Using mmWave "RADAR" for tank level sensors?

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I’ve been working on a project that would monitor the levels in the waste tanks in our RV, and them automatically dump them when full. I started out planning on using some capacitive sensors, then went ultrasonic, but back to capacitive. Now I’m finding out that the capacitive sensors won’t work on all the tanks (not sure why). So it’s back to ultrasonic. But that would require drilling two holes in the top of the tanks. Not good.

But now I’m seeing these mmWave “RADAR” sensors from Seeed. It sounds like they may work. I’m hoping I can just place it on top of the tank, and sense the levels though the top of the plastic tank.

First of all, any comments on if this would even work? I don’t know much about the tanks, expect they are heavy plastic, not “milk jug” thin. They seem to have welds on them in places, so the plastic is meltable. The density seems to vary, I think that’s why the capacitive sensors don’t always work.

It looks like the mmWave boards use a companion ESSP32 (XAIO32) board, but I didn’t see any specifics on exactly which board works. Looking at the photo’s, the D0,-D8 pins don’t match the boards I have (ESP32-C3).

I’m guessing the boards act strictly as a I/O device, and the programming is done on the companion board? Using?? Arduino/C++?

I saw they have a Bluetooth chip, for??

There are two 24Ghz “devices” that sell for about $25, and a smaller one that sells for about $5. Not real sure what the differences are. But the programming information on the $25, seems to be “ESPHome” based?? (YAML as opposed to Arduino/C++?)

Any comments, information would certainly be welcome.

EDIT->

Ok, I found a little be more on what I was looking for, like which ESSP32 interfaces, etc… I didn’t see the next page link on the device page. I did see libraries for the device, but they are not on the Platformio platform yet, and some others are, so plenty of smooping to do there.

So any comments on viability for tank level sensing would be appreciated.

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That is odd :thinking: I use “capacitive sensing” with an ESP32-S3 on my water tanks (polyethylene ~5mm). No holes, quite accurate, long lasting.

I did try the “mmWave Radar” but it was triggered by any movement, in my case trees and animals.

I just use Home Assistant and ESPHome for the data. IF I had an RV, I’d definitely put in a Home Assistant based system :slight_smile:

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I think it’s either the material the tanks are made of (maybe metal infused or something) or the varability in the wall thickness.

A couple tanks worked OK, but other tanks, I just could not get them to sense the level change.

Disappointing too, because it took tons of work… not easy to get to.

Google AI says it (mmWave) won’t work. As you said, it triggers by any movement. Also said the tank wall would be “seen”, and nothing else, so it would return as an empty room.

So I’m not sure what the line in the data about being able to “see through plastic” actually means.

I’ve not used nor looked into HA/ESPHome very much. It sounds interesting, but I didn’t quite “get” some of the set up. Right now, I’m just coding everything from scratch using ESP’s, displays etc… I’ll have to go have another look at HA again.

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What did you use as your sensors? Did you use single point detection or strip-line?

The “touch detection” on the XIAO ESP32-S3 is quite “forgiving”… so with calibration should be able to detect through most (poly/plastic) materials.

Home Assistant is very well documented (and YouTube’d) and is certainly a lot easier to implement than a home-brew approach. The disadvantage is requiring a “Pi of sorts” to run it on… The advantage is displays are cheap (cheap tablet or direct touchscreen), the mobile app is excellent, and quite a few RV based systems are supported (Victron GX, RV-Can etc).

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I have a bunch of the Taidacent XKC-Y26 (or something like that) sensors. For some reason, they just don’t work well on that one tank. On all three tanks, I had to move them around until I found a spot that worked. That’s why I think it’s density. Frustrating too, because I got 5 of 6 sensors to work, just can’t get the high level on that one tank. If nothing else, I may try to give it another go, but it’s just so hard to gain access to that tank.

I actually thought about (still thinking) using the touch input on the ESP-32. I even bough some copper tape to use. I just haven’t tested it yet. Something else I want to try, but haven’t looked too hard at it yet, if you have any experience with it, I’d love to hear about it.

