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Polarity Switch


cbr549

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  • 2 weeks later...

  • 2 weeks later...

What are you trying to do?

It's pretty easy to build an h-bridge with relays or a mechanical switch and virtually no electronics knowledge or soldering.

If all you need to do is reverse a motor then it's the best solution.

If you need to do something more complicated such as motor speed control, you can buy pre-assembled motor controller boards.

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Yes, it may be easy for you; unfortunately it's not for me.
I am trying to reverse polarity with frequency adjustment.
I don't even know if this can be done or what is evolved but check the attached picture for reference. The frequency range may not be achievable, again I don't know?
Thanks
???

post-48696-14279144008872_thumb.jpg

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Right now we're getting somewhere.

I was going to say, I must have been under 8 years old when I built my first h-bridge.

However I wouldn't have stood any chance of building a an h-bridge working up to 15MHz.

What are you trying to do?

How much current does the h-bridge have to supply?

Does it really have to work all the way down to 0Hz? That is a pain because it eliminates using a transformer as a gate drive solution.

I think that you might not have enough experience to accomplish this task.

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So now you want to do PWM? Why didn't you say so before?

What do you want this is for?

If all you're looking for is a motor controller you're probably better off buying one.
http://cgi.ebay.com/DC-Motor-Speed-Control-Controller-12V-100A-Reversible_W0QQitemZ140357279312QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item20adf21e50

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No no, you misunderstand, I can get a PWM which will pulse currant at frequency.
I want to change polarity at frequency also along with PWM.
If I could get components exactly like the picture above, of course with different frequency parameters, but with digital display, that would be great!
Also thanks for that link, that's neat stuff but not exactly what I need.
Thanks

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You still haven't said why.

Is it a secret?

There is no application I can think of.

A DC motor will just vibrate and overheat.

A resistive load such as a light bulb or heater will consume the same amount of power regardless of the duty cycle.

It's possible you're trying to do something the hard way.

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No, it's not a secret.
It's for some hydrogen projects, hence the PWM.
I want to change polarity of electrodes at frequency and study effect if any.
The range from ?Hz to 15MHz is for experimentation purposes.

As I did the drawings something kept eluding me, something I'm missing.
The PWM pulses current and dictates duty cycle or gate.
The Polarity Switch will change polarity at frequency which I'm sure will effect power consumption but also create other unknown effects.
So...I don't know if I'm trying this the hard way or not.
That's why I'm here.

Thanks

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Any Response?

Be patient, I don't sit at the computer 24/7!

If it's one of those rediculas run your car from water schemes then you've probably been told that it won't work many times before on other forums. In case you've not been told before: electrolysis can't be used for perpetual motion because, burning hydrogen releases less energy than what is required to split up water into hydrogen and oxygen.

If you just want to produce hydrogen gas then electrolysis is the easiest way for a hobbyist to do it.

Some people talk a load of rubbish about how liquid water supposedly has a resonant frequency which can be easily excited to increase the efficiency of hydrogen extraction. The truth is that liquid water has no strong resonance, any resonance is strongly damped by the hydrogen bonds holding each molecule to its neighbour. Gaseous water does exhibit a strong resonance but the lowest mode is way up in the microwave band at 22GHz which is almost ten times the frequency used in a microwave oven.

http://www.zyra.org.uk/microw.htm

DC is best for electrolysis not AC. The ions in the liquid move very slowly so changing the polarity at a high frequency would just cause the process to reverse itself as quickly as it's happening with no electrolysis actually occurring. If you used a duty cycle of 50% the water would just heat up due to Ohmic heating. Altering the duty cycles results in electrolysis occurring equivalent to the average current flow. For example a duty cycle of 25% with a current of 30A will perform electrolysis at the same rate as a current of 15A, if the duty cycle is increased to 75% the electrolysis will still be equivalent to 15A, it's just the average current will be in the reverse direction so the oxygen and hydrogen bubbles will exchange electrodes.

I think using a constant current source is your best bet. Pure water is also a very poor conductor because it doesn't have many mobile ions. Tap water isn't pure but it might not be ionic enough to work really well; to improve the efficiency of electrolysis you need to add a salt to increase the conductivity. You could use common salt (sodium chloride) but it would produce toxic chlorine gas and leave a nasty caustic solution behind.
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I'm not going to go trough all your flamebait, I'll give you one last chance.

I've only made a load of assumptions in the absence of any concrete information.

I still don't know what your end goal is. Why haven't you told us? Is it a secret?

You'll get more help if you had just provided this information from the very beginning.

Dad gum, what arrogance!

Slinging insults will not help your cause.

I might have seemed to be arrogant but I can assure you it isn't the case, it's something you've assumed.I think you took my comments out of context, so what I'm probably more knowledgeable when it comes to electronics? I didn't mean to imply that I'm more knowledgeable than you full stop.  You could be twice as intelligent as me for all I know.  My point was that if you're asking someone for advice with something that you're having difficulty with then you should provide them with as much information as you can and not go on the defensive when they question your existing idea.

Do you want to do this or not?

Yes I am still willing to help you but only if you provide more information.

For the final time: what is your end goal?

I am asking this question for your own good because from what you've said, it doesn't sound like you're going the correct way of doing something.

How do I know this?

I don't really know for sure but I have this feeling because as far as I'm aware there is no real world application for a 12V 30A 0-15MHz AC PWM power supply.
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Yes I am still willing to help you but only if you provide more information.

For the final time: what is your end goal?

I am asking this question for your own good because from what you've said, it doesn't sound like you're going the correct way of doing something.

How do I know this?

I don't really know for sure but I have this feeling because as far as I'm aware there is no real world application for a 12V 30A 0-15MHz AC PWM power supply.


Please excuse the interruption.
Now back to what
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