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Author Topic: Tide gauge and river water level sensor ideas  (Read 2969 times)
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in a tube with water ultrasound will have another speed of sound due to the humidity.
Furthermore the US-sensors I know go up to 1.50 meter so 4 meter is quite difficult.

Alternative is a sort of resistor-ladder that is shortened by the rising water. The higher the water the smaller the resistance.
almost any number of resistors can be used, but you need to calibrate.
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One more idea for you

Floating ball at the bottom of the tube - stainless wire tied to top of ball - goes to top of PVC tube - where there is a pulley that the wire goes over - other side of the pulley is a weight - as the ball rises the weight falls - use a hall effect sensor to measure the turns of the wheel that the wire runs over - once calibrated should give you a fairly good and consistent reading.

The hall effect sensor can be encapsulated in epoxy to protect it - wires leading to a sealed enclosure with the Arduino in it - how does that sound ?

Craig
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Think the automotive ultrasonic transducer would work best as it's waterproof, and that approach requires no moving metallic parts that will get corroded, no matter how well-sealed. Sea water is pretty invasive and corrosive.
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Float with rod

Is not practical if the rod is 4m long, it will move with wind, birds will use it and the structure of the sensor  will be more than 6m with high water, a pulley and a string don't increase the height.
I've found only expensive underwater pressure sensors , I can experiment using a cheaper one inside a jar, but I have to compensate temperature and air pressure.

IR emitter/sensor with ping pong ball.

The IR range sensors that I know work for less than 24cm, do you know any that could work with 4/5 meters?

Laser timing:

Measuring flight time seems to be hard, expensive and for some reason the cheap measurement devices are closed blackboxes that you can't hack and they are also heavy I don't know why.

Laser triangulation:

This is easier, laser diode and webcam but for 400cm I would need more than 40cm diameter in the pipe if the laser dot is around 1cm, I think the dot is less than 1cm but I have to experiment. Laser triangulation + ultrasonic could work together in the same pipe.

Ultrasonic:
is it possible to protect the sensors from humidity ? I tried different materials but none of them are transparent to the sound.

what about using some kind of encoder without a rod or pulley? ideas?

thank you very much everybody!

I located these on ebay when I was looking for ultrasonic sensors for our ROV:
http://www.ebay.com/itm/Waterproof-DC-5V-DYP-ME007Y-Ultrasonic-Sensor-Module-Measuring-Range-30cm-3-5m-/200769215193?pt=LH_DefaultDomain_0&hash=item2ebec71ad9

http://www.ebay.com/itm/Water-proof-Ultrasonic-Motion-Detector-Sensor-Module-Security-/231017085803?pt=LH_DefaultDomain_0&hash=item35c9b0fb6b

Note that they are "china waterproof".
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You could suspend a rod in a vertical tube with a force-sensitive resistor or equivalent supporting the weight. As the water level changes the bouyancy of the rod would change which will alter the load on the FSR. No moving parts, and you can make it as long as you like. You might need to clean it every few years but it should be pretty robust otherwise.
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For the price, I personally would have to give this one a try -

(Pressure/Altitude sensor)
https://www.sparkfun.com/products/11084

It claims down to 30cm accuracy (about 1 ft). I ran across a few others which claimed slightly better precision (20-25cm).

Just hook it up, attach it to a buoy....?

Maybe look into how those DIY "drones" & hobby UAVs determine location/movement/altitude. Some of it may translate surprisingly well into your application needs.

Please, let us know what you end up using....and how it works.
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For the price, I personally would have to give this one a try -

(Pressure/Altitude sensor)
https://www.sparkfun.com/products/11084

It claims down to 30cm accuracy (about 1 ft). I ran across a few others which claimed slightly better precision (20-25cm).

Just hook it up, attach it to a buoy....?

You'd need a second sensor at a fixed position so you could subtract barometric pressure, but not a bad idea if the ~25cm accuracy is enough.
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Thanks guys.

* Waterproof ultrasonic:
I've seen the waterproof sensors online and they look like the car parking sensors. I can't find waterproof ultrasonic sensors in my country nor the Maxbotix ones that look good but expensive. I can buy car parking sensors here and the complete kit is cheaper than a single Ping sensor. I wonder why. Before buying a car parking kit to hack I would need to investigate:

1) is it possible to hack it? I've found a few posts about it.  The one I can get here is hackable?

2)Accuracy and range

3) Why are they cheaper than the Ping

4) Why they have a single emitter/receiver and the Ping uses two?

Links about hacking car parking ultrasonic sensors:

http://ishankarve.blogspot.com.es/2011/06/decoding-ultrasonic-parking-sensor.html

http://www.mp3car.com/hardware-development/121995-custom-usb-parking-sensor-interface-formally-pdc-usb.html

* Weight sensor
I like this idea! I think it could  better than the pulley/float and  encoder. It uses a rod but the rod doesn't need to move 400cm up. What weight sensors do you recommend? I've an electronic scale here that I'm going to open to see how it works.

*Pressure
This is a common way to measure water depth but requires three sensors: underwater pressure, atmospheric pressure and temperature. Once you have the sensors they don't require maintenance as far as I know and they can resist weather changes better than other sensors, right?
 
