Reverse Polarity of Electromagnets.

geoff07

Senior Member
Rather than have us guess what you are up to, why not tell us? Then you will get far more useful advice.
 

rossko57

Senior Member
You don't get to be a millionaire by telling people what you are up to. On the other hand, you don't get what you want unless you state it clearly either. I still don't know if he wants variable rate or not.
 

erco

Senior Member
God bless the patient and helpful souls who have replied and tried to help the OP. Pity that 99% of the replies have been technically over his head, or so he claims.

Now please, it's time to let this frustrating and meandering thread die unless/until the OP spills his guts about what he's doing. There's nothing Picaxe-related in his near future here. His helpless and purposefully vague "bait & wait" attitude has consumed a surprising amount of time & talent that would have born better fruit elsewhere.
 

The Famous Cash

New Member
I greatly appreciate all the contributions and apologise for my inability to express things more clearly. (I feel the question has raised some interest amongst you experts so, hopefully, that is some good news.)

I have been thinking the best way to advance the situation and am making this last attempt to move things forward. If it makes things worse, I will back off also.

1) IF I buy two of these magnets. EL120405 from TIMSTAR, to what do I connect both of them to place them in the "on" state? They would need to able to operate for long periods of time.

2) Once having achieved the magnets to be "on", to what device (Picaxe?) would I connect to silultaneously reverse the polarity of the magnets twice a second? Again over long periods.

3) Once having achieved being able to reverse their polarity twice a second, is it just a question of adjusting the device to select other speeds of change up to (say) 50 times a second?

I have some programming skills and would probably be able to send code to a device such as picaxe. (I have a commercial program (for snooker halls) which switches lights on and off through the main computer program.)

I trust this helps and not create further confusion. I am trying to be as precise as I can
 

Goeytex

Senior Member
I'll tell you what he's up to. He' s playing us. He's exploiting the altruistic nature if those who help, expecting nothing in return. And he's exploiting the egos of others who help out of a need to demonstrate their knowledge.

As a former casino operator he under understands human nature and how to separate folks from what they have... in this case, common knowledge & information that he is too lazy to look up for himself.
 

rossko57

Senior Member
Naw that'd be silly, monopole fields are non-reversible.

Actually come up with an off the (dusty) shelf solution; purchase a vintage telephone hand-cranked bell generator from a phone collector's dealer. Crank the handle as fast or slow as you like for as long as you like.
 

westaust55

Moderator
@TFC,
A link to the Datasheet for the magnets you mention who be helpful for those who may be able to assist rather than me memorizing or cut and paste on an iPhone then Search for what you should have already located.
 

SAborn

Senior Member
Sounds to me some dodgie casino device to prevent you from winning to me, as the OP has not come clean on the device intention, and cited a lack of electronic skills to not explain the use, Bull Shirt i say! as school kids can explain their project on the furum so im sure a adult can.

We know nothing of the project, or what its for, what strength magnetic flux field is required, at what amps or what voltage, its a mere mystery.

What do we know...... The OP has run casino's, has seeked an answer to a mystery question on several forums, with giving no information about the project.

Go figure, do the math. and see what project answer you come up with, untill we are informed different.
 

The Famous Cash

New Member
I do appreciate the responses received. I do also appreciate the time many people have taken in genuinely attempting to assist me.

Certain adverse comments are creeping in and I think it only fair to address them.

I retired many years ago and it certainly has nothing to do with casino business.

I apply logic to everyday life problems and still (even after all the questions) do not see
a) The need to know WHY i am asking the question.
b) WHY no one can give an example of ANY two elctromagets and a device which will change their polarity at a controlled rate.

Now . . . If for some reason which is way beyond my comprehension, no one in history has taken two electromagnets and changed their polarity by a controlling device then I am sorry I have wasted everyone's time. I just fail to see that could be a possibility.

Again, thanks to those who are genuinely trying to help.
 

