[Noisebridge-discuss] Dynamo Regulator Help Needed
jim
jim at well.com
Sun Jul 21 21:43:25 UTC 2013
A different approach, assuming AC from the
"dynamo", is to feed it to a transformer,
even a 1-1 tranny, and feed the audio amp
with the tranny secondary (with recitfier
and conditioning circuitry between the
secondary and the amp's power input stage).
On Sun, 2013-07-21 at 14:24 -0700, Dennis Gentry wrote:
> Maybe the simplest thing is to get a speaker that can directly handle
> the amount of power that the dynamo can put out, and get rid of the
> audio amp.
>
>
> Barring that, do you have a series capacitor (say 100 uF) between the
> dynamo output and the audio amp input to block DC? You shouldn't be
> feeding any constant (DC) current into the audio amp, lest it blow
> up.
>
>
> Another way to get it to blow up would be to feed the audio amp (or
> the aforementioned 100 uF cap) too high a voltage. Instead, load the
> dynamo with a (relatively high valued so it doesn't get hot) resistor
> across its terminals to keep the voltage in a sane range, then use a
> voltage divider to bring that maximum output voltage down to whatever
> your audio amp can handle.
>
> Less critical issues: Do you want it to get louder as (the dynamo
> rotates faster and) it gets higher pitched, or do you want to keep the
> volume somewhat constant? You might find that the dynamo will make a
> lot more power at high RPMs, so when you scale down the voltage as
> needed to not blow things up, the audio might not be audible at low
> RPMs without amplification. (This is easy to fix, if it is what you
> want.)
>
>
> Hope this helps a bit!
> Dennis
> P.S. Anyone know a good way to quickly draw and send circuit diagrams
> in email?
>
>
>
> On Sun, Jul 21, 2013 at 11:14 AM, Johny Radio <johnyradio at gmail.com>
> wrote:
> Hello
>
> Can anyone suggest how to limit the voltage and/or current
> coming out of a dynamo, before audio amp?
>
> Actually, I'm not sure if this is a dynamo or alternator-- i'm
> cranking the shaft of a DC motor, and tapping the electric
> terminals. I'm trying to amplify the AC sine coming off the
> terminals through a loudspeaker.
>
> It basically works-- i can hear the motor oscillation from the
> speaker driver, which is my goal. But i've blown two audio
> amplifiers doing this. The motor is not large (about 2" long,
> 1" diameter), but i'm spinning it at thousands of cycles per
> second. According to one article, as frequency increases, so
> does output current.
>
> I'm not sure if the issue is too much current or too much
> voltage. i believe i'm not getting clipping, so i suspect the
> problem is too much current. A couple fat resistors in series
> with one of the terminals did not prevent the amp from
> blowing. Also, the speaker driver heaves, which suggests to me
> either an impedance issue, grounding issue, or low-frequency
> content.
>
> I've found a couple ways of possibly handling too much
> current, using circuits mostly designed for charging batteries
> off a generator. I found solutions based on BJT transistors,
> CMOS, power regulator chips, or diodes. Links below.
>
> I'm not charging batteries, so i wonder if i can eliminate the
> reverse current protection? Actually, the motor no longer
> spins when i apply voltage to it's terminals, so i think i
> blew the motor in some way. Strangely, it still outputs a
> sinewave when i turn it's crank. So maybe the reverse current
> protection IS needed.
>
> One solution employs a pair of diodes, wired back to back,
> between the motor terminals (i think). This is intended to
> clip the voltage, resulting in a square wave. This solution is
> not desirable, because i want to preserve the sine shape
> coming off the DC motor.
>
> How can I limit current (or is it voltage?), without squaring
> the original sinewave? As always, seeking a lowest-parts-count
> solution, passive if possible. Any help is appreciated!
>
> http://islandcastaway.com/alternator-secrets/
> http://www.instructables.com/id/Power-LED-s---simplest-light-with-constant-current/?ALLSTEPS
> http://goo.gl/MG4mF
> http://forum.allaboutcircuits.com/showpost.php?p=331463&postcount=52
> http://ludens.cl/Electron/dynareg/dynareg.htm
>
> --
>
> Johny Radio
>
> Stick It In Your Ear!
>
>
>
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