noise: [Noisebridge-discuss] re Dynamo Regulator Help

jim jim at well.com
Mon Jul 22 03:52:54 UTC 2013


there's the possibility of an oscillation 
varying around a DC voltage, for instance, 
a voltage that varies from +2 to +10 Volts 
could be seen as an 8VAC riding on a 2VDC 
level. Couple that as input to a capacitor 
or a transformer and you'll pass only the 
AC component. 



On Sun, 2013-07-21 at 17:44 -0700, Johny Radio wrote:
> Henner Zeller h.zeller at acm.org 
> Sun Jul 21 22:07:55 UTC 2013 wrote
> 
> 
> >>If it is a DC motor, it will output DC with a bit of noise. 
> --it clearly outputs an oscillation. Isn't an oscillation always AC,
> even if it's offset above zero, and never goes negative?
> 
> 
> >>60000 RPM, which is way higher than what typical small motors
> usually
> --it takes 30+ volts on the power supply of the OTHER DC motor (which
> is used to spin the shaft on the "oscillator" motor)
> 
> 
> >>Before connecting to the amplifier, use the multimeter to measure
> that the AC voltage is in the order of 1V, which is a typical input.
> --cool, will try
> 
> 
> >>It is the voltage or the DC part of the voltage that is killing your
> amp.
> --i did try a 100uf series cap on one of the terminals. Did not
> protect the amp. 
> 
> 
> >>If you voltage is _way_ to high (which I suspect is happening here),
> then you can blow the input stage, because you send too much current
> through
> --um, current? or voltage?
> 
> 
> >> the resistor you have 'on the outside' forms a voltage divider with
> the input impedance. If they are in about the same order of magnitude,
> you get half the input voltage.
> --then shouldn't the series resistors i used give me significant
> overdrive protection? They seemed to have no affect. 
> 
> 
> >>It does sound you operated the motor way out of its specs.
> --in what way?
> 
> 
> >>a DC motor does _not_ generate a sine wave, at best it returns a
> wave that you would get as the result of rectifying a sine wave; that
> is what the commutator is for. If it is an AC motor, then you get a
> sine wave.
> --on the scope, it sure looks sine-like. But also weird. 
> 
> thanks
> -- 
> 
> Johny Radio
> 
> Stick It In Your Ear!
> 
> 
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