Reverse Polarity Timed Circuit Need Help

[gunlocators]

Here is what I am wanting to do and cannot figure out how to accomplish it. I want to use 3 9v Batteries in Series and run +/- 27v in to a circuit and I want +/- 27 also out of the circuit. Heres where I am unsure. Although I know I could use a switch to manually change polarity. I am wanting a timed circuit to swap polarity. The timing is not too critical but needs to be between every 2-3 minutes to swap the polarity. Also would be nice to have a way to protect the out going 27v leads as they are going to be electrodes to have some sort of protection in case they were to touch and short out. Thats not absolutely critical but would be a nice feature. I have been stuck for 2 weeks trying to figure out how to get a circuit built that will allow for auto switching of polarity. Any help and assistance or ideas would be GREATLY appreciated.

A little more info I am building a Colloidal Silver Generator the Silver Electrodes go in distilled water. The reason for reversing polarity a time intervals and back and forth is to ensure one electrode is not eroded over time faster than the other. If some one is willing to help me complete a circuit that will work, I would be happy very appreciative.

Thank you
Rodney W3LDR
Amateur Radio Operator

 

[Misterbenn]

Firstly let me be the first to say that your output voltage will be much lower than 27V considering that the battery voltage will decrease as they discharge.

A H-bridge would be an easy way to swap the polarity of your electrodes, Google it

 

[gunlocators]

To counter that I will use the batteries for emergency use only. I guess I will have a switch one for battery power one for a wall wart providing constant power. I will look ip H Bridge Thank you....

 

[gunlocators]

Any idea how to make it timed to auto switch the h bridge looks simple enough just need the timing part to get it to swicth now

 

[Nigel Goodwin]

Any idea how to make it timed to auto switch the h bridge looks simple enough just need the timing part to get it to swicth now

As it doesn't need to be at all accurate, a simple 555 timer would do the job.

 

[gunlocators]

Any idea where I could determine capacitors and resistors needed to get the 555 to turn on a for couple minutes and stay off a couple minutes? Or can a potentiometer be used to adjust timing I never used a 555 but have read a little about them

 

[gunlocators]

Any idea where I could determine capacitors and resistors needed to get the 555 to turn on a for couple minutes and stay off a couple minutes? Or can a potentiometer be used to adjust timing I never used a 555 but have read a little about them

 

[MikeMl]

Answer the questions I asked over on AAC

 

[Misterbenn]

Just google 555 calculator there are plenty of websites

 

[KeepItSimpleStupid]

Take a look here: https://www.electro-tech-online.com/threads/reversing-polarity-for-electrolysis-project.119652/ The project was extensively done here a while ago.