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Topic: AC current generator (Read 489 times) previous topic - next topic

shimonchick

Hello.
I want to make(or buy) some(5) ac function generators to control 5 electromagnets. They need to be small and portable, So I can attach them to a glove. The project is trying to imitate/upgrade The flexus project.I will need to set them to different frequencies to avoid interference. I will also have to avoid 50hz and its harmonics. I saw that there is a way to do this using an external audio card, but I don't like this solution because it's not portable. I need to have  5 small frequency generators that can make 5 different frequencies. Is there some PCB or microcontroller that can do that? Any links/suggestions are appreciated.

FantomT

For low frequencies (<200 Hz or so) any arduino will do. In theirs work freq. 75-125 Hz, and since 3-rd harmonics of the lowest 75 doesn't interfere with the highest 125, you even don't need a pure sine. Rectangular pulses would be o'k to drive electromagnets.
Perfectionist, like me, would make clean sine wave oscillators, combining arduino UNO + LTC1665 (8 channel DAC) to create a 5-8 channels generator. Than drivers, any audio amplifier 'd be o'k.

shimonchick

#2
Oct 30, 2018, 07:14 pm Last Edit: Oct 30, 2018, 07:15 pm by shimonchick
For low frequencies (<200 Hz or so) any arduino will do. In theirs work freq. 75-125 Hz, and since 3-rd harmonics of the lowest 75 doesn't interfere with the highest 125, you even don't need a pure sine. Rectangular pulses would be o'k to drive electromagnets.
Perfectionist, like me, would make clean sine wave oscillators, combining arduino UNO + LTC1665 (8 channel DAC) to create a 5-8 channels generator. Than drivers, any audio amplifier 'd be o'k.
Thank you for the suggestions. Now I have some idea on the tools needed, but how do I go and do it? I saw that I can use PWM, but then what? Do I use an opamp, do i switch the pinmode between INPUT and OUTPUT, do I use DAC? I have googled a couple of approaches and don't know which to chose. I want to have 5 channels with different frequencies between 50 and 200Hz.

FantomT

Thank you for the suggestions. Now I have some idea on the tools needed, but how do I go and do it? I saw that I can use PWM, but then what? Do I use an opamp, do i switch the pinmode between INPUT and OUTPUT, do I use DAC? I have googled a couple of approaches and don't know which to chose. I want to have 5 channels with different frequencies between 50 and 200Hz.
Arduino can't generate sine wave by itself, so first step you need a DAC.  One channel with De-MUX, or multychannels. If last sentence is too complicated to comprehend, than do your google-work, find something "arduino sine wave generator" that is not shocking you , and try to replicate. Than stepping from 1 channel to 5 should not be an obstacle.

charliesixpack

#4
Oct 31, 2018, 07:59 pm Last Edit: Oct 31, 2018, 08:00 pm by charliesixpack
If you need an analog output you can use an arduino due with this library...
https://github.com/cmasenas/SineWaveDue

If you can get by with a pwm output you can use an uno and use this library...
https://github.com/cmasenas/SineWave

If you need 5 sine waves you need multiple arduinos.

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