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laser mirror motor nightmare

 
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gelo
HG Junior


Joined: 01 Feb 2007
Posts: 20

PostPosted: Sat Apr 14, 2007 3:08 pm    Post subject: laser mirror motor nightmare Reply with quote

yo again, im having serious trouble with the amp this time. i got me an op amp as i said before i think and im having trouble amplifying the signal, anyone know of a simple amplifying circuit for an AC signal?

i have a 5 volt power supply and a 600 mV audio signal. all i need is a digram with Rf and the other resistor and which ground/earth goes to which cos all im getting is one mirror rotating slowly and the other doing nothing...

plz move if its in the wrong place, i wont complain.
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Alan
Site Admin


Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Sun Apr 15, 2007 2:33 am    Post subject: Reply with quote

There are lots of amp circuits on this page that might help:
http://www.hobbyprojects.com/A/audio.html
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gelo
HG Junior


Joined: 01 Feb 2007
Posts: 20

PostPosted: Sun Apr 15, 2007 3:40 am    Post subject: Reply with quote

sorry alan they dont work.

well the low power ones anyway...

was just wondering with the ground for both the input and output do they go to the ground for the supply to op amp or are they completely separate?

just wondering if i got my connections wrong or not cos it seams that i amplify on the inverted input and then it just works as a voltage follower on the non inverting input
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Nginuity
HG Ruler


Joined: 13 Nov 2006
Posts: 224
Location: Dallas, Texas

PostPosted: Sun Apr 15, 2007 11:47 am    Post subject: Reply with quote

They share the same ground....

Also, see is you are getting correct voltage after the first op amp. If that figure is a negative value, then you have the inputs switched. If you get nothing, something else is wrong.

That second op amp without gain usually just functions to bring the total resistance of the output down. Using an op amp usually makes the resistance very high, and a non amplifying second op amp is used to bring it back down.
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gelo
HG Junior


Joined: 01 Feb 2007
Posts: 20

PostPosted: Sun Apr 15, 2007 12:08 pm    Post subject: Reply with quote

sorry should of said before, the op amp i have has two exactly the same channels
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