11-03-2021, 03:11 PM
(11-03-2021, 11:26 AM)solid Wrote:(11-03-2021, 09:40 AM)Erik Josefsson Wrote: Meanwhile, can I ask about the HiFi headphone amplifier you used? This is a bit beyond where my learning curve ended when I studied (basic) circuits, but I wonder 1) if that amplifier would be powerful enough to pull a 35 gram neodym magnet (see picture) hanging in a spring into a forced oscillation? and 2) Do you think you could force a spring to oscillate with frequencies as a low as 1-2 Hz if you used phyphox's MULTI TONE GENERATOR (e.g. 440 and 441 Hz)? Obviously you would have to connect an iron core electromagnetic coil of reasonable size to the headphone amplifier instead of headphones. And be careful with distance etc.
Dear Erik,
I add a pdf file with all what I know about the amplifier. It is very useful when the generator has a high internal resistivity. But I do not think that it will work at 1-2 Hz, it is a sound amplifier.
You could use multi tone generator if you would add diodes and will keep only the envelope of the signal (4 diode bridge). Your resonance project is very useful and it would be great if it will work so using only smartphone with some minor addition. But I have not tried yet the forced oscillations of the spring with a mass. A headphone amplifier should be useful also to preamplify the smartphone signal before passing it to the diodes...
Best
Mikhail
Thank you very much for the pdf Mikhail. That's exactly what I needed.
With regards to the diode bridge, I have to apologize for my ignorance, but is it really needed? My first simple thought was that since I clearly can hear the volume of the sound oscillating when I listen to 440 Hz and 441 Hz at the same time (generated by the MULTI TONE GENERATOR), then that oscillating volume simply represents a periodic variation of the energy in the magnetic coil of the phone's speaker. So, I would basically only have to make the energy in some other magnetic coil vary since it is only the variation (envelope?) I want. I don't want the sound of the variation.
Imagine you'd generate 25.000 and 25.002,23 Hz, you would still get a 2,23 Hz "energy beat" but you would not hear anything (at least I would not). And, in this case, you would not want to either.
So what I asked was if that 2,23 Hz "energy beat" (which is clearly there) could somehow drive change in a magnetic field of a standard education coil with a laminated iron core.
I made a ridiculously simple sketch with standard school equipment, see attachment. But again, I am sorry to say that I'd have to read up to figure out why I actually need a 4 diode bridge to make it work, and not only enough juice from the amp.
Best regards.
//Erik