I have the electromagnetic fear...

[poutpout]

Thanks arhi!

I have just made another test and it works a litlle bit more. I used safety pins instead of small nails because I have just a 9 volt battery right now. I think the current is not strong enough. I feel that, if I have bigger voltage, things will move a bit like the clip. But it looks like changing polarity is doing something though...

But, if he just do on/off, what is tha big circuit there?
ImageShack - Hosting :: par02gf1.jpg

 

[poutpout]

So, you are still on the right track for that display.

OH! YEAH! COOL! That's means, I'll will have to have a look on that H Bridge that you suggest me, right?

 

[KMoffett]

But, if he just do on/off, what is tha big circuit there?ImageShack - Hosting :: par02gf1.jpg

Though not definitive from the photo it's probably interface circuitry (to a computer?) and power transistors with heat sinks to drive the electromagnets' coils with high current.

Ken

 

[poutpout]

it's probably interface circuitry (to a computer?) and power transistors with heat sinks to drive the electromagnets' coils with high current.

... can you feel the question coming...

 

[arhi]

... can you feel the question coming...

you can use parallel port of the computer to drive 8 transistors that will energise magnets. Note that when driving magnet's using transistor you have to have the protection diode (or the transistor will fry as you were warned in the store). Search the forum and you will find many examples on how to use par port to drive external eq from windoze .. you can either drive transistors directly, or even better, in order to protect your pc from possible spikes, use optocouplers between your board and pc

some useful links:
Parallel port output
https://www.electro-tech-online.com/threads/relay-uln2803-circuit.21656/

hope this helps

 

[ericgibbs]

Sorry, I don't know. I don't have multimeter but I have the Data Sheet maybe it will help?
**broken link removed**

Looked at the datasheet, which model number do you have.?
They range from about 3W thru 17W.

 

[poutpout]

Looked at the datasheet, which model number do you have.?

Magnetschultz GMHX 030 X00 D02
30mm Dia 24mm Long 24VDC 156 mA 280N Weight 100g
**broken link removed**

you can use parallel port of the computer to drive 8 transistors that will energise magnets.

Unfortunately, you pointed me to great information but I am on MAC.

I have found that, it it use with Arduino.
**broken link removed**
The problem is, I need to control for now, at least at least 9 (or it can be 6). Also, in that schematic, there is no diode protection, is it ok?

I don't absolutely need to control them by computer (for now). I'd like to use the easiest solution.

Thanks again!
Julie

 

[arhi]

Unfortunately, you pointed me to great information but I am on MAC.

I have found that, it it use with Arduino.
**broken link removed**
The problem is, I need to control for now, at least at least 9 (or it can be 6). Also, in that schematic, there is no diode protection, is it ok?

I don't absolutely need to control them by computer (for now). I'd like to use the easiest solution.

I do not use my mac for this stuff so not sure what is possible (for sure I know my macbookpro have no parallel port) but what I can see from here is something like this:

1. if you want automation
- you need uC to control the magnet driver
- you can either use uC with USB support and talk to your mac or forget about control from computer all together and preprogram behaviour in uC / add some input buttons to "store/replay" patterns, program some "beats" that you can change by pressing a button on the uC

2. you do not want automation
- connect those xyz magnets via xyz switches and "play" the tune on the switches (not too interesting imho)

You can use arduino as your "uC platform" or you can build one yourself, check out some nice tutorials on "microcontrolers" faq. Again, not sure how all that work with mac, I dedicated one windoze box for electronic work as all my linux and osX boxes cannot help with the basic tasks when electronic work is at hand The virtualBox helps as it can "pass trough" the USB port so you can get some things done, but again, you need to run windoze in the virtualbox space ...

As for the driver used on the schematic, L293D has built in diodes, donno about L293E that they use in the example, but you should need them if you want to protect the equipment (and also if you want to properly switch polarity). Check the datasheet for L293, you will find nice examples there.

 

[poutpout]

You can use arduino as your "uC platform" or you can build one yourself,

I think I don't want to go there...

About the L293E a friend wrote me: "If you are reversing the polarity via the H Bridge I suspect it is stating that you do not use a back EMF diode. As it would stop current flowing when you reverse polarity. And as such if the H Bridge IC is designed for driving inductive loads (E.g. motor or electromagnetic) it should be able to handle the back EMF.

Is he right? Should I use the L293D instead?

If I don't control the electromagnets by computer, how do I drive the H Bridge? With a 555?