*IR for 400cm
I've to investigate how well it could work I'm not sure if it is enough to increase power to increase range.

thanks again! I would love to hear more ideas!
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Hello,
As an ex-industrial instrumentation technologist, I can confirm that most open tanks to depths up to 4-metres would have used ultrasonic devices. These were very expensive, but very reliable (Pepperl & Fuchs for example). Calibration is complex. I tried cheaper versions, but they are prone to wildlife like spiders taking up residence. Floats and wires and pulleys are still widely used. Have a look at heating oil tank gauges - these seem to be cheap, contactless and wireless - probably ultrasonic. Triangulation with a couple of optical sensors is possible, and the reflective type which use a reflector like a bicycle mudguard have surprisingly long ranges (20-metres or more). I am about to do something for calculating the volume of a rainwater storage tank. I will be looking at a differential pressure sensor, but the mechanical methods might be in the running. Laser distance finders are remarkably accurate, but would need some means of damping the target movement. Also might be worth looking at how cheap digital vernier calipers work - I believe this is capacitive and again it is reliable and cheap - you could look at mechanical scaling down of your range to bring it into the caliper range. I do know that the environment agencies use float methods for bomb-proof river level measurements.
Good luck
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 @tigger: Excellent information, thank you. Could you give me more details and/or links for each sensor?

1. why do calibration is complex? Because sound speed changes with temperature or something else?

2. I didn't understand how the heating oil tank gauges work from the pictures I found

3. Triangulation with reflective surface, do you have more info ?

4. Why have you decided to use pressure or mechanical and why do you think that floats are bomb proof compared to other methods?

5. I think calibers use encoders but I would need a long rod to implement the same idea for 4m

thanks again
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Ultrasonic sensors do change with temperature and humidity because the sound waves are moving through the air and in denser air, they are slower, which is why you need to calibrate.  Of course if you are running an Arduino with multiple ADC channels, simply mount another ultrasonic sensor near the main one and have it look at a fixed target of say, 10".  From that you can derive a scale factor that tracks the variables and compensate.
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@tigger: Excellent information, thank you. Could you give me more details and/or links for each sensor?

1. why do calibration is complex? Because sound speed changes with temperature or something else?

2. I didn't understand how the heating oil tank gauges work from the pictures I found

3. Triangulation with reflective surface, do you have more info ?

4. Why have you decided to use pressure or mechanical and why do you think that floats are bomb proof compared to other methods?

5. I think calibers use encoders but I would need a long rod to implement the same idea for 4m

thanks again

All the heating oil tank sensors that I have ever seen are the float type.
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Hi,

i just did some experiments here with ultrasound distance sensor in a pvc pipe and I got the opposite behaviour, the range decrease smiley-sad So could you share a bit more information about size of the PVC pipe, diameter? Thickness of the PVC?

Or maybe it is due to the sensor, I use the HC-SR04 which I bought from dealextreme - http://dx.com/p/hc-sr04-ultrasonic-sensor-distance-measuring-module-133696

HY-SRF05 seems to be some kind of improvement of mine and not much more expensive. Anyone who has any experience on both of these?

Regarding solar powering I have some experience from a similar setup. I have built a number of wind stations(http://www.blast.nu/products) that measure both wind speed and direction and report these reading to a webservice. To power these I have tested a couple of different solarpanel solutions. It is very dependent on where you going to place the units. Here in Åre(northern Sweden) the 50W solarpanel and a 6.5 Ah lead battery is basically sufficient to power my units up to november. After that the sun is too low on the horizon so the battery wont charge. In february/march the sun is strong enough again here. So last winter we used instead old car batteries 50-60Ah which we had to manually replace every fourth week.

What you need and what is sufficient is of course very depending on how much power you draw and it is not very easy to calculate unfortunately. From experiments I have concluded my wind stations draw about 100 mA. The arduino is constantly on, the GSM unit is turned on every 5th minute and transmits the readings for the last 5 minutes and then shuts down.

/Kalle
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Hi!
Glad to now you are experimenting with the same things, hope we can keep contact and exchange experiences.

The PVC pipe has a diameter of 11cm and I'm not sure about the thickness but it's a white sewer PVC pipe, may be 3mm thick. I think narrow pipes won't work. Check if you have things insides like spider web or dirt, is the range decreased or there is some obstacle? check the angle the sensor could be detecting the wall of the pipe. I have tried with the sr05 but I'll try again with a sr04 from DX as soon as it arrive from DX. I'll test and let you know.
Interesting the information about power, what about wind power, have you tried? Check the power of the sr04 5v pin when I use the arduino connected through USB the range decreases but if I connect it to the power source it works as expected.

good luck

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A pressure sensor can also be used for this. Inexpensive pressure sensors are not made for contact with water, but that can be overcome by enclosing the sensor in an air filled container (e.g. a jar with a rubber membrane for a lid)

SubSea ROVs (remotely controlled Vehicles) fill the electronic cans with non-conducting oil. They use a special industrial oil that is purpose made but I am betting common castor oil or vegetable would work and be biodegradable if you had a leak.

  http://www.sapiensman.com/conversion_tables/electric_conversion.htm

  http://hackaday.com/2005/05/09/fully-submerged-cooling/

  http://answers.google.com/answers/threadview/id/702337.html

so:
cheap pressure sensor
long wire
two high quality baggies (one inside the other for paranoia)
a bit of castor oil
four or five tie-wraps to seal it (paranoia again)

barometric (air pressure) would be insignificant compared to the water pressure.

just though of something else: oil is less dense that water. Add a small rock in the bag.
« Last Edit: August 12, 2013, 01:13:25 am by lewtwo » Logged

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