Audio Signal Controlling Electromagnet

Discussion in 'The Projects Forum' started by jamd, Jan 27, 2014.

1. jamd Thread Starter New Member

Jan 27, 2014
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Hi,
I'm a total newbie, so I have a project where I want to manipulate some ferrofluid with an electromagnet using an audio input (from say an iPhone). My initial thoughts was to have say 3 band passes corresponding to 3 electromagnets so you can see the individual elements of the song (such as bass ext).

I was hoping you guys could point me in the right direction in what to read up on how I can get this project rolling.

Like I said total newbie, had some experience with circuits from A level physics but thats about it!!

Many Thanks!
James

2. shteii01 AAC Fanatic!

Feb 19, 2010
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You are probably better off with three different filters.

Generally speaking, audio is from 2 Hz to 20 kHz. You have to break it down into three ranges. Use low pass filter for low frequencies. Use bandpass filter to pass middle frequencies. Use high pass filter to pass high frequencies.

So. Find out the voltage of the iPhone output. Find out voltage input of electromagnet. Then you can design the filters.

jamd likes this.
3. djsfantasi AAC Fanatic!

Apr 11, 2010
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Speakers are really electromagnets.

Driving multiple speakers by frequency is done through a circuit called a speaker cross over.

Another approach is to research color organs. Basically your original idea.

Is this enough information to research? Also, I'd ask myself what field strength you need to drive your ferrofluid.

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4. jamd Thread Starter New Member

Jan 27, 2014
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So if I were to do this speaker cross over circuit and then connect the input to an AUX jack and outputs across the electromagnets this would get the desired effect? Id need to create something to amplify the power of the signal as the electromagnet wouldn't generate a magnetic field strong enough to have the desired effect.

Sorry about the questions like I said total newbie!

5. #12 Expert

Nov 30, 2010
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Unless there is something you aren't telling us, I think this is a lame idea. Consider the refresh rate of a TV. Anything faster than 30 frames per second looks like a continuous movement to a human. What do you expect to see at 300 or 3000 cycles per second?

I think the ferrofluid will just seize up and you will see basically nothing.

Keep talking. Maybe we can work this out.

6. GopherT AAC Fanatic!

Nov 23, 2012
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Ferro fluid is going to need more power than a headphone jack from your iPhone. You need some type of amplifier.

Do you know what magnetic field strength your ferrofluid will need for a reasonable response?

7. jamd Thread Starter New Member

Jan 27, 2014
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I had this exact discussion with my physics teacher this morning actually, is there a way of "scaling down" a frequency of a wave. For example when we get a 3000 hz wave we scale it down by a factor of 1000 (as an example of course so we get 3hz) and use that for the input of the electromagnet. How would these (https://www.youtube.com/watch?v=bozAVSIHvh4) get around the high frequency problem? I mean the way these work is by a motor spinning some sort of fan pushing water up to a certain heigh. Now the height depends on the power of the motor so can't I just do exactly what there doing but instead vary the power across the electromagnet.

Many Thanks!!

8. jamd Thread Starter New Member

Jan 27, 2014
5
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A headphone jack of an iPhone I think only throws out 300 millivolts (and not going to be a great deal of current so no where near enough power), so I was thinking of having the circuit amplified by a mains supply. I have no idea how I would even create such a circuit let alone incorporate a mains supple to amplify it. Or weather thats possible aha

Many Thanks!!

9. jamd Thread Starter New Member

Jan 27, 2014
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I was thinking of using a circuit like this as a basis (http://www.jameco.com/Jameco/workshop/diy/ledcolororgan.html) and instead of having the LED output replace these with electromagnets, but how would a) amplify the signal b) Vary the voltage across the electromagnets with the amplitude/loudness of the individual bands

10. GopherT AAC Fanatic!

Nov 23, 2012
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You can use frequency dividers like the CD4040 chip that can divide by 2 many times (each outpot has different divide by 2 factor for one input frequency).

For a quick test, you could pull a signal generator out of your physics teacher's closet (or make a 555 timer square wave generator of your own, then output that to a standard stereo receiver (\$20 on craigslist.com -or- use your brother's stereo). You might also track down a signal generator app for your iPhone as the frequency source.

Using a signal generator will give you an idea of how the ferrofluid will respond to frequency before you build a crossover and frequency divider. The fluid may not respond as you expect and it will save you a bunch of time.

11. #12 Expert

Nov 30, 2010
16,346
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Here is a concept drawing of an amplifier from 40 Hz to 160 Hz. That's all of a bass guitar up to the 8th fret. The first stage gives an adjustable gain of 1 to 11 and the second stage gives a gain of 20, and it can push some reasonable current.

No promise that this is how it will end, but it's a start.

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