Author Topic: water tank level measurement... what sensor to use?  (Read 21767 times)

0 Members and 1 Guest are viewing this topic.

Offline VEGETA

  • Super Contributor
  • ***
  • Posts: 1100
  • Country: jo
  • I am the cult of personality
    • Thundertronics
water tank level measurement... what sensor to use?
« on: May 11, 2013, 07:09:17 pm »
There's a new project I will work on, it's water level sensing from the residential water tank.

I want to output a percentage of available water, then do other stuff according to it. I will take care of everything else, the only thing I don't know about is what sensor to use?

the volume of the tank is 2m^3 (length=2m,width=1m,height=1m). so when I put a distance sensor to measure the height and say it's 40cm of water, this means 40% full and 60% empty, right? that's what I plan to do.

I want a cheap sensor (solution), about 30$ or so if possible (it's a simple residential device... if it's 50$, ok. but not more ^_^).

The device I'm gonna make will have more functions to do, but they depend on what current water level is.

Thanks for help.
 

Offline somlioy

  • Regular Contributor
  • *
  • Posts: 126
  • Country: no
Re: water tank level measurement... what sensor to use?
« Reply #1 on: May 11, 2013, 07:59:11 pm »
What about a ultrasonic sensor or a load cell?
« Last Edit: May 11, 2013, 08:01:53 pm by somlioy »
 

Offline IanB

  • Super Contributor
  • ***
  • Posts: 9511
  • Country: us
I'm not an EE--what am I doing here?
 

Offline croberts

  • Regular Contributor
  • *
  • Posts: 94
  • Country: us
Re: water tank level measurement... what sensor to use?
« Reply #3 on: May 11, 2013, 08:52:32 pm »
I detect the water level in a smaller tank by attaching a length of aluminum flat to the shaft of a single turn potentiometer and attaching two floats (fashioned from vitamin bottles) to the end of the aluminum flat. I used a high quality sealed potentiometer and it is still working well after more than five years. The potentiometer is connected to circuitry that generates a changing voltage level at the input of an ADC pin on a PIC microcontroller.
« Last Edit: May 11, 2013, 09:50:12 pm by croberts »
 

Offline VEGETA

  • Super Contributor
  • ***
  • Posts: 1100
  • Country: jo
  • I am the cult of personality
    • Thundertronics
Re: water tank level measurement... what sensor to use?
« Reply #4 on: May 11, 2013, 09:22:16 pm »
about ultrasonic, I found them a bit pricy. there's some people who advised me to use a magnetic float sensor (low price) but I found some on digikey that have a higher price than they said.

I saw one in the lab and it outputs 4-20mA current which is an industry standard. Now, when I want to measure the level in PIC microcontroller, I should convert this current to a voltage for the sake of ADC.

What came on my mind is to use a current transformer because it's easy to use, it gives an output voltage that have a direct relation with the current.... (this can be further studied later as it's not very much precise).

SO, what's left to me is decide what float sensor to use.

the reason I want to avoid other types of sensors is the price. I want to make the device using cheap materials.

My project is like the following:

- a sensor to sense water level, with current transformer (or any other mean).
- PIC16F877A microcontroller.
- MOC3062M with BT139 TRIAC to control a single phase induction motor (for residential use).
- LCD to output some readings.
- few buttons to change some threshold values.


Threshold values: it's when the motor should start, say when water level is 50%, the motor should automatically start. when it's 95% it should stop... these are the thresholds ^_^. some buttons (or similar things) are used to adjust these as necessary.

Now, with that said, I think it's all clear what I wanna do. So, do you recommend a float magnetic sensor? If you recommend other types of float/level sensors it's OK to me, but the price should be cheap enough just like these magnetic ones.

Sorry for the long post... ^_____________^
 

Offline Chet T16

  • Frequent Contributor
  • **
  • Posts: 522
  • Country: ie
    • Retro-Renault
Re: water tank level measurement... what sensor to use?
« Reply #5 on: May 11, 2013, 09:33:28 pm »
I put an ultrasonic sensor in our oil tank recently, you can read about it on my blog here: http://www.chet.ie/?p=204







Chet
Paid Electron Wrestler
 

Offline XynxNet

  • Regular Contributor
  • *
  • Posts: 183
  • Country: de
Re: water tank level measurement... what sensor to use?
« Reply #6 on: May 11, 2013, 09:35:02 pm »
You could use a pressure sensor.
 

Offline Zad

  • Super Contributor
  • ***
  • Posts: 1013
  • Country: gb
    • Digital Wizardry, Analogue Alchemy, Software Sorcery
Re: water tank level measurement... what sensor to use?
« Reply #7 on: May 11, 2013, 09:45:07 pm »
Is it a plastic tank? If so then you can use 2 wires taped to the outside of the tank. The capacitance changes as the tank fills. You use it as the capacitance in an RC oscillator circuit, and use the micro to measure the frequency.