I was in more of a rush to get this one, as I’ve been working on it for about a year or so. (we only camp for about 6 months, so that’s really the only time I have to seriously work on it, and then I don’t have all of my equipment. Who else goes camping with an oscilloscope? (small, underpowered, but hey…)) But I’ve decided to slow down a bit, and work on a better sensor. I just do not want to drill holes in the tanks if I can help it.

I looked at some other sensors, I have a couple in mind, and ordered one to try out. Plus, I may try looking at the interface board on the ultrasonic sensors. I can’t believe I haven’t done that yet, but I might be able to use or modify them, so I can see the second pulse (reflected off the top level of the water). Maybe increase the power or something. Pretty sure the board/software is tuned to look at/report the first pulse.

I think what stopped me at HA, was the Pi requirement. Don’t have one, haven’t tried one yet. Just another of the many things I want to do but haven’t got to yet. It does look promising though. I do like all the options for yet, many sensors all set up and ready to go (mostly). I’ll probably go take another look, maybe look harder as the ESPhome.

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Not sure if this is the unit you are working with..

https://www.amazon.com/dp/B07FC4Z2V6

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That looks like it. They work pretty gook on the other tanks, just that one tank. I can’t get it to work at the top, on any of the accessible sides. I tried a couple of the other (same) sensors, and none of them would work, so it’s the tank somehow and not the sensors.

We have to go home for a week. So I’m going to try to do some testing with some other sensors.

Like I said, I’m in no real hurry now. I’d certainly like to have it done and over with. But I clearly need to do some more testing before I decide to drill hole in the tanks (sort of easy way out, but the tops are hard to access also, under the floor. There’s area behind a wall where I could cut into the floor, but it’s still not an easy way to go).

The ESP-32 touch sensor would be fun to play with, so I’d like to give that a shot too.

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Haven’t used any of those… seem cool.
Obviously for your use case, a sensor and some LCD of sorts is a good option - nice and simple.

The copper tape option is great for both discrete and continuous measurement. Any flat conductive material should work… I’ve used the XIAO ESP32-S3 touch sensing with flat cable, IDC cable, PCB and even a simple wire loop. Trick is “calibration” with no-fluid and fluid.

Home Assistant (on either a 'Pi or any old PC/laptop/tablet) is a fun “rabbit hole” to wander into, along with ESPHome for sensing etc. I used an HP Stream 7 (AUD120) for a customer 10 years ago and they’re still using it!

ESPHome is also fun (now that AI does all the work), but yell if you need help. I’d post code here but for some reason my posts get deleted.

Good luck with your project :slight_smile:

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That’s what I’m best at, rabbit holes…

I always did want a fully automated home. AC vents that open and close based on temp and occupancy etc… I already have the lights in the kitchen at home, above the cabinets and below, that come on when you enter. Looks great and people love it.

Thanks, I’ll take a harder look at it. I’m sure it beats what I’m doing. I’ve heard other people comment about using for their RV. (I am known for doing things the hard way)

So for now, I’ll concentrate on sensors, and HA.

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If you do decide to go down the Home Assistant rabbit hole, I’m liking the new Arduino Q as a Home Assistant controller. Much cheaper than a 'Pi, widely available, and can run directly off 12 or 24V (as well as 5V)!

“App Lab” and Arduino etc support is brilliant.

I’ll be building some support devices for it using the XIAO’s for my Off-Road rig, that may suit RV “additions” as well… (my sister is an RV “grey nomad” based in US somewhere and could do with some “smart equipment”).

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I’m pretty sure I’ll head down that hole later. But at the moment, I’m going to run with what I have working. And there’s another sensor or two (similar to the capacitive) that bid themselves as “ultrasonic”. So I’m guessing it’s more like a level sensor like the YKC, and not a “distance” type. I hope that works.

But when I do head down that hole, I would love to pick you’re brain on the HA a bit.

It does sound like a lot less work, and has many more devices available (like the Mopeka propane level sensors). I could use that, but I don’t really want to get into the low level business of trying to figure out how to communicate with them. Why re-invent the wheel over and over… right?

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No worries - happy to help :slight_smile:

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I can see the wiki page here but cannot find the product page. mmWave Radar Sensor Introduction | Seeed Studio Wiki

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I think I just looked up the part number, I remember seeing a few different manufacturers.