i was wondering how to go about getting a small circuit designed, i realise this would need paying for £ which i am willing to do. I am sorry if this is in the wrong section, but i thought as it is a wireless project i thought this would be a good place to go. Ok about me i have worked with basic electronics for a number of years but not Design i know that is a whole new field of expertise. so what i want to do is to use as small as i can get away with an Electromagnet that can hold a 10 pence piece without dropping off . for me to then press a remote control button and the 10 pence piece is released from the electro magnet and drops off. I want to run it all from a 3.7v recharge Battery in as small a pack as i can. so can anyone advise me where to start looking on how to go about this project please. Many Thanks in advance

 

Are 10 pence pieces even attracted to a magnet?

A quick search indicates that some of them are. So step one is taken care of.

How long does it have to hold it? That will have a major impact on how small the battery can be.

An alternative is to use a permanent magnet to hold the coin and then use the wireless electromagnet to counter the permanent magnet so as to release the coin. That will require very little battery (just enough to power the receiver plus a tiny bit more for a pulse to the electromagnet long enough to ensure the coin release).

 

I don't know much about UK Coinage,
but I would be willing to bet that none of your Coinage contains Ferrous-Metals,
meaning that they will not stick to a Magnet.

You could probably design a mechanical steel lever system of some sort that would work,
but that would increase the bulk or size of the project.
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I don't know much about UK Coinage,
but I would be willing to bet that none of your Coinage contains Ferrous-Metals,
meaning that they will not stick to a Magnet.

You could probably design a mechanical steel lever system of some sort that would work,
but that would increase the bulk or size of the project.
.
.
.

Thank you for your reply, we do have several coins that can be used with magnets and some of which I use on other projects, 1 pence piece, 5 pence and 10 pence pieces uk coins.

 

Are 10 pence pieces even attracted to a magnet?

A quick search indicates that some of them are. So step one is taken care of.

How long does it have to hold it? That will have a major impact on how small the battery can be.

An alternative is to use a permanent magnet to hold the coin and then use the wireless electromagnet to counter the permanent magnet so as to release the coin. That will require very little battery (just enough to power the receiver plus a tiny bit more for a pulse to the electromagnet long enough to ensure the coin release).

Thank you so much for taking the time to look into this, as you may have guessed from my profile name I am a Magician here in uk and my thoughts led me to an idea I would love to try.. take a can of coca cola or any soda can and remove the whole lid of the can, which is very easy and kept in perfect condition after removal. I want to fit the electromagnet etc to the inside of the lid holding the 10 pence coin probably for about 15 minutes and the whole lid placed back on the empty can, then with the press of a remote button the electro Magnet releases the coin, but having said that I am expecting there would need to be some type of circuit connected to the electromagnet to make this happen.

 

If everything is inside an enclosed metal can (particularly if the pop can is "unopened"), then you may have problems getting enough of an RF signal into the can for it to successfully recognize the signal to release the coin.

 

Steel was added to the penny from and after ~1996 and to the 10 pence from 2012.

Soda cans are made of aluminium and hence are not magnetic.

 

Soda cans are made of aluminium and hence are not magnetic.

So?

 

Are 10 pence pieces even attracted to a magnet?

Some are, some aren't. They used to be cupronickel and it was changed to plated steel in 2012. Both types are in circulation.

 

I concur with @WBahn, The best scheme is to use a permanent magnet for holding, then release the coin using either a cancelling field from an electromagnet, an actuator, or both.

It is my surmise that the hybrid option is probably the most viable since the current required to overcome the permanent magnet is likely to be high, and a small actuator might be hard pressed to remove the coin alone, and still use a permanent magnet that doesn’t risk dropping the coin from a small external mechanical shock.

On possibility is this tiny linear actuator intended for use in cameras. They only cost around $2USD (+ shipping) each, and are powered by a tiny standard stopper motor. I really like these things and have several so if an application strikes me, I will have them on hand.

​

Alternatively, it might be possible to charge a small supercap to produce a pulse for more defintiive overpowering of the permanent magnet. In any case I would treat the magnet as consumable since each activation will reduce its magnetic field to some extent. A small NdFeB (Neodymium-Iron-Boron) disc rare earth magnet seems to be a good option, and—though my concerns about the weakening field may prove irrelevant—making it easily replaceable seems prudent.

As was pointed out using radio remote control could be your biggest challenge—but since it is unlikely the gimmicked can will can otherwise be made freely examinable, either an exchange will be required or some other redirection employed.

Possible solution include:

• creating a “window”, concealed with something radio-transparent, possibly on the bottom of the can;

• making an antenna that feeds from outside to a probe inside the can;

• using IR (infrared) remote control methods which would permit a much smaller aperture, and could in turn be radio controlled;

* (possibly) using ultrasonics, which might work through the can with no aperture—though for a younger audience you need ot be sure the frequency is well above 20kHz to avoid detection.