Offline IanB

  • Super Contributor
  • ***
  • Posts: 9511
  • Country: us
Re: water tank level measurement... what sensor to use?
« Reply #8 on: May 11, 2013, 09:45:52 pm »
I saw one in the lab and it outputs 4-20mA current which is an industry standard. Now, when I want to measure the level in PIC microcontroller, I should convert this current to a voltage for the sake of ADC.

What came on my mind is to use a current transformer because it's easy to use, it gives an output voltage that have a direct relation with the current.... (this can be further studied later as it's not very much precise).

Transformers work with AC, but a 4-20 mA instrumentation signal is DC.

The way you convert a 4-20 mA signal into a measurable voltage is to pass it through a resistor. For example, a 250 ohm resistor will give you a signal of 1-5 V.
I'm not an EE--what am I doing here?
 

Offline pickle9000

  • Super Contributor
  • ***
  • Posts: 2132
  • Country: ca
Re: water tank level measurement... what sensor to use?
« Reply #9 on: May 11, 2013, 09:51:18 pm »
A pot and float setup is very reliable. String pots are very accurate and easy to rig as well.
 

Offline VEGETA

  • Super Contributor
  • ***
  • Posts: 1100
  • Country: jo
  • I am the cult of personality
    • Thundertronics
Re: water tank level measurement... what sensor to use?
« Reply #10 on: May 11, 2013, 10:02:47 pm »
So, how much does these ultrasonic ones cost?
___
my tank is not plastic.
____

about pressure sensors, do you mean hall effect ones? how exactly can it measure distance so accurately?
 

Offline BillyD

  • Regular Contributor
  • *
  • Posts: 203
  • Country: ie
Re: water tank level measurement... what sensor to use?
« Reply #11 on: May 11, 2013, 10:19:06 pm »
I put an ultrasonic sensor in our oil tank recently, you can read about it on my blog here: http://www.chet.ie/?p=204


Very nice work. And in fact theft from oil tanks is becoming quite an issue these days so this could help secure the tank. Might build a similar system on ours.

 

Offline kripton2035

  • Super Contributor
  • ***
  • Posts: 1756
  • Country: fr
    • kripton2035 schematics repository
Re: water tank level measurement... what sensor to use?
« Reply #12 on: May 11, 2013, 10:23:26 pm »
So, how much does these ultrasonic ones cost?
___
my tank is not plastic.
____

about pressure sensors, do you mean hall effect ones? how exactly can it measure distance so accurately?


$2 delivered ... easy to try no ?
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=290773412333

Offline ChrisGreece52

  • Frequent Contributor
  • **
  • Posts: 780
  • Country: gr
  • Electronics Engineering Undergrad
Re: water tank level measurement... what sensor to use?
« Reply #13 on: May 12, 2013, 12:14:44 am »
A simple solution would be some transistors ... this worked for me and it is pretty simple and straight forward
 

Offline ChrisGreece52

  • Frequent Contributor
  • **
  • Posts: 780
  • Country: gr
  • Electronics Engineering Undergrad
Re: water tank level measurement... what sensor to use?
« Reply #14 on: May 12, 2013, 12:16:46 am »
So, how much does these ultrasonic ones cost?
___
my tank is not plastic.
____

about pressure sensors, do you mean hall effect ones? how exactly can it measure distance so accurately?


$2 delivered ... easy to try no ?
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=290773412333
Right they are so cheap and usefull and pretty much easy to use after you have a look at the code !!!
 

Offline ChrisGreece52

  • Frequent Contributor
  • **
  • Posts: 780
  • Country: gr
  • Electronics Engineering Undergrad
Re: water tank level measurement... what sensor to use?
« Reply #15 on: May 12, 2013, 12:17:54 am »
You could use a pressure sensor.
I may be wrong but ...... would it be accurate?
 

Offline c4757p

  • Super Contributor
  • ***
  • Posts: 7805
  • Country: us
  • adieu
Re: water tank level measurement... what sensor to use?
« Reply #16 on: May 12, 2013, 12:18:05 am »
1) Why 6V AC?
2) The capacitive method above sounds better because the levels aren't discrete. They can be adjusted without moving sensors.
3) Who taught this bastard his alphabet? "F-A-B-C D-E-Q, X-V-U-P L-M-N-O-Z!!!" Must have been some kindergarten!
No longer active here - try the IRC channel if you just can't be without me :)
 

