ph and water level sensors

Development Boards MicroMod
1

Hello,

I am doing a project using PIC microcontroller…my project is to measure the ph value and water level in the aquarium and display the values on LCD…

so to measure the pha nd water level inside the aquarium, I need ph sensor and water level sensor…

I want inexpensive sensors…Can please anybody help in finding these sensors?

I will be really thankful to you for this.

2

Google?

Leon

3

Level: Use a float switch. They’re cheap, they’re crappy, they work. If you’re feeling spendy, Honeywell makes some non-contact refraction-detection sensors which are much more robust.

pH: In small quantities, look at hydroponics or aquarium stores online. Any BNC connector probe will do. You WILL need an op-amp in order to get a usable signal level out of a pH probe.

http://www.national.com/ds/LM/LMC6001.pdf

http://www.66pacific.com/ph/simplest_ph.aspx

4

Hello,

I appreciate your help and suggestions.

But I have a question regarding float switches.

Do they just tell you the water level or they just tell you if water is present or not?

Thanks

5

jassu11:
Hello,

I appreciate your help and suggestions.

But I have a question regarding float switches.

Do they just tell you the water level or they just tell you if water is present or not?

Thanks

A float switch is a float with a magnet inside, and a small reed relay in the non-moving part. They can only show approximate level.

If you want to determine actual level, you need a capacitative sensor with two conductors. I’m sure there are some projects for that on the internet.

6

So a float switch can’t tell the level values??

Suppose if i want to display the current water level onto a LCD display,

then is it possible through float switches?

Thanks

7

jassu11:
So a float switch can’t tell the level values??

Suppose if i want to display the current water level onto a LCD display,

then is it possible through float switches?

Thanks

Unless you used a float switch for every possible level in the tank, no.

A float switch is digital - water is present here or not.

Look at capacitative level sensors for ones which can sense lots of levels in between.

8

Hello theatrus,

Can you please tell me more about these capacitive sensors?

I really need these to measure the water level at various levels, at least at 4-5 points.

I went thru thsi site and found this link with capacitive sensor:

http://www.am.pepperl-fuchs.com/product … t_id=13151

Is it good for measuring water level by placing it in water?

I would really appreciate your help .

Thanks

9

jassu11:
Hello theatrus,

Can you please tell me more about these capacitive sensors?

I really need these to measure the water level at various levels, at least at 4-5 points.

I went thru thsi site and found this link with capacitive sensor:

http://www.am.pepperl-fuchs.com/product … t_id=13151

Is it good for measuring water level by placing it in water?

I would really appreciate your help .

Thanks

The sensor you found is for proximity. I have measured water level with a home made capacitor - sensor. The sensor was made with 2 strips of copper clad board, spaced a few millimeters apart with a small piece of plastic near the bottom. The strips were long enough to reach from the top of the tank to the bottom. The whole assembly was covered in shrink wrap to insulate it from the water. (Actually an ionic solution.) The sensor was then put into a 555 timer configured as an astable multi-vibrator (oscillator) as the capacitor. The frequency of the oscillator changes as the dielectric of the sensor changes from air to water. The output frequency can be read with a microcontroller capture, and you can do a look-up to indicate your level.

As for a cheap pH probe, you may get lucky and find one for under $100.

10

Try eBay for the pH probe. There are several for under $50

11

Thanks a lot for all of your suggestions and help.I really appreciate.

Can you please elaborate more on how to design capacitor sensor at home?Can you please tell me in detail what components I need to buy?

Thanks in advance.

12

You either need to design a flat plate capacitor (with insulated conductors, as the conductivity of any normal water is far too high), or a concentric cylinder capacitor (equations here: http://hyperphysics.phy-astr.gsu.edu/hb … apcyl.html - epsilon-R is about 78.5 for water at 25C, but make sure you also count in epsilon-0). You can use a stainless steel pipe and some PTFE coated wire. I’ve found the coated magnet wire often doesn’t work well, so I strongly recommend the expense of PTFE.

Tie this to a 555 timer or other oscillator circuit, which will use the changing capacitance to emit different frequencies of square waves. Use a microcontroller to capture the frequency. Calibrate the low and high point. The rest is all a linear equation if your container doesn’t have a slope.

13

Can you please put more light on the design of flat plate capacitor?

I need to buy two steel plates?and how to insulate ??

Thanks

14

jassu11:
Can you please put more light on the design of flat plate capacitor?

I need to buy two steel plates?and how to insulate ??

Thanks

The physics link above will lead you to a page on flat plate capacitors if you poke around a bit. They even give you a calculator so that you can figure out how much capacitance your design will give you. Beyond that, a quick check in the library for a AC/DC circuits book would give a lot more information as well as a technical explanation of how capacitors work.

For insulation, that’s up to your imagination. You will have to balance the materials your using against the parameters of your application. For instance, if there are any fish involved it becomes very difficult to do something like this because almost every product your going to find isn’t going to be fish friendly. I don’t recall you mentioning your exact application, so it would be very hard to give a recommendation.

15

As an alternative for level measurement is to place some kind of distance measuring device above the liquid to be measured. You can use an IR measuring device <LINK_TEXT text=“http://www.sparkfun.com/commerce/produc … cts_id=242”>http://www.sparkfun.com/commerce/product_info.php?products_id=242</LINK_TEXT> or ultrasonic <LINK_TEXT text=“http://www.sparkfun.com/commerce/produc … cts_id=639”>http://www.sparkfun.com/commerce/product_info.php?products_id=639</LINK_TEXT>

16

See article at:

http://www.zen22142.zen.co.uk/Circuits/ … ev_alm.htm

I haven’t tested it, but I hope to in the next couple of months.

17

Check out this article on a pH meter circuit:

http://www.66pacific.com/ph/ph_1.htm

All the circuit diagrams and essentials are there, I use this for my hydroponics, along with this very cheap pH probe:

http://cgi.ebay.com/PH-Probe-electrode- … 1|294%3A50

If you make a good stable source coupling voltage, say 2.5V, connect the ground of the pH probe to that, then you can hook the other side to the input of an opamp, provided it is a JFET opamp (usually megaohm input resistance, very important). I know the make controller has jfet inputs, don’t use the arduino, but it probably does too.