Weatherproof Distance Sensors ?

Anti-fog plastic just contains a form of detergent that keeps the water from beading up. Not a 100% reliable solution, and it'll wear out quickly in constant humidity. The same result can be obtained from a spray-on surface treatment, which needs to be applied often.

Certain important optically-based sensors have been known to mount a miniature mechanical wiper on the front glass for these types of situations.

Hmmm ... I used to own one of those fog-proof mirrors. The effect didn't disappear over time, no treatments were necessary. Likely the stuff was dosed with a halogen or something to alter the surface chemistry and/or charge. Maybe I could buy one and eat the aluminum backing off with HCL ...

Yea, I've considered it - but I also believe in the KISS principle and moving parts are just something else to break down (and consume power). Besides, it might *smear* instead of clean - yuk !

Ultrasonic would be perfect ... but the *cost* :-(

But where is that mirror now? How long did you have it? By quickly I meant something like a year, in almost constant humidity...a shower is going to be dry 23 hours out of 24.

And as far as ultrasonic goes, you could always glance a few threads back. ;)

$30.

Those look nice, but they're hardly weatherproof.

Mitch

Maybe this stuff is ready. From

"Foggy windows and lenses are a nuisance, and in the case of automobile windows, can pose a driving hazard. Now, MIT scientists may have found a permanent solution to the problem. The team has developed a unique polymer coating--made of silica nanoparticles--that they say can create surfaces that never fog. The transparent coating can be applied to eyeglasses, camera lenses, ski goggles ?K even bathroom mirrors, they say. The new coating was described Aug. 29 at the national meeting of the American Chemical Society."

Mitch

I'd heard about that ... but they don't exactly have tubes of the stuff down at K-Mart yet.

There was another approach, I believe using flourine gas applied to the surface of the plastic. Not really a do-it-yourself kind of thing however. Both techiques creat a hydrophobic nano-roughened surface that H2O doesn't properly 'fit' into.

They were *supposed* to have diamond coatings by now also for eyeglasses and such - created by decomposing methane and H2 at certain temperatures and pressures. Deposited thin, flat diamond 'flakes' on any surface. Might not work on plastic lenses though because the underlying substrate is STILL soft and subject to macroscopic gouges by sand and such. Kinda like putting tinfoil over jello - yea, the metal is a lot harder than the jello but you can still scoop out a chunk of the rasperry/lime right through the foil using a spoon.

Hello B1ackwater,

Please check out PSR-1 at

and let me know what you think.

As in most Sonars, there is a dead zone, which in this case (gain and pulse width dependent) can be as low as 8 inches. Current implementation provides 1" resolution, which could be reduced to perhaps 1/4 inch. Hardware supports it, but firmware would need to be changed. Can you tell me more about your requirement both technically, application wise and what the potential volume may be? We might be able to help, and would like too.

Regards,

Larry

From the title and his original post, isn't it clear that he wants a WEATHERPROOF sensor? Yours isn't and neither are other offerings in the

Providing a waterproof sensor is no problem accept packaging increases cost, size and flexibility. Putting the sensor in a plastic or metal box that fits your specific platform is the best bet. Put a couple of o-rings around the transducer and mount the sensor through a close fitting hole in the box. Then ...

Have you tried putting a latex finger-cott over the sensor head? The thin membrane will be acoustically transparent. One way I've used to protect the transducers is as follows:

1) partially inflate a balloon. 2) apply a thin film of super-glue, silicone RTV or epoxy around the side of the transducer. 3) press the balloon against the face of the transducer so that the balloon deforms over the sides of the transducer. 4) hold until adhesive cures. 5) cut away excess balloon material.

Stay dry,

Larry

There are a lot of good hermetic sealed US transducers, between $5 .. $10, see e.g. Farnell, look for "ultrasonic" or "400ET" or "400EP"

Stef Mientki

Let's just say my project needs to visit drainpipes ...

Anyway, I wasn't expecting SUB-$100 weatherproof ultrasonics, but $149.99 would have been bearable. Are you aware of anyone who has put an ultrasonic behind a very thin rubber/plastic membrane and got it to halfway work ? If it had a lot of xmit power ...

I think his offer an 'echogram' in addition to a simple distance measurement - so faster offboard hardware can do fancy stuff with the signal. Might be interesting, especially if you used a binocular sensor arrangement and some way to scan the beams around. A low-rez 3-d 'image' with exact distance easily availible ... but you'd need to be better than me with the math because it would be kinda like processing an MRI or CAT scan.

An echogram would also be cool for a robot sub - if the sensor could be seriously waterproofed that is ...