 

[ericgibbs]

I think I don't want to go there...

About the L293E a friend wrote me: "If you are reversing the polarity via the H Bridge I suspect it is stating that you do not use a back EMF diode. As it would stop current flowing when you reverse polarity. And as such if the H Bridge IC is designed for driving inductive loads (E.g. motor or electromagnetic) it should be able to handle the back EMF.

Is he right? Should I use the L293D instead?

If I don't control the electromagnets by computer, how do I drive the H Bridge? With a 555?

hi,
You can add external diodes to a basic LM293, look at this image.

 

[audioguru]

The 4 diodes clamp the voltage spike from the inductor to 1 diode forward voltage drop (about 0.7V) above the positive supply and below ground (negative).

 

[MrAl]

Hi,


Just to note, suppressing the inductive kickback from a coil is always a good
idea. Not only does it protect the user from a dangerous shock, it also
protects the wire insulation. When a coil is disconnected from a circuit where
there is current flowing, a high voltage is generated by the magnetic field.
This high voltage seeks a path for current to flow and sometimes may find
it through the wires insulation which may be only rated for 400v or so.
Repeated discharges through the wire insulation could start to break it
down over time, eventually causing a permanent short and thus rendering
the inductor useless.

Also to note, it's not necessary for the user to touch the bare wire
to get a shock. Depending on the voltage generated it could punch
through the insulation and still shock the user.

 

[poutpout]

Also to note, it's not necessary for the user to touch the bare wire
to get a shock. Depending on the voltage generated it could punch
through the insulation and still shock the user.

Thank you! I help my electromagnetic fear...!

 

[MrAl]

Hi again,

Oh you are welcome. I've even gotten shocked from relay coils in the past
so whenever i get a new relay the first thing i do is solder on a catch diode
before i ever energize it.
Other things that can kickback are transformers, and really anything with a
coil of wire in it.

 

[poutpout]

According to this: **broken link removed**
somebody wrote: "If you are reversing the polarity via the H Bridge I suspect it is stating that you do not use a back EMF diode. As it would stop current flowing when you reverse polarity. And as such if the H Bridge IC is designed for driving inductive loads (E.g. motor or electromagnetic) it should be able to handle the back EMF.

3 questions:
1- Is he right?
2- Can I use the L293D instead in the same circuit?
3- If I don't control the electromagnets by computer, how do I drive the H Bridge? With a 555?

 

[ericgibbs]

According to this: **broken link removed**
somebody wrote: "If you are reversing the polarity via the H Bridge I suspect it is stating that you do not use a back EMF diode. As it would stop current flowing when you reverse polarity. And as such if the H Bridge IC is designed for driving inductive loads (E.g. motor or electromagnetic) it should be able to handle the back EMF.

3 questions:
1- Is he right?
2- Can I use the L293D instead in the same circuit?
3- If I don't control the electromagnets by computer, how do I drive the H Bridge? With a 555?

hi,
Unless I am missing something I cannot see in that article that he is saying dont fit diodes.?

I would fit diodes on the basic LM293 or buy a LM293D.
Look at the data we have posted, it shows clearly diodes are fitted for inductive loads.

If you dont use a PC to drive the H-Bridge yu will have to use logic ic's.

 

[poutpout]

Thank you ericgibbs and thank you all! I think I'm in that state that I should try one and see.
Thanks a lot! I really appreciated your help!
... see you!

 

[poutpout]

Better still use an opto coupler circuit.

It took me some times but now I think I understand why you suggested me tu use an opto coupler. Yes, it can be a good solution.

By any chances, do you know some schematics with opto coupler who can drive electromagnets?

 

[poutpout]

Because I am a girl, because I am young and because I want to know, I asked the guy who did the video I posted at the beginning of the thread YouTube - particle by Kanta Horio how this thing works and if he really did reverse polarity, etc.

This is what he said: Yes, I changed the polarity and also just turn them on and off. And I used just relays for changing polarity, and transistors for turn them on/off. I use a self made MIDI-digital out converter with AVR microcontroller (AT90S8515). I made this one around 5 years ago so I may use Arduino if I start this project now.

I don't get how a relay can switch the polarity of the electromagnet? Relays are not just for on/off?

 

[audioguru]

I don't get how a relay can switch the polarity of the electromagnet? Relays are not just for on/off?

A double-pole double-throw relay or switch can reverse the the terminals of a motor, electromagnet or battery.