The effects of Electrolysis in water and how to minimize this effect?

Using Arduino General Electronics
#1

Hi all,

I need to build a sensor to see the water level in a tank that have plants(hidroponics). I don't want to use an Arduino for this sensor project. I just need to flash a led when the wires are not any more in contact with the water. This is possible to do without an Arduino?

I have this cheap sensor in mind:

1 - I will incur in problems with Electrolysis and plants(I know that this is not an electronics question. If you don't know, please ignore this question)

2 - How can I minimize the Electrolysis effect in the wires to not dissolve the wires?

Best Regards,

#2

You need to reverse the polarity on the detection wires periodically (several times per second ?) In effect you apply AC to the detection wires. This can be achieved in a DC circuit by setting one probe to 1/2 the supply voltage then switching the other probe between supply voltage and ground.

#3

Sounds like a job for a pressure switch or float switch to me. If you simply want to replace the water that is evaporated you don't need electronics. Think 'toilet'.

#4

jackrae: You need to reverse the polarity on the detection wires periodically (several times per second ?) In effect you apply AC to the detection wires. This can be achieved in a DC circuit by setting one probe to 1/2 the supply voltage then switching the other probe between supply voltage and ground.

Hi. Thanks for the reply. Do you have some schematic of this or can help me to find one similar?

Best Regards,

#5

outofoptions: Sounds like a job for a pressure switch or float switch to me. If you simply want to replace the water that is evaporated you don't need electronics. Think 'toilet'.

Hi, thanks for the reply.

I know there is much better options. But I need a very very cheap one.

#6

vices:

outofoptions: Sounds like a job for a pressure switch or float switch to me. If you simply want to replace the water that is evaporated you don't need electronics. Think 'toilet'.

Hi, thanks for the reply.

I know there is much better options. But I need a very very cheap one.

A float valve at about £7.50, or less, in the UK (approximately $12) is surely cheaper than using an Arduino?

#7

tack:

vices:

outofoptions: Sounds like a job for a pressure switch or float switch to me. If you simply want to replace the water that is evaporated you don't need electronics. Think 'toilet'.

Hi, thanks for the reply.

I know there is much better options. But I need a very very cheap one.

A float valve at about £7.50, or less, in the UK (approximately $12) is surely cheaper than using an Arduino?

Hi tack. My idea is to do that kind of circuit without using an Arduino.

#8

I remember from a long time ago, at school there was an experiment to create oxygen and hydrogen. A piece of carbon was used, but i forgot why. So maybe you can have a try at this: Use pencil refill, connect your wires to that and put the pencil refill in the water. Test it before you use it in the actual situation, to see what the pencil does.

#9

MAS3: A piece of carbon was used, but i forgot why.

Because when you use a metal anode you will slowly dissolve the anode. Think of electroplating. But graphite won't oxidize to anything soluble and your graphite rod is not going to corrode away as you apply current.

#10

Stainless steel might be good for electrodes. Dollar stores often have stainless cooking utensils that might be used for a stainless source.

#11

Use a really low voltage?

#12

@Delta_G: That's what i guessed and why i told about it. So using the graphite could be an answer to question 2. But you need to consider the resistance of that pencil refill.

#13

If you use a low voltage you won't trigger most electrochemical reactions - it takes several volts to split water efficiently, so something like 0.1V AC would really cut down unwanted electrolysis.

Unfortunately the resistivity of fresh water varies a lot depending on the amount of disolved ions (so hard and soft water differ substatially) - you might want a different electrode geometry for soft / de-ionised water to get enough current flow to be easily measurable.

Another approach would be a capacitive sensor, all water has a high dielectric constant (about 80) and this would be a non-contact method not dependent on the water's resistivity nearly so much. There are simple capacitive circuits where one of the electrodes is connected to an analog input, and grounded via a very high value resistor (100M say).

You set the pin as output, set it HIGH, then switch back to an input and time how long it takes for the charge to leak away (you can try analogRead() or digitalRead() - for a simple on-off sensor the latter would be adequate). The more capacitance on the pin the slower the charge will leak away (because there was more charge to start with). A second grounded insulated electrode forms the other capacitor plate.

#14

We have an other thread talk about water level measurement;-

The method is discussed at thread:

Ultrasound Pressure sensor X band Proximity Sensor Ku band Proximity Sensor K band Proximity Sensor Sound 315MHz/433MHz rf-link Arduino (radio waves blocked by water) Bluetooth Proximity Sensor VLF radio waves (3–30 kHz) (radio waves through by water) Laser-based water level sensor Capacitance proximity sensor Resistance proximity sensor Measurement the pump discharge pressure (if there is pump) Float switch

http://arduino.cc/forum/index.php/topic,160378.0.html

#15

vices: I need to build a sensor to see the water level in a tank that have plants(hidroponics). I don't want to use an Arduino for this sensor project.

This one might do the trick.

SIMPLE WATER LEVEL ALARM CIRCUIT USING IC 555 TIMER

WATER LEVEL ALARM CIRCUIT

#16

A good way of doing it whilst guaranteeing no electrolysis is to use capacitance to measure the water level not resistance.

You have two probes as normal, but the probes are completely insulated. Keep them a constant distance apart, say 5mm, and measure the capacitance across the probes.

The water acts like a dielectric changing the capacitance. The changes in water level will be reflected as differences in capacitance.

Yes, an advanced circuit will be required for monitoring this - some kind of oscillator based resonance circuit maybe? Or a charge time measurement unit (CTMU) like that used for CapSense™ sensors (constant current source, couple of MOSFETs, timer and ADC or comparator).

This method is also safe to use on other fluids besides water as the probes are completely sealed and are not in direct physical contact with the measured fluid.