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Author Topic: car parking using Ultrasonic Module HC-SR04 Distance Sensor For Arduino  (Read 2401 times)
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Hi,

I'm trying to implement this but am thinking about the practical issues of having this device under rain. Will it ruin it?
I would like to put a layer of protectice material but it seems even thin saranwrap blocks the signal. What should I do?

I've also tried to modify the code obtained from a site to ignore the first few echos so we ignore the saranwrap but it seems the sound is just too attenuated by it.
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You can't seal them in and expect them to work. And much rain will break up the signal too.
Here's another one; I find they're not much good at getting echo from soft things like hair, they might not work to detect things like dogs or children.

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Brunsbüttel, SH, F.Rep.GERM
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maybe transmitter and receiver r waterproof...
so u just need to cover the board with silicone sealant...
b sure that the sealant gets good contact with the case of the transmitter and the receiver and the cables...

maybe the manufacturer can tell u, if his transmitter and receiver r waterproof...?
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-Arne

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GoForSmoke: was there a link? And indeed, testing on myself, I found the echo to be a bit unreliable. I was hoping to alter the code to ignore the echos that come in before a certain time to filter out the first 3cm but that didnt seem to work out. Also, even though its ultrasound, there was a small sound that was still audible but when covering with anything to protect it, the small audible sound was no longer perceptible. Ultrasound is much more attenuated by obstacles due to its high frequency so unless I can really crank up the power on the device, it probably wont work.

Riddick: I will try that. I know medical ultrasound transducers are waterproof. For those cases, we could also slide the transducer in a probe cover and either fill it up with water or ultrasound gel to get good contact. Will ask manufacturer and possibly try them out. They are only a few $, I wouldnt really mind if it blew up but dont want them to wear out too fast.
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No link, I got some 4-pin (5V, GND, TRIGGER, ECHO) units yesterday and got one working.

There's not only poor echo from soft (certain textures too?) things but for mine the 15 degree spread makes a difference.

The units I have have a thin metal screen in front that I think could be water/dirt soaked but you're not limited to using these units, **in theory** says the guy who hasn't made naked piezo disks work though that's what's inside the units I and most others have.

In theory you could seal the surface of a transmitter/receiver and it will work while putting a layer of wrap even a small distance beyond the surface should mess with the signal badly.

Also if you can hear it, what you hear is not the 40 kHz mine and most small units operate at. But that's not the only ultrasonic frequency used, I used to be able to hear store security and traffic signal units run at I was told around 23 kHz into the mid-70's (they're LOUD! must have driven dogs nuts!) so maybe you have lower-frequency units or you can hear amazingly high pitched sounds or your experiments caused secondary frequencies to be emitted.

I think that you can buy sealed transducers. I know that you can buy piezo disks. Making either suit your purposes isn't going to be dead simple but maybe not impossible either.

FWIW, I got these units I have with the same goal and already you've found a problem that I hadn't really thought of.


 
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The specs claim this ultrasound is 40kHz.

I've tried putting drops of water on the transducer element and at that point it just stopped working (gave me a 0 cm response). Now going from transducer to air to water to air might not be a good idea as the interface between each medium would give a pretty strong reflection with little energy going through.

I guess there are two directions I can go at this:
1- test by nearly submerging the ultrasound elements in hotglue so that the sound wouldnt have an interface when coming out and would go straight to the outside world --> this will permanently mess it up if it doesnt work

2- place the transducers deeper in the bumper so that they are more protected from rain and maybe put them in a tube to protect them from most rain direction

still no response from manufacturer
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The specs claim this ultrasound is 40kHz.

I've tried putting drops of water on the transducer element and at that point it just stopped working (gave me a 0 cm response). Now going from transducer to air to water to air might not be a good idea as the interface between each medium would give a pretty strong reflection with little energy going through.

I guess there are two directions I can go at this:
1- test by nearly submerging the ultrasound elements in hotglue so that the sound wouldnt have an interface when coming out and would go straight to the outside world --> this will permanently mess it up if it doesnt work

2- place the transducers deeper in the bumper so that they are more protected from rain and maybe put them in a tube to protect them from most rain direction

still no response from manufacturer

You should probably just use sensors designed for car bumpers as they won't be damaged by water.  You'll need to make sure you get a control circuit too as just sensors won't do anything on their own without the proper circuit and script.

Tim
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A quick google search showed
http://www.sportsimportsltd.com/parking-sensor-kit-with-display-buzzer-and-4-sensors.html
which seems to be decently priced at 99$ for 4 sensors and a display.

Was hoping to do it with really inexpensive ultrasonic sensors as bought on amazon for 6$ each (but then, LCD is 20, arduino is 30 and they wont be as reliable).
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Additional observation: the ultrasonic ranger was giving me 0 reading half the time. After sprinkling water and cleaning it off, the sensors seems to be giving reliable measurements more than 90% of the time. Perhaps it was dirty or something.
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Out behind a car when there's wet, dirt, and spray, pretty much everything gets plated over time.

Maybe have an enclosure with a sealed hatch that opens/closes itself?

LCD for feedback is a bad idea. The driver would watch that instead of looking behind!
Use audio cues instead. Faster beeps when closer, slower when farther geiger counter kind of thing.

And for sure, get at least one other kind of sensor. A PIR picks up body heat, would see animals and people that ultrasound might miss. Don't make a tool that will inspire false confidence when you might get blamed for the consequences, not when there's cars and people involved. CYA.

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I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

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