The bottom line is: in the absence of further information concerning the intended effect and the patter you have in mind, it appears to be doable, at least for some versions of what you might want.

Then again., appearances can be deceiving…

 

So the whole device would be part of a "Magic Trick" illusion, which makes it seem a reasonable goal.
The biggest part of the challenge will be receiving a signal thru an aluminum soft drink can. The other challenge will be making the can feel "right" to the volunteer handling it. And the other challenge will be recharging the battery inside..

 

Hi all firstly thank you all so much for your thoughts on this project, absolutely it is a Magic effect i am trying to get working, so to open a can of cola i actually open the can and poor away the contents, then i use some 150 wet and dry sand paper, in a circular motion for around 3 minutes then the whole lid pops off. Now i am at that stage i fit a strip of aluminium fitted cross ways on the inside of the lid i can then feed that inside of the can and it all stays in place, of course the can ring has been pulled so it does look like and proven to be an empty can. it will be remote key fob that actuates. now this is the interesting part i have a small circuit which delivers 3.7 volts forward motion that has a magnet on a solenoid that holds, and when i press the key fob the circuit delivers a 1.5 volt on the neg pole of the solenoid and this is enough to allow the magnet to release. so in my case the coin is attached to the solenoid 3.7 volts holds it in position, reverse half the voltage and the coin falls off. all of that i have attached to a rechargeable lithium battery, which all as a temp measure with a recharge circuit i have hot glued to the inside of the can lid. except the solenoid because it is far too big, so i have just hot glued that to the inside wall of the can just to prove it. so i know it works but what i wanted to do was to fit sub minature parts with a tiny electro magnet so it all sits nicely onto the lid. and to get it right have a circuit designed that is small enough and will have the forward/reverse voltages required for the electro magnet, with a recharge circuit and remote circuit built in so that it ends up as a single circuit board. does that make sense. i forgot to mention the can is open so the keyfob works fine, and to recharge the battery the whole lid pops off so i can plug in and recharge.

 

An easy way to reduce the power consumption a lot has already been presented, which is to only power the coil to provide a cancellation of a permanent magnet's field.

 

Hi all firstly thank you all so much for your thoughts on this project, absolutely it is a Magic effect i am trying to get working, so to open a can of cola i actually open the can and poor away the contents, then i use some 150 wet and dry sand paper, in a circular motion for around 3 minutes then the whole lid pops off. Now i am at that stage i fit a strip of aluminium fitted cross ways on the inside of the lid i can then feed that inside of the can and it all stays in place, of course the can ring has been pulled so it does look like and proven to be an empty can. it will be remote key fob that actuates. now this is the interesting part i have a small circuit which delivers 3.7 volts forward motion that has a magnet on a solenoid that holds, and when i press the key fob the circuit delivers a 1.5 volt on the neg pole of the solenoid and this is enough to allow the magnet to release. so in my case the coin is attached to the solenoid 3.7 volts holds it in position, reverse half the voltage and the coin falls off. all of that i have attached to a rechargeable lithium battery, which all as a temp measure with a recharge circuit i have hot glued to the inside of the can lid. except the solenoid because it is far too big, so i have just hot glued that to the inside wall of the can just to prove it. so i know it works but what i wanted to do was to fit sub minature parts with a tiny electro magnet so it all sits nicely onto the lid. and to get it right have a circuit designed that is small enough and will have the forward/reverse voltages required for the electro magnet, with a recharge circuit and remote circuit built in so that it ends up as a single circuit board. does that make sense. i forgot to mention the can is open so the keyfob works fine, and to recharge the battery the whole lid pops off so i can plug in and recharge.

Given the additional information, I would investigate using an array of very small rare earth magnets with coaxially arranged solenoids that are arranged to cancel the field of the magnets. This way, holding will be free, and the size can be reduced. I am picturing it something like this:

​

I would expect better results using a scheme that charges a capacitor and delivers a pulse to the solenoids rather than trying to deliver the current needed from the Li cell directly.

Since are starting with an “empty“ can, you have an aperture already which simplifies things for the radio control part, but the higher the frequency (shorter wavelength) the better, so 2.4GHz would probably be more reliable than lower frequency options.

 

Ya’akov
Thank you so much for all your thoughts and Guidance, i will certainly investigate your methods

 

An easy way to reduce the power consumption a lot has already been presented, which is to only power the coil to provide a cancellation of a permanent magnet's field.

Thank you Misterbill2 i think its exactly that which i am looking for to happen, the only sticky point is finding someone who would be able to put all of this into a schematic so i can get boards made.