Idea about ELF design (extreme low frequency)

Thread Starter

ElectroWarrior

Joined Aug 26, 2018
9
I wanted to design circuit that outputs extreme low frequency, between 4hz and 10Khz. I want to use microprocessor. I have found some microprocessors that outputs that kind of frequency. The problem is the amplitude of the signal. Has to be around 10-12V. Usually the microprocessor outputs 5V. Any idea how can I go with this design and what microprocessor to use.
Thanks
 

ArakelTheDragon

Joined Nov 18, 2016
1,350
I wanted to design circuit that outputs extreme low frequency, between 4hz and 10Khz. I want to use microprocessor. I have found some microprocessors that outputs that kind of frequency. The problem is the amplitude of the signal. Has to be around 10-12V. Usually the microprocessor outputs 5V. Any idea how can I go with this design and what microprocessor to use.
Thanks
Which year are you in the University?

4Hz is not extremely low. Stop playing with these devices about irritating humans and chasing them from your property or similar reasons!
 

Janis59

Joined Aug 21, 2017
1,270
Isnt it easier to produce the ordinary sound vawes via any audio amplifier in the pure-analog way???? If computer is sth "must to be because must to be" then take a "Zeitnitz Sound card" freeware, install in laptop and push audio jack into amplifier. Thera re Your extremely low 0,004 to 40 000 Hz as much any may want, two channels, right and left separately adjustable.
However, if Your neighbours are bit nervous personalities, be warned, US is the land where guns are allowed to be kept at home. Use a proper life jacket!
 

ericgibbs

Joined Jan 29, 2010
11,936
hi EW,
Welcome to AAC.
Is it a square wave signal you need or a sine wave.
If its a sqrwave, you could use a transistor to raise the level from 5V to 12V.
What sort of power levels are you looking for.?
E
 

Thread Starter

ElectroWarrior

Joined Aug 26, 2018
9
Thanks for the welcome. Yes I will use square wave with positive offset. The output should be 10V (0 to 10V) no negative voltage. But If I use transistor like npn I will have flicker noise added to it right??
hi EW,
Welcome to AAC.
Is it a square wave signal you need or a sine wave.
If its a sqrwave, you could use a transistor to raise the level from 5V to 12V.
What sort of power levels are you looking for.?
E
 

Thread Starter

ElectroWarrior

Joined Aug 26, 2018
9
I use AVR controllers for this, and it is difficult to imagine a controller that can't do the job.

I am currently running Jesper Hanson's Mini DSS algorithm in a project. 1 Hz to 65kHz in 1 Hz steps no problem.

http://www.radanpro.com/Radan2400/mikrokontroleri/Jesper's AVR pages - MiniDDS.htm

There are several pages on the web that reference this design so you will find it well explained.
It looks good. Just two question whats you output voltage on the square wave? It looks like the output voltage is not that stable at Vomax (like has small oscillations) ? But I guess that can be improved. Is really simple schematic though. Really easy to do it.
 

DickCappels

Joined Aug 21, 2008
6,979
Using an 8 bit DAC (or R-2R network like Jasper used) you should be able to get 255/256 of the power supply voltage which will probably be between 3 and 5 volts, your choice. A simple grounded emitter NPN with a collector resistor going to 10 or 12 volts will amplify the signal to ...10 or 12 volts. Drive current will be limited by the resistor size. It can be improved by adding a a buffer stage or a totem polie output like that shown on the right side of the inverter circuit below.

upload_2018-8-27_18-36-39.png

"Flicker noise" as I understand it is 1/f noise and a small signal phenomenon. Is that what you are thinking about? Being a digital output flicker noise should not be an issue in any but extremely exotic applications.

If you use a 20 MHz crystal for your clock with Jesper's DDS circuit and his DDS loop you should see about 1 us of jitter. Compare that with 100 us per cycle at 10 kHz.

If you need it cleaner you could use a filter or if you are only in need of square waves you can also make them by inserting output instructions inside timing loops. A 20 MHz clock gets you 50 ns resolution.
 

Thread Starter

ElectroWarrior

Joined Aug 26, 2018
9
hi EW,
Not sure what you mean by 'flicker noise' on the output.?
E
Flicker noise is the noise generated from the npn and pnp transistors at very low frequencies. Usually up to 10KHz and is exponential. The formula is like Fn=Fo* EXP(1/f) something like that. Is also called 1/f noise. CMOS doesnt have that much flicker. But in general it will mess up the design if you dont account the flicker noise.
 

Thread Starter

ElectroWarrior

Joined Aug 26, 2018
9
Using an 8 bit DAC (or R-2R network like Jasper used) you should be able to get 255/256 of the power supply voltage which will probably be between 3 and 5 volts, your choice. A simple grounded emitter NPN with a collector resistor going to 10 or 12 volts will amplify the signal to ...10 or 12 volts. Drive current will be limited by the resistor size. It can be improved by adding a a buffer stage or a totem polie output like that shown on the right side of the inverter circuit below.

View attachment 158763

"Flicker noise" as I understand it is 1/f noise and a small signal phenomenon. Is that what you are thinking about? Being a digital output flicker noise should not be an issue in any but extremely exotic applications.

If you use a 20 MHz crystal for your clock with Jesper's DDS circuit and his DDS loop you should see about 1 us of jitter. Compare that with 100 us per cycle at 10 kHz.

If you need it cleaner you could use a filter or if you are only in need of square waves you can also make them by inserting output instructions inside timing loops. A 20 MHz clock gets you 50 ns resolution.
I have more experience as device engineer. Have not done practical circuit design. This looks like cascade amplifier to me. I'll give it a try. Maybe you are right maybe 1/f doesnt matter in digital design that much. Yes you are right about flicker noise. Is 1/f noise.
 

ericgibbs

Joined Jan 29, 2010
11,936
hi EW,
You could a MOSFET amp say a 2N7000 or 2N7002 if you prefer a CMOS to TTL device.

Can you say what the final application is for the project.?

E
Like this example, providing the signal inversion does not cause you a problem.
 

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Thread Starter

ElectroWarrior

Joined Aug 26, 2018
9
ELF. Is this for transmission / radio ?
No this is for contact mode. Is really hard to do a transmission on the ELF the problem is the size of the transmitter. I heard there is a new technology now but I can not find anything on internet. As from my knowledge there is two ways to transmit ELF. As phase modulation like this Vn=Vo*sin(wt + ELF). Where w is usually 80K for the ELF up to 1K or so (maybe 1K is to high. w= 2*pi*frequency). This is just assumptions. The second is to modulate the electro magnetic pulse (which I dont know how to do it).
Anybody with more info on this would be extremely helpful.
 

Thread Starter

ElectroWarrior

Joined Aug 26, 2018
9
hi EW,
You could a MOSFET amp say a 2N7000 or 2N7002 if you prefer a CMOS to TTL device.

Can you say what the final application is for the project.?

E
Like this example, providing the signal inversion does not cause you a problem.
It is for personal maybe later business application. I dont want to give details. But is for a health applications.
 

Picbuster

Joined Dec 2, 2013
1,026
I wanted to design circuit that outputs extreme low frequency, between 4hz and 10Khz. I want to use microprocessor. I have found some microprocessors that outputs that kind of frequency. The problem is the amplitude of the signal. Has to be around 10-12V. Usually the microprocessor outputs 5V. Any idea how can I go with this design and what microprocessor to use.
Thanks
Use PIC24FJ128GC010 with internal 10 bit DAC followed by an opamp and mosfet to produce power.

Picbuster
 
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