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How does this circuit work?

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Hi,

I have a salt chlorinator in my pool which started playing up. When I opened it up to see if I could see anything obvious I was shocked to see how little there was inside vs. how much I paid for it. Anyways to cut a long story short it had nothing to do with the unit but was a function of salt levels that were too low and the water level sensor which I remedied.

Looking at the "guts" so to speak I really want to know how it works, I am not familiar with the theory of electronics but would like to understand this apparently simple puppy.

Secondly, after about a weeks worth of operation the electrodes get gummed up with the residue of the electolosis. Obviously the Na stays behind as the Cl is released into the water. Some units automatically clean the cell, would it be possible to modify this circuit to become self cleaning?

My circuit runs of a.c., my son however has a similar unit but his supply is rectified, would would that be the trick, to reverse polarity? I would really like to take this on as a simple project to make my own self cleaning chlorinator.


Thanks
Andrew

The ammeter is used to indicate the amount of chlorine generated as it is apparently proportional to the current draw.
 

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Hi

it's just a simple circuit that injects low voltage and current in the water and the salt is seperated into chlorine and sodium, the sodium sticks on the electrodes and the chlorine stays in water.

i don't think you can do much to save it from wear... if you build your own
you can make it switch polarity every awhile so you can double the life
of the electrode.
 
What are the electrodes made out of? You could install a wiper device on the electrodes to clean them, not sure how practical that is though.
 
It's not sodium that sticks the electrodes since sodium is very reactive. The chlorine actually recombines with the sodium to reform salt shortly after it purifies the water. The scale is probably calcium from hard water which tends to collect on the electrodes. Periodically reversing the electrode polarity will reduce the buildup. (See https://wiki.answers.com/Q/Where_do...lds_up_on_the_salt_chlorinator_cell_come_from)
 
it's just a simple circuit that injects low voltage and current in the water and the salt is seperated into chlorine and sodium, the sodium sticks on the electrodes and the chlorine stays in water.

No the sodium reacts with the water producing NaOH and hydrogen gas.


The unit might have a way of aerating the water so the hydrogen reacts with the disolved oxygen to form water or it might vent it into the air in which case it needs to be operated in a well ventilated area to be safe.

I would think that all units use a rectified supply to power the electrolysis cell as AC would just cause it to get hot and wouldn't do much electrolysis.
 
Hi,

thanks for the responses.

I think I may not have been clear in my request. I more wanted to know electrically how the circuit works, (I am electronically illiterate) for example what are the SCR's is actually doing and what is it's function? Do they pulse? Why can one not just have an a.c. or d.c. supply feeding the electrodes?

By the way the electrodes do not wear out, they are coated with some fancy coating and the only way currently to clean them is to remove then carefully and to immerse them in a dilute solution of sulphuric acid. No rubbing ot toughing the electrode surface. This is a bit od a pain that is why I wanted to understand the operation of the circuit to see if the cleaning can be achieved electrically by reversing the process. It is done on the more expensive units.

Hero999, I have double checked, my sons is d.c. and mine is a.c. odd huh.


Cheers
Andrew
 
Yours is DC as well. U just don't know it. To put it in very simple terms, a SCR is basically just a diode that can be switched on with a pulse and then it switches off when the voltages going through the "diode" reverses. In your circuit the current to the electrode goes through the SCR which rectifies the AC to a very noisy DC voltage (it's a half-wave rectifier).

If U wanted to reverse the process U could duplicate the SCR circuit but with the AKs of the SCRs reversed. U could then just put a toggle switch from the transformer which will make it possible to switch between the two circuits.

Keep in mind that U can't use the same amp meter in the second SCR circuit cause the current will be in reverse so U might damage the needle

PS. This is just in theory. You'll have to test if it will work
 
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