PSN-L Email List Message

Subject: Re: Verticle Seismometer with Feedback, Transducer Question
From: ChrisAtUpw@.......
Date: Sat, 13 Sep 2008 00:07:49 EDT


In a message dated 2008/09/13, gel@................. writes:

> I=E2=80=99m collecting parts for a vertical seismometer and intend to use=20=
feedback.=20
> The feedback transducer I have is from a 12=E2=80=9D hi-fi speaker. I have=
 separated=20
> the voice-coil and magnet and now wondering what sort of current capabilit=
y=20
> do I need to specify for the voice-coil driver. Certainly this voice-coil=20
> must have high power capacity when it was used as a speaker. DC resistance=
 is 7=20
> ohms. If you assume a 20 watt speaker and 7 ohm resistance, then RMS curre=
nt=20
> would be 1.7 amp. Has anyone built a transducer driver with this sort of=20
> capability.=20

Hi Gary,

       Check with Sean Morrissey's website.
       The problem that you will have using a speaker coil is that the arm=20
moves in an arc of a circle, but the coil has only a few thous of an inch=20
clearance. It may be a bit difficult to keep the coil from rubbing on the=20
polepieces.
       It is more usual to wind a coil of about 100 Ohms.

       Regards,

       Chris Chapman  =20
In a me=
ssage dated 2008/09/13, gel@................. writes:

I=E2=80=99m collecting parts fo= r a vertical seismometer and intend to use feedback. The feedback transducer= I have is from a 12=E2=80=9D hi-fi speaker. I have separated the voice-coil= and magnet and now wondering what sort of current capability do I need to s= pecify for the voice-coil driver. Certainly this voice-coil must have high p= ower capacity when it was used as a speaker. DC resistance is 7 ohms. If you= assume a 20 watt speaker and 7 ohm resistance, then RMS current would be 1.= 7 amp. Has anyone built a transducer driver with this sort of capability.

Hi Gary,

       Check with Sean Morrissey's website.        The problem that you will have using a=20= speaker coil is that the arm moves in an arc of a circle, but the coil has o= nly a few thous of an inch clearance. It may be a bit difficult to keep the=20= coil from rubbing on the polepieces.
       It is more usual to wind a coil of abou= t 100 Ohms.

       Regards,

       Chris Chapman

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