Hi all,
I want to use a functional generator to control a electric magnet, the functional generator could generate a sine/cosine signal, and I have a L298N motor driver to drive my 12v-600N electric magnet. What should I do to connect the functional generator with the motor driver in order to let the magnet generate field according to the signal I have?
Because the signal could be positive and negative voltage, I hope the driver could switch the current and make the polarity reversed.
If you have better idea for the control circuit, please let me know. Thanks a lot!

 

May be wrong but don't think your L298 is going to like a sine wave as an input. You may get better help if you explain what you are trying to do.

 

What is the function of the electro magnet?
Some details would REALLY help on ability to offer advice!
Max.

 

May be wrong but don't think your L298 is going to like a sine wave as an input. You may get better help if you explain what you are trying to do.

Hi, I want to use the magnet to generate an alternative field in order to drive the diaphragm.

 

What is the function of the electro magnet?
Some details would REALLY help on ability to offer advice!
Max.

Hi, Max,
What I want is to use the magnet to generate a sine waveform alternative magnetic field to drive our loudspeaker. This loudspeaker is working underwater, so I have to make it by hand. The power will be larger than normal loudspeaker and the reason why I choose motor drive is that it could control the amplitude.

 

Assuming the frequency range is in the audio range (Say 50 hz to 20 Khz) then an normal audio amplifier of suitable power rating would be the simplest solution. (I say suitable power rating as you have given no details of the resistance and inductance of the electro magnet.) Your electro magnet will almost certainly have a much higher inductance than a normal loudspeaker so for the higher frequencies you will need a much higher drive voltage than at low frequencies. Have you taken these factors into consideration ?

Les.

 

Another thing to take into account when considering power requirements is that a diaphragm moving water has a much harder job than one moving air (as in a normal loudspeaker).

 

Hello,

What power would you need?
In this post there are audio power opamps upto 68 Watt mentioned:
https://forum.allaboutcircuits.com/threads/components-selection-guide.65137/#post-448192

Bertus

 

If you want to drive this electro-magnet in the audio range then I suggest a large audio power amplifier. This will work from about 20Hz to 20kHz. Lower frequencies (down to DC) might be possible with modifications.
You don't say what voltage or current will be required. This will set the power rating of the amplifier.
You can build an amplifier but easier and often cheaper to buy something. Look for something second-hand on Ebay for example. You won't need a pre-amplifier so a simple "line in" power amplifier will be OK. A good quality manufactured amplifier will usually include safety circuits that will protect against short circuits and excessive output current (and Safe Operating Area of the output transistors). Important here because your load may be very inductive.
An audio amplifier will deliver the positive and negative signal.

 

Assuming the frequency range is in the audio range (Say 50 hz to 20 Khz) then an normal audio amplifier of suitable power rating would be the simplest solution. (I say suitable power rating as you have given no details of the resistance and inductance of the electro magnet.) Your electro magnet will almost certainly have a much higher inductance than a normal loudspeaker so for the higher frequencies you will need a much higher drive voltage than at low frequencies. Have you taken these factors into consideration ?

Les.

Hello, Les,
We are building a extra-low frequency source, from 1Hz-50Hz, is it possible for audio amplifier?

 

If you want to drive this electro-magnet in the audio range then I suggest a large audio power amplifier. This will work from about 20Hz to 20kHz. Lower frequencies (down to DC) might be possible with modifications.
You don't say what voltage or current will be required. This will set the power rating of the amplifier.
You can build an amplifier but easier and often cheaper to buy something. Look for something second-hand on Ebay for example. You won't need a pre-amplifier so a simple "line in" power amplifier will be OK. A good quality manufactured amplifier will usually include safety circuits that will protect against short circuits and excessive output current (and Safe Operating Area of the output transistors). Important here because your load may be very inductive.
An audio amplifier will deliver the positive and negative signal.

Hello, Marley!
Yes, we are trying to build an amplifier to generate large power signal. The working voltage is 9v-12v, current is 2A-3A, so we need a very large power amplifier. I purchased LM675 and OPA548, but when the load decreased from 20KOhm to few KOhm, output gain decreased very quickly, what's the reason of that?

 

Hello,

What power would you need?
In this post there are audio power opamps upto 68 Watt mentioned:
https://forum.allaboutcircuits.com/threads/components-selection-guide.65137/#post-448192

Bertus

Hello Betus,
Thanks for your list!! I purchased LM675 as amplifier, this lists really helps a lot!!