Water invasion sensor idea

[ApproachCautiously]

@xatonic

I think @Hoho0220 's statement about using silica beads was brushed off a little too quickly. What’s the harm in throwing a bunch of them in some breathable containers in your enclosure?

You could also add in small windows of clear plastic to the enclosure and have the silica sit somewhere near it. I already have a little window on my enclosure and I’m not looking into the color change stuff because you revived the thread. It is right by my VESC so I’d say it is the perfect place to add it. Assuming I can find a listing for the stuff that isn’t 2 pounds worth of it

[b264]

@xatonic

Sidenote: you could use a DHT11 with an esp32

You could, but the ESP32 is bad at reading analog signals and it’s non-linear. (It is mostly linear)

@xatonic

really accurate readings of humidity and air temp

Not on the ESP32 without a lot of work on your part.

[b264]

@xatonic

I think @Hoho0220 's statement about using silica beads was brushed off a little too quickly. What’s the harm in throwing a bunch of them in some breathable containers in your enclosure? (Maybe even just throw in the packets if the motor controller doesn’t get too hot) I think it’d purely benefit any longboard build given it’s the mist that kills electronics. You don’t HAVE to replace them often but you could just replace them whenever you’re doing maintenance.

@Battery_Mooch

Rice (and any other substance) cannot possibly “pull out” moisture from something. There is no suction mechanism, no inhaling of air to allow extraction of moisture.

All rice (or silica gel) can do is absorb incredibly tiny amounts of water vapor that has already evaporated from the thing that is wet. Consider that carefully though…if the moisture has already evaporated from something that was wet, and that moisture is already in the air, then why go through the trouble of trying to absorb it? Just blow the moister air away.

Placing something wet in a container with rice actually slows down the drying of the item. The rice blocks any air flow, can only absorb tiny amounts of moisture (badly), and creates a high-humidity layer just outside the thing that is wet.

This higher local humidity level slows down evaporation and thereby interferes with drying. You can dry the item much, much faster by shaking out/off any excess moisture and placing in front of a fan.

The fan blows away the moisture that has evaporated and leaked out. This lowers the local humidity level, encouraging more evaporation. The fan’s air flow could also directly blow on the moisture, significantly speeding up evaporation.

If anything seems to have dried out (has anyone ever opened it up and confirmed that?) and works it has done so in spite of the rice, not because of it.

I’ve done very carefully controlled tests of this to confirm the science. Leave the thing out and grab a fan.

[frankthedragon]

Silica gel works best for maintaining humidity in a closed environment, it won’t do anything against sudden changes, which is what most cases of water ingress will be. Instead, what you’d get is the silica gel becoming saturated a week or so after installation just from pulling water vapor out of the ambient air since most enclosures aren’t airtight, and then becoming deadweight. I’ve got a 50g bag of silica gel in a midsize Peli case for camera gear, and that thing still saturates in like a month even though it’s sealed and waterproof.

[xatonic]

In a relatively sealed environment I’d think it’s beneficial to atleast reduce the relative humidity so when the temp drops after a ride it doesn’t condense on electronics? The idea came to me recently because I read that water damage often isn’t caused by a puddle inside the enclosure, rather bits of water throughout the enclosure being atomized by the vibrations (and heat?) then finding it’s way onto critical parts of electronics.

[xatonic]

Well shoot, if it’ll absorb that much in an airtight box then it might be a lost cause being used up very quickly. What about SAPs? The stuff they use in diapers, I’m unsure if it has the ability to absorb water from the air in a timely manner but it may be worth some research?

[Battery_Mooch]

@xatonic

I’m unsure if it has the ability to absorb water from the air in a timely manner but it may be worth some research?

A quick test…
Wet a paper towel and weigh it carefully. Place it in a small bowl. Then take that and the absorbent part of a diaper and place it all in a gallon zip lock bag and seal it up.

Wait a day or two and then take out the paper towel and weigh it again. If the diaper material has absorbed anything then the paper towel will weigh less.

