At this stage I have two RS1D’s to get started.
Great to hear from you again @jason.wood. Welcome to the Community.
You sound like a total DIYer. We welcome that!
First, in order to use that big stash of cheap geophones with your RS1D, you will need to ensure they meet spec: diy.raspberryshake.org::Hardware::Geophone Sensor, which from the sensitivity it looks like they do. Just make sure they are 380 to 400 Ohms.
re: mounting the sensor as far away from the RS1D board as possible: Cables longer than 10-20 cm are not recommended. They will act like antennas picking up all kinds of noise, even with shielded cables.
The RS1D and RS4D have identical circuits for the geophone sensors.
Generally speaking, the Raspberry Shake was not designed for what you would like to do. The ways you are looking to experiment are definitely non-standard. You can always experiment, and we encourage that, but beware that you might damage the board in the course of your experiments.
To provide a more specific analysis than this would fall under the concept of paid technical support hours. Feel free to message me off list if you would like to explore that possibility. That way we could engage with our engineers to get all of your questions answered.
I am trying to get mesh networking installed on my Shakes for integration into a wider network.
I am a long way towards a solution, using scripts and guidance from my hardware supplier, but I’m not sure I’ll be able to get it going on my own.
It involves installing a substitute driver to work under the kernel version in the supplied Shake image.
I’m still hacking away at it, but I just wanted to enquire what sort of rates I can expect if I need to engage with your software team on a paid basis?
I have replied to you directly.
Yes got the message, thanks. Will keep onto this and let you know if I need a hand. Interesting project, I hope to tell you about it sometime. That price is US dollars yes?
I have attached a Request For Quotation with some specs and a starting poitn for your software team to review.
It mainly concerns getting a suitable wifi driver onto the Shake that will work with available adapters for mesh networking with batman-adv.
An estimate will be ok if a quotation is not possible.
I have added notes about my progress so far and probably have more to offer or can provide SSH access to the device if necessary once we have engaged the team.
i will contact you directly for this, we don’t quote or provide estimates through the forum.