Steve avatar image
Steve asked

Cerbo GX on Raspberry pi, Physical installation of components, How to achieve it ???

Hello everyone, thank you for your welcome !!!

Let me introduce myself, I am Steve administrator of two French-speaking websites TEARDROP-QUEBEC.NET, RPRQC.COM that talk about vintage trailers and mini trailers. I am a native and live in Canada and I live on the edge of the St. Lawrence River not far from Quebec City.

I thought of you because I have small concerns with the understanding for the confuguration for example, for the installation of three water tank level sensors (fresh water, gray water, black water and propane gas) and installing cards for relays on the Victron Energie system controlled by a Raspberry Pi.

I come to you today because I want to improve my experience in our 2020 travel trailer (Riverside RV Retro 135) and install a central screen (Raspberry touchscreen) where I could see all the relevant information on the different energy levels in the battery and liquids at a glance know the recharging capacity of the solar panels and the charge controller which will be connected to an interface on my raspberry pi 3 b +. Victron VenusOS for Raspberry Pi, but quite honestly I'm quite a novice and have no idea where to start. The software is installed and is already connected in SSH on my network and seems to work because I land on the home page, but otherwise I'm not sure.

I know that (Victron Venus Os) also allows to be able to check the levels of the drinking water tanks on board, the levels of the waste water tanks (gray and black), as well as the quantities of propane gas remaining in the tanks. But I have no idea how to do this and which level sensors should be used. Those which are already installed on the trailer are not reliable.

I already have in hand:
The Raspi 3 b +, and 32 GB SD card with VenusOS which is installed
The Raspberry touch screen, and its case
2 modules of 4 relays 5v,
2 DC to DC 12v to 5v 3 amp modules

I still have to buy Victron Energy parts for the solar part of the project, SmartSolar MPPT 100V / 30A charge controller and BMV-712 plus shunt, 2 VEdirect USB cables if needed, fuse blocks and fuses. And I'm probably forgetting a few other pieces. I am waiting to be certain that the project will be feasible and possible before.

I have done a lot of research on the different sensors with no real success, my main problem is knowing which protocol to use for this Victron system because it does not seem to have an analog port on the Raspi? I have to use what sort of equipment to be able to measure the levels of the water and propane tanks. And the other part of the problem, and not the least, is that these sensors must be resistant to water and the acidity of organic liquids (black water tank). Is it possible to use an ACD interface board to be able to achieve this. I received this response from the Canadian company GARNET. "Thank you for contacting us! We do have SeeLeveL display version that will communicate NMEA 2000 protocol that we offer our OEM's. This unit is not advertised to the general public due the advanced programming required. Model 709-N2K_NLP prototype manual is attached for your viewing. Pricing for this display is $ 280CDN and senders are $ 75 each. If you wish to order please contact me at this email address." 709-N2K NLP Manual_v3.0 PROTOTYPE.pdfIf sometimes there would be people who would be interested ...

For the relay module it's the same thing, how to be able to control lights? What kind of connectors do I use and how do I connect the wires to the relay modules? What cable connects to the GPIO to be able to transfer the data from the level sensors between the different Victron modules? Then comes the programming and setting of all its elements which will have to communicate with each other. Already, for the MPPT charge controller and the Victron BMV-712 battery monitor they are Bluetooth the information should flow well. You have to guess it's the other things that worry me.
The only things I have been able to find is this site which does not sell by the piece !! For £ 300.00.

Do you think you could help me bring this project to fruition ?? For me it's quite a challenge to overcome.

I don't know if it's clear enough for you to understand the main lines and I don't know if this is a big challenge for you ?? If not do not hesitate to contact me.

A big thank you to you for taking the time to read this far !!!

Please take note, I am a French uniligue and I use a translation tool to be able to communicate with you. It could be that there are words or baths which will not be comprehensible to you.

Physical installation of components, How to achieve it ???

cerbo gxRaspberry PiVEConfigure 3installationwiring diagram
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laurenceh avatar image laurenceh commented ·


you could start here. I have done this. It is going to be difficult if you only read French.

Regards laurence

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powerace avatar image powerace commented ·

Bonjour Steve,

I think what you want to achieve is not impossible. But it will ask quite a lot of effort of you depending on your level of experience. I managed to do a part of what you want and i think i can help you out with that. To get the relays to work is not that difficult. There are multiple treads here on the forum discussing how to get it done but it can be quite confusing to understand where and how to start. See here an example of 4 working relays i have in my camper van:


So 4 relays do work, i think technically 8 can also work but i don't know if there are any limits in the Victron software. Since you already have the hardware you can start with this. Here is a lot explained.

Then the ADC part. You are correct that the rpi doesn't have an analogue port. The solution is to use an additional board that provides multiple analogue inputs. Easiest is to resource a board that Victron provides drivers for by default like "Expander Pi" that i used. A lot of information can be found here. Mr. Duthie developed an interesting board with all kinds of useful ports but you have to get the board manufactured your self solder all parts on it and hope you get it to work.

Here in this screenshot you can see the actual tank readings of my camper van done via the Expander PI board.


Unfortunately the sensors in my tanks are of the resistive type and they are not accurate at all. This is a known problem for this type of sensors. As you also describe the sensors will corrode away over the years and stop working in the end. So best solution are indeed the Garnet sensors. A forum member here wrote some software to make Garnet readings available to Venus using the NMEA2000 protocol. I don't have experience with it yet but he made his software available here. So all in all i think what you want is achievable but it will take a lot of time and effort but as long as you are not in a hurry and are willing to learn it is a real nice challenging project to survive a Canadian winter ;-)

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Steve avatar image Steve powerace commented ·

Wow !!!! Thank you very much for all the information you provided to me, I appreciate it so much.

I'm going to take a look at all this and I will probably get back to you with a few questions. Thank you 1000 times.

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2 Answers
ess-and-solar-solutions avatar image
ess-and-solar-solutions answered ·

Hello @Steve I was wondering whether you had a look at the modifications space where I think this question may be more at home?

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Steve avatar image
Steve answered ·

Thank you very much for your answer and the help offered Laurence !!

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