RexLan

Senior Member
I do appreciate the responses received. I do also appreciate the time many people have taken in genuinely attempting to assist me.

Certain adverse comments are creeping in and I think it only fair to address them.

I retired many years ago and it certainly has nothing to do with casino business.

I apply logic to everyday life problems and still (even after all the questions) do not see
a) The need to know WHY i am asking the question.
b) WHY no one can give an example of ANY two elctromagets and a device which will change their polarity at a controlled rate.

Now . . . If for some reason which is way beyond my comprehension, no one in history has taken two electromagnets and changed their polarity by a controlling device then I am sorry I have wasted everyone's time. I just fail to see that could be a possibility.

Again, thanks to those who are genuinely trying to help.
So to translate that you just said do it my way and give me the information I want or p--- off - good luck !

It appears that your applied logic to everyday life problems has failed you ... again.
 
Last edited by a moderator:

Dippy

Moderator
Careful with the language Rex, youngsters read this! (obv not in the rude word filter MMmmm... Technical?).


People here often reply to youngsters queries which can often be solved by alternative methods.
To do this some background is required - it may seem a bit 'nosey' but the intentions are good.

You were offered an H-bridge (or L293) suggestion and you didn't really comment other than appear to request an off-the-shelf solution (Post#10).
If you had Googled H-bridge you would have found that it could (on the face of it) be used to solve your enquiry - in conjunction with some controlling device e.g. PICAXE.

It all sounded cryptic so people's imaginations went into overdrive and you got some excitable replies - much like you did on one other Forum I looked at.

You didn't give an electrical spec on the electromagnet coil. Eclectic gave a suggestion in post#3 and you didn't even say whether it was nearly what you wanted.

If you simply want to alternate the current in a coil (or motor or transformer primary or whatever) the H-bridge technique is the simplest.
Your PICAXE code switches the legs of the H-bridge , job done.
Do a bit of Googling and see if that could be used.
 

hippy

Technical Support
Staff member
b) WHY no one can give an example of ANY two elctromagets and a device which will change their polarity at a controlled rate.
See post #5.

There appears to be no readily available device to do what you want so no one can point you to such a device.

There are plenty of ways you could possibly do what you want but your lack of electronics knowledge makes such suggestions useless to you.

Now . . . If for some reason which is way beyond my comprehension, no one in history has taken two electromagnets and changed their polarity by a controlling device then I am sorry I have wasted everyone's time. I just fail to see that could be a possibility.
I am sure many people have done what you are seeking to do but they most likely achieved that, not through taking something which exists to do it, but through having the means to obtain what is needed to do that. That likely required building the equipment themselves ( using knowledge and skills which you say you do not have ) or commissioning others to build it for them.

If there were a product you could buy off the shelf for what you want to do, could just plug it in and use it, then people here, and in the other forums you have asked in, would point you to it. There isn't such a thing that anyone you have asked is aware of, so they simply cannot.
 

Goeytex

Senior Member
I apply logic to everyday life problems and still (even after all the questions) do not see
a) The need to know WHY i am asking the question.
b) WHY no one can give an example of ANY two elctromagets and a device which will change their polarity at a controlled rate.
Speaking of logic .... Your refusal to reveal the purpose of your inquiry/experiment implies secrecy, that you do not want others to know what you are up to. Fair enough. I can think of a few of legitimate reasons for non-disclosure. But I can also think of a few not so legitimate reasons.

However, it is not unreasonable for your refusal to offer even scantest of details, (buffered with sweet talk, unnecessary apologies, and a claimed ignorance of electronics), to raise a caution flag with some folks. The fact that you have raised the ire of folks on at least two forums should give you reason to pause and consider your approach and the validity of your logic. You offer nothing in regards to purpose while wanting everything in regards to a solution from folks who don't know you and who owe you nothing. And you can't see why folks may want to know what you are up to? What kind of logic is that?