[b264]

@xatonic

read that water damage often isn’t caused by a puddle inside the enclosure, rather bits of water throughout the enclosure being atomized by the vibrations … then finding it’s way onto critical parts of electronics

This was what all my ingress failures looked like, yes.

[DougM]

someone may have already mentioned this but wouldn’t it make more sense to put an actual water sensor in the lowest part of the battery box? They’re pretty simple, you can either make your own with a transistor and a couple of resistors or you can buy them.

None of my boards are waterproof, but they are all kind of splash proof, but I designed them in such a way that if water does get in it has a way to get back out. Now granted there will still be moisture in there, but assume that the driver and BMS boards are conformally coated that shouldn’t cause too much trouble?

So maybe it’s as simple as a weep hole?

One could even add a small fan (with a waterproof inlet) somewhere that runs after the ride for a pre-determined amount of time and blows ambient air through the compartment to eliminate any remaining moisture?

[b264]

Possibly on pneumatics, I don’t know, but I feel like there’s no way that would work on polyurethane longboard wheels, because of the spraying effect mentioned above.

[Plurf]

@ApproachCautiously

You could also add in small windows of clear plastic to the enclosure and have the silica sit somewhere near it.

alternatively you could see on the window if you get condensation

[ApproachCautiously]

True, but the little packs of the stuff will also help absorb any unwanted moisture and I have plenty of extra space in the enclosure. about 2/3 of the VESC half on the enclosure is just empty

[Battery_Mooch]

Good point but I’m wondering about their limited capacity to work. At a point, perhaps quickly for some, silica gel adsorbs (yup, that’s the word ) all it can and will do nothing after that until “recharged” in an oven.

If the bell is in paper/cloth pouches then those pouch materials can soak up moisture and hold it against something.

Unfortunately, I think the best thing to do might be what @DougM mentioned, open it up. It lets water in but also lets the water out. That’s just thinking about water though. It also lets in stuff I definitely wouldn’t want to see build up inside.

Moisture sensors might work since we want them to go off for any moisture at all instead of at a certain level or impurity content. Most “road water” should have enough stuff dissolved in it to conduct enough.

LOL…this is a tough one…no one great solution.

[ApproachCautiously]

@Battery_Mooch

will do nothing after that until “recharged” in an oven.

That is why I bought the indicating version where at 60% absorption it changes color. At that point it can still absorb more moisture, so you’d be safe to finish your ride and replace the packets once home. I also bought the versions with a porous plastic pouch so the visibility of the color is super clear.

Obviously, if any major water ingress occurs I’ll just open it up to dry everything up, but any minor amount can be handled by the silica gel. If I started a ride with them dry and I was in wet conditions and check them and find they’re suddenly saturated then that would be a pretty clear sign water got in. They change color fast with direct contact to water, and change slowly when just absorbing moisture from the air.

As it is, my enclosures are pretty water tight and I have several extra methods in place to help ensure they stay that way. The silicia gel is more of my last line of defense. They may never end up providing any significant value inside my build, and they could also just absorb small amount of moisture from my board that may or may not have ever caused any issues. I’m not expecting them to save my board from water alone. For just $9 I’m not loosing out on much to add them in.

[xatonic]

Honestly I might do something very similar… Given that my board isn’t finished and I’m still waiting on some components, I bet I could bolt on the enclosure with a teaspoon of water in the rear and some silica/SAP in the front (probably on a block so the water can’t flow directly into it). Have my friend tow me around for an hour and see the results when we get back. Anything else you’d recommend to make the test more realistic? There won’t be any heat since there’s no electronics but I don’t think it’d help atomize the water much.

[xatonic]

@DougM

So maybe it’s as simple as a weep hole?

This could simply be a little cork of sorts, when you go for a ride you put it in and whenever you get back you open it up to let everything dry out? Maybe bolt with a nylock nut inside the enclosure?

[Battery_Mooch]

@xatonic

Anything else you’d recommend to make the test more realistic?

Sounds like a great start.
The only thing to consider is whether to use “free moving” water or having it in a paper towel or cloth. Either approach is worth trying though IMO. Good luck!

[jesus]

this is a certified big brain thread