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### Topic: How to regulate a magnetic field? (Read 3141 times)previous topic - next topic

#### itdepends

##### May 23, 2012, 06:47 pm
to realize my semester project I need some help for the technical execution. I have the intention to regulate a magnetic field with a musical signal. The electromagnet (Intertec ITS-MS 5030) works with 12Vdc and 600mA. Voltage and current should be modulated by musical signals. The modulation of voltage and current should be executed by MAX/MSP and an Arduino board. But the maximum voltage of the Arduino board is 5V so I need to amplify the voltage.
To do this I builded up a non-inverting amplifier. With this I can reach the 12V. In the next step I would need to amplify the current to 600mA. I had the idea to use an transistor for it. My electric engineering skills are very basic so I have no clue how big are the dimension of the  components. Maybe its just the wrong circuit for my target?  For your help I would be very thankful. Any help would be appreciated.

#### terryking228

#1
##### May 23, 2012, 07:03 pm
Hi,

Can you tell us more about what the signal to the electromagnet should be??

-  Music is usually considered to have an Alternating current waveform. If you were to look at the waveform going to a typical loudspeaker, it would be "AC" and the voltage would vary both plus and minus about zero.

- If the "music" is at a quiet or zero point, what do you want the electromagnet to have as a signal?

There seem to be two possibilities:
1. The Electromagnet needs bipolar (AC) waveforms applied, and you need to provide an amplifier capable of both + and - voltage outputs.
2. The electromagnet could have a constant 1/2 of maximum voltage applied (6V) when the music signal is Zero, and then change in the range of 0 to 12V.

What will the electromagnet "DO"??  How will you test if it the system is working correctly?

Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

#### itdepends

#2
##### May 23, 2012, 07:19 pm
Hi Terryking,
My plan is it to analyze the music with MAX/MSP. With the data I get there I would like to modulate the output of the Arduino board between 0 and +5V. So I work only with DC. With the magnetic field I want to control ferrofluid ([/url]http://en.wikipedia.org/wiki/Ferrofluid[/url]) with the intention to visualize the music. I hope its clearer now.

#### terryking228

#3
##### May 23, 2012, 08:00 pmLast Edit: May 23, 2012, 08:02 pm by terryking228 Reason: 1
Hi It,

Do you have the magnet and Ferrofluid yet?  Do you know what the effect on the ferrofluid will be for different currents through the electromagnet?

Maybe some experimentation now to characterize the magnet and ferrofluid will inform what you want to do with the output signal.

PS: This is totally usual Engineering going on here. In the beginning you keep developing more and more questions.  Then the questions become more focused and specific.  Eventually you come up with answers
Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

#### itdepends

#4
##### May 23, 2012, 08:21 pm
I already have both of it. But my tests weren't so successful until now. I tried a car charger but the current fall in. maybe because of the internal resistance of the magnet?

#### Grumpy_Mike

#5
##### May 23, 2012, 10:38 pm
Quote
but the current fall in

What does that mean?

Quote
But my tests weren't so successful until now

Until you do have a successful test you can't proceed. Measure the resistance of the magnet coil with a multimeter to calculate the current you will need to supply. If a car charger fails it looks like you initial estimate of only 600mA is way out.

#### winner10920

#6
##### May 24, 2012, 04:39 pm
I think you need a bigger stronger electromagnet, (or multiple, think pyhsical graphical equalizer!)
try the ferro fluid even with a neodynium magnet, it takes alot of strength to do much just at a close range

#### kf2qd

#7
##### May 24, 2012, 06:26 pm
You are starting out with 2 problems - you want to control current and you want to control voltage. You can do 1 or the other but not both, as they are inter-related.

#### SatCure

#8
##### May 25, 2012, 07:48 am

to realize my semester project I need some help for the technical execution. I have the intention to regulate a magnetic field with a musical signal. The electromagnet (Intertec ITS-MS 5030) works with 12Vdc and 600mA. Voltage and current should be modulated by musical signals. The modulation of voltage and current should be executed by MAX/MSP and an Arduino board. But the maximum voltage of the Arduino board is 5V so I need to amplify the voltage.

No, you've got entirely the wrong idea. You need to provide an external Power Supply Unit (PSU) whose current rating is at least 600mA. You need to use the Arduino to control the voltage output of the PSU.

#### terryking228

#9
##### May 25, 2012, 08:39 am
I would suggest testing this by driving the electromagnet with a typical Hi-Fi audio amplifier and some music.

It seems the electromagnet is rated at about 12 * .6 = 7.2 watts and so most small amplifiers would be OK.

This would probably have frequencies too fast for the ferrofluid to handle, but you could get some idea.  If you have access to an audio generator you could drive the amplifier from that, or drive it from Arduino using the Tone function.

I think that to get "cool looking" response from the ferrofluid you will need to feed data into Arduino and have it process the data in some way to create appropriate signals to send to the amplifier/electromagnet.
Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

#### itdepends

#10
##### May 25, 2012, 01:44 pm
Hey ho,

Thanks for the requests.
@ Grumpy_Mike: The Resistance of the coil is 18?.
rated output: 8,0 Watt
Votage: 12 V DC
8/12=0,6666 =>  600mA
right?
@ winner: the holding power of my magnets is 400N. This is something about 40kg. I think this should be enough, or? The idea with the graphic equalizer is interesting. I already got 3 magnets. We'll see whats technically possible.
@ SatCure: what PSU are you thinking about?
@kf2qd: so would it be enough to regulate the current?
@ terryking: I tested the magnet witch an audio-amp with good success. I used a Ampeg B53 Transistor-Bass-Top. (300Watt@4?, 400Watt@2?) Heres a short video of the test (https://rapidshare.com/files/4162036658/Ferrotest.MOV). What do you think about bridging the output capacitor to get DC output? In this case I could only work witch Audiofiles as an input information. So I couldn't regulate the magnetic field in the way I was thinking about it. But maybe its a good solution.

#### winner10920

#11
##### May 25, 2012, 02:03 pm
That's holding force probably at point blank, you don't really want it to only affect the immediate area, but a larger area so you can see the affect
The magnetic field decays exponentially I believe, so to get a larger reach you need quite a larger magnetic, or push your magnets a little further and use say 15 or 20v,
I've done that before and the only drawback is that after a few minutes you need to allow for cooldown time

#### Grumpy_Mike

#12
##### May 25, 2012, 02:18 pm
Quote
The magnetic field decays exponentially I believe,

No - inverse cube law or inverse square law,
Magnetic field drops off as the cube of the distance from the source (for a dipole).
see:-