If what you posted elsewhere is factual and that you retired at the age of 31, (over 30 years ago) then it is not unreasonable to think that you are a person of means. And if a person of means then one might question (considering your claimed ignorance of electronics) why you have not hired someone experienced in electronics and electromagnetism to put something together for you. It would take no more than a day or so (with parts in hand) and is something any 2nd year EE or Physics student could do (and probably quite a few High School kids as well.) Probably get it done for less than $300. So why have you not gone this route? The only thing I can think of is that you do not trust anyone with the purpose of your experiment ... your secret.

Personally, I have the parts on hand here in my lab where I could do it in less than a day. It would take me a couple of hours to wind the magnets and another couple of hours to breadboard the H-bridge, connect a Picaxe and write the code. I am sure there are quite a few others here on this forum that could do the same or better and provide you a turn key solution. But why should I? Why should anyone?
 

SAborn

Senior Member
b) WHY no one can give an example of ANY two elctromagets and a device which will change their polarity at a controlled rate.
A stepper motor and its controller, do exactly that, its how they work.
 

RexLan

Senior Member
Careful with the language Rex, youngsters read this! (obv not in the rude word filter MMmmm... Technical?).
I am guilty as charged and ashamed of myself. I don't know what will become of me now .....

However, I am confident that these "youngsters" hear much worse from their parents ...LOL.
 

oracacle

Senior Member
You were offered an H-bridge (or L293) suggestion and you didn't really comment other than appear to request an off-the-shelf solution (Post#10).
If you had Googled H-bridge you would have found that it could (on the face of it) be used to solve your enquiry - in conjunction with some controlling device e.g. PICAXE.
would not be resonable to assume that an astable 555, not gate and h bridge could do the same job. varible resistor in R2 iirc (its been a long time since i played with 555s')
 

Dippy

Moderator
I suggested a PICAXE as this is a PICAXE forum Oracaccle.
There are various ways of controlling a bridge. Post your circuit to show us your version - it may be a start for the OP.
I haven't Googled but I suspect there may be a few different ideas.
 

oracacle

Senior Member
I will see what i can do a little later, doing a little tweaking to the macro rail software atm, but the camera battery will take a while to charge so may get a chance.
 

oracacle

Senior Member
heres something that i threw togather real quick, i have not calculated resistor and capacitor sizes and really should have pull downs on the un-used pins - most inverted come in packages of 4 so the extra will need to be tied down too, there should most likely be a some resistors between the l293, 555 and inverter but as an idea it sorta there
 

Attachments

techElder

Well-known member
How can you draw a schematic when you don't even know about power consumption or configuration of the mythical electromagnetic beast? (Not meaning to be personal.)

I've powered and repaired many electromagnets used for many different functions. It is not a trivial task considering number of turns, power, core mass, voltage and configuration to name only a few variables.
 

oracacle

Senior Member
desperation, a little thought that it may pry a little more information to derive a better idea of what would be required.

could be the the op doesnt actually have any clue about much, not just anything electrical.
I personally would thing that the l293 would be a little weak for most electromagnetic beyound low end motors and alikes
I would also hope that it would make him realise that a single device is not really an option, the 555 with an h-bridge and inverter is pretty much as simple as it going to get (cheap too).
on the other hand he may set fire to something and realise that playing with elcricity with no knowledge is a very bad idea and he should leave well alone unless he is going to give people the information that is needed to derive a full circuit from
 

AllyCat

Senior Member
IMHO the OP's specification is so vague that it's rather like saying he wants to "flash a light on and off". But that light might be a LED on a PICaxe pin or an arc lamp to illuminate a sports stadium, or perhaps a laser to create nuclear fusion. My suspicion is that he probably wants/needs the magnetic equivalent of the arc lamp, but to run off a couple of torch batteries. :confused:

As already said, the specification is basically just of a driver for a (very inefficient) bipolar stepper motor. Furthermore, virtually every electric motor on the Planet works by "reversing the direction of one or more electromagnets", either in the stator or rotor.