Offline ChrisGreece52

  • Frequent Contributor
  • **
  • Posts: 780
  • Country: gr
  • Electronics Engineering Undergrad
Re: water tank level measurement... what sensor to use?
« Reply #17 on: May 12, 2013, 12:21:45 am »
1) Why 6V AC?
2) The capacitive method above sounds better because the levels aren't discrete. They can be adjusted without moving sensors.
3) Who taught this bastard his alphabet? "F-A-B-C D-E-Q, X-V-U-P L-M-N-O-Z!!!" Must have been some kindergarten!
Thats not a problem ... recenlty due to your help guys i learned that using a Smoothing Capacitor can smooth the bumpy ride :P
Also the capacitive method wouldnt request more time to build and test?
And about the third thing .... i did not got it ... its because i am sleepy... or retarted :P
 

Offline c4757p

  • Super Contributor
  • ***
  • Posts: 7805
  • Country: us
  • adieu
Re: water tank level measurement... what sensor to use?
« Reply #18 on: May 12, 2013, 12:22:59 am »
its because i am sleepy... or retarted :P

Yes.
No longer active here - try the IRC channel if you just can't be without me :)
 

Offline IanB

  • Super Contributor
  • ***
  • Posts: 9511
  • Country: us
Re: water tank level measurement... what sensor to use?
« Reply #19 on: May 12, 2013, 12:24:58 am »
A simple solution would be some transistors ... this worked for me and it is pretty simple and straight forward

That looks neat, except if that is drinking water you must be careful about what you make the electrodes out of. By placing 6 V between the electrodes you will get galvanic corrosion and some metal electrodes may release metal ions into the water. Some metals, like copper, are rather poisonous and you really don't want copper in your water supply. Make your electrodes out of something safe, like carbon or zinc.

(And I missed the obvious because I didn't expect it--but now I see 6 V AC? AC? What? That should be +6 V DC, please. Of course AC will reduce electrode corrosion, but it won't do much for the operation of the transistors.)
I'm not an EE--what am I doing here?
 

Offline IanB

  • Super Contributor
  • ***
  • Posts: 9511
  • Country: us
Re: water tank level measurement... what sensor to use?
« Reply #20 on: May 12, 2013, 12:25:45 am »
its because i am sleepy... or retarted :P

Definitely retarted  ;)
I'm not an EE--what am I doing here?
 

Offline c4757p

  • Super Contributor
  • ***
  • Posts: 7805
  • Country: us
  • adieu
Re: water tank level measurement... what sensor to use?
« Reply #21 on: May 12, 2013, 12:29:31 am »
retarted
retarted

Is that where you realize your pastry isn't quite done and stick it back into the oven, or where you return to the brothel for the second time in a day?
No longer active here - try the IRC channel if you just can't be without me :)
 

Offline ptricks

  • Frequent Contributor
  • **
  • Posts: 664
  • Country: us
Re: water tank level measurement... what sensor to use?
« Reply #22 on: May 12, 2013, 12:33:33 am »
Ir emitter and IR sensor work great and is non contact as well.
Distance from IR emitter reflection from surface gives you an analog voltage output.
I use the system on large aquariums exposed to salt and other corrosives and it works well.
If the distance is far you can use a low power 5mw laser with the beam out of focus so it illuminates a larger area.
« Last Edit: May 12, 2013, 12:35:43 am by ptricks »
 

Offline Apothus

  • Contributor
  • Posts: 43
  • Country: au
Re: water tank level measurement... what sensor to use?
« Reply #23 on: May 12, 2013, 08:49:31 am »
I remember reading about a circuit in Silicone chip several years back now where they used an air pressure sensor.

Essentially they ran a piece of pipe up from the outlet tap at the bottom of the tank towards the top, the most classic method of visually measuring a tank there ever was. However instead of leaving the top of the pipe open to the air they sealed in a pressure difference sensor. So as the tank drained the air at the top would form a small vacuum whilst when it was filled above its original high registration point it would develop a positive pressure.

If you really want more info i could try and dig it up but it is cold and wet outside and I am just not motivated for that on a Sunday.
 

Offline ChrisGreece52

  • Frequent Contributor
  • **
  • Posts: 780
  • Country: gr
  • Electronics Engineering Undergrad
Re: water tank level measurement... what sensor to use?
« Reply #24 on: May 12, 2013, 11:05:57 am »
A simple solution would be some transistors ... this worked for me and it is pretty simple and straight forward

That looks neat, except if that is drinking water you must be careful about what you make the electrodes out of. By placing 6 V between the electrodes you will get galvanic corrosion and some metal electrodes may release metal ions into the water. Some metals, like copper, are rather poisonous and you really don't want copper in your water supply. Make your electrodes out of something safe, like carbon or zinc.

(And I missed the obvious because I didn't expect it--but now I see 6 V AC? AC? What? That should be +6 V DC, please. Of course AC will reduce electrode corrosion, but it won't do much for the operation of the transistors.)
Right also he could just use a 3 volt supply and no resistors in series with the leds.That should slow down corosion
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf