I need to feed a signal in the low Hz eg 4Hz into a high impedance coil. Could I do it using a 16kHz signal modulated at 4Hz?
-- Dirk
On a sunny day (Wed, 19 Aug 2009 15:41:47 +0100) it happened Dirk Bruere at NeoPax wrote in :
You need to be more specific. Sure, if you want to control the average current in that coil you could use 16 kHz PWM for example. But not AM, or FM, or whatever.... Polarity change + /- ? How many amps?
If uni-polarity put coil in collector of BJT? Need more data. beep
Basically I need a 4Hz current through the coil, sine wave. The carrier would also be sine wave.
-- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
On a sunny day (Wed, 19 Aug 2009 17:36:41 +0100) it happened Dirk Bruere at NeoPax wrote in :
If you could split that carrier in 2 sine waves, and phase shift one. Modulate that phase shift by the 4 Hz, One carrier on each side of the coil.
If at low voltage level some LC (delay) network where C is a varicap? Then amplify before feeding to coil ends... There may be many ways to do this. I'd go digital...
On a sunny day (Wed, 19 Aug 2009 17:36:41 +0100) it happened Dirk Bruere at NeoPax wrote in :
OR AM modulate and use a diode detector.
That may well be more viable
-- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
Would it work? The output is from a high power audio amp.
-- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
On a sunny day (Wed, 19 Aug 2009 19:03:54 +0100) it happened Dirk Bruere at NeoPax wrote in :
Of course it works :-)
You can use a bridge rectifier on the audio amp output :-)
When ordering this part, specify LM567C
Ooh, class A. That's almost as efficient as the class A class D power amplifier I made: sure, it's only 25% efficient, but it's the most efficient
25% you've ever seen!I wonder how many PICs you'd have to connect in parallel to do this, Jan?
Tim
-- Deep Friar: a very philosophical monk. Website:
On a sunny day (Wed, 19 Aug 2009 13:44:59 -0500) it happened "Tim Williams" wrote in :
That is funny, I did read that other thread about HC04 inverters as audio amps or something... Sure you can use a PIC, and perhaps even its PWM generator, to make a class D audio amp. With 20 mA sink and source and full bridge ..... Or just use the build in comparators to make a Philips - patent type class D. But not enough power for me :-)
I'd just use transformers, balanced AB out from 5V to any impedance speaker. It seems the desire to omit transformers has to do with the desire for full integration. Making things cheaper so to speak... But if you then need transformers anyways for a supply step-up... or exotic 1 Ohm speakers... The impedance matching transformers can give, in transistor amps, also between stages, make it possible to have very high gain with few transistors. My view on 5V audio :-)
People seem scared of inductors.... but why? They are relatively simple and very robust.
or something...
integration.
very robust.
Big chunky things bordering on the mechanical :-)
-- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
Not modulate - just sum, like they did with tape recorder heads. They called the (in your case) 16KHz signal a "bias"; with audio recorders it was well above 20 KHz.
In this case, I'd be tempted to call it "dither", or maybe just "bias" would be good enough.
Have Fun! Rich
On a sunny day (Wed, 19 Aug 2009 21:22:59 GMT) it happened Rich Grise wrote in :
That is so, about bias, but if summing you may as well leave out the 16 kHz, and use the 4 Hz only no? LOL
The reason is I want to use a commercial audio amp to feed a coil with frequencies down to 0.5Hz. Since neither amps nor computer audio cards go down that low I need a trick. Amplitude modulating a 16kHz signal is easy.
-- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
ams"
er
icient
an?
io amps or something...
lass D
ass D.
aker.
full integration.
stors.
and very robust.
As opposed to ferrite beads. Which scarcely exist for frequencies below a MHz - though I've occasionally been embarassed by sub-MHz manifestations of their existence.
-- Bill Sloman, Nijmegen
"Dirk Bruere at NeoPax is a Nut Case "
** Most bench audio generators will go down to 1 Hz or less.Almost audio power amp can be made to work fine at 0.5 Hz by changing one or two small capacitors.
Fuckwit.
.... Phil
integration.
very robust.
Especially with audio transformers, you often have to wind your own. How often do you make your own capacitors or resistors ?
For signal levels higher than line levels, achieving at least 10 octaves (20 Hz .. 20 kHz) bandwidth can be quite a challenge.
Paul
Results would not be what you want, even if the coil driven transducer had a low roll-off..
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