Cheers, Alan.
 

hippy

Technical Support
Staff member
How can you draw a schematic when you don't even know about power consumption or configuration of the mythical electromagnetic beast? (Not meaning to be personal.)
That's the art of delivering something which meets the specification provided, regardless of whether it's what the customer wants or not. Job done, hand the money over. It's for the customer to show it doesn't meet the spec or they have to accept they got what they asked for.
 

BeanieBots

Moderator
Spot on Hippy.
That said, this will meet the exact requirements.
ANY electromagnet can be driven direct from a PICAXE output providing the current limit is not exceeded. (several have been suggested already, this will drive any of them).
Put a resistor of greater 200 ohms in series and the current will be limited to a safe value.
Put a cap (any value but it must be bi-polar) in series with the resistor and the polarity will change each time the output toggles.
Then use this code:-
Code:
Do
toggle (IO pin of your choice)
Pause (a suitable value)
Loop
Fully meets all aspects of the OPs request. Job done!

So, until the OP provides any valid reason why the above is not suitable, let's not have any further pointless speculation.
 

The Famous Cash

New Member
Many thanks for all the kind responses.

There are numerous avenues I am exploring.

I appreciate some became upset due to the lack of detail which I could supply and apologise for the necessary inconvenience.

The points raised have been interesting and I understand the problem is, perhaps, not as simplistic as I perceive.

Again, thank you to all for your contributions which are being examined in close detail.
 

westaust55

Moderator
I .... still (even after all the questions) do not see
a) The need to know WHY i am asking the question.
b) WHY no one can give an example of ANY two electromagets and a device which will change their polarity at a controlled rate.

Now . . . If for some reason which is way beyond my comprehension, no one in history has taken two electromagnets and changed their polarity by a controlling device then I am sorry I have wasted everyone's time. I just fail to see that could be a possibility.
No-one can advise on what electromagents you need until we know:

1.the application. For example:
a. An electric pendulum (for a clock or metronome)
b. Lifting a steel billet with a mass several tonnes (specify weight - a safety margin then can be incorporated to engineering standards by the designer)
c. Trying to defeat/modify/adjust the operation of the 50 Hz electromechanical electricity meter at you house (bad idea!)
The will determine the magnetic force to be exerted

2. Any air gaps that need to be overcome - the distance between the face of the electromagnet and the object you wish to act upon

3. The voltage to power the electromagnets - this has an impact on wire size for the coils to achieve the current and thus the ampere-turns to create the required magnetic forces.
The current also determines what electronic interface is required - whether a L293D (rated 600 mA) or something way bigger is needed.

4. What mechanism will be used to select the desired frequency (between say 2 Hz and 50Hz)

Tentatively the PICAXE program code can be relatively easy to formulate/write once the hardware is known.

Accordingly if you want help from the fundamental level in achieving your legitimate project, you need to advise what the application is with a good level of detail.
You obviously have some application in mind and desire to achieve same to keep asking this on several forums, so please fill in the black-hole in our needed information so that folks here can assist you..
 

Dippy

Moderator
I haven't time to trawl the whole thread, but from Page 1:-

"I will buy two U-shaped electromagnets. (Size at this stage is unimportant. 2 or 3 inches long.)"

"Size current, power, et cetera will become issues if the initial experiment proves successful."

Eclectic supplied an example - no acknowledgement from OP.
Later on Rossko57 posted an ebay equivalent and was awarded the prize.

Therefore "Lifting a steel billet with a mass several tonnes" isn't really on the menu at this stage.

Personally, I don't see why everyone needs nitty-gritty of the final project to get a small prototype alternating electromagnet working.
On the other hand, all the information needed has been supplied to make a basic driver - apparently not understood.
If the OP wants a no-effort COTS then buy the E/magnets things highlighted by Eclectic or Rossko and buy a function generator and amplifier.

If the thread (cerebrally) offends people then ignore it and get on with the decorating.
If I want to wear myself out pulling teeth then I'll go on a dentistry course :)
 
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