# Oscilator circuit diagram

Discussion in 'The Projects Forum' started by RodneyB, Apr 20, 2014.

1. ### RodneyB Thread Starter Active Member

Apr 28, 2012
649
14
I am wanting to make a basic oscillator for a water purifier for my grey water system.

I have 2 copper electrodes that need to change polarity every 5 minutes, I am thinking of using a 555 IC for the timing but am not sure how to change the polarity on the electrodes.

Could someone kindly assist me.

2. ### bertus Administrator

Apr 5, 2008
15,801
2,387
Hello,

Any idea about the current that flows through the electrodes?
On what powersupply do you want the circuit to work?

Bertus

3. ### DickCappels Moderator

Aug 21, 2008
2,772
669
Quick note: The reason the polarity needs to be reversed is to assure that the electrodes don't corrode. For this to work in the long term, the duty cycle must be very close to 50% for each polarity, and in light of that, an NE555 alone is not a good candidate. I suggest following it with a flip-flop to maintain the 50% duty cycle.

That's all for now.

4. ### RodneyB Thread Starter Active Member

Apr 28, 2012
649
14
Thank you very much for the information thus far. Understanding the advice on the duty cycle I will use a PIC10F200 for the timing. This is very experimental at the moment and from my understanding the current going to the electrodes is determined by the volume of water. At this stage I am going to build a 12 volt 1 Amp power supply.

5. ### bertus Administrator

Apr 5, 2008
15,801
2,387
Hello,

When you are using a PIC for the frequency generation, you could use a L298 as amplifier for the electrodes.
The two inputs need to be opposite of each other the reverse the voltage.
See figure 6 in the attached datasheet.

Bertus

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6. ### RodneyB Thread Starter Active Member

Apr 28, 2012
649
14
I have just had a look at the suppliers web site where we get components from, its going to cost about US\$20.00 to import into Zimbabwe the L298. Is it possible to get the pic to switch between the electrodes. I could get it to turn on and off a relay every 5 minutes But would like to use either transistors or mosfets if possible