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Author Topic: opto isolation of audio  (Read 4289 times)
M3DGQ
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Posts: 2




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« on: December 05, 2002, 04:40:16 PM »

can anyone help with some circuit design
i need to isolate sound from my sound card to the rig useing opto isolators not transformers how do i do this

cheers peter m1dgq /m3dgq
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NB6Z
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« Reply #1 on: December 06, 2002, 01:41:14 PM »

Find it at http://www.qsl.net/wm2u/psk31.html
The opto isolation is for the RS232 PTT line only, not the sound card audio. I am curious; can you tell me why you must opto isolate this line instead of using a single transistor switch? Opto coupling is generally used for High Voltage isolation, not RFI issues.


Griff.
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NB6Z
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« Reply #2 on: December 06, 2002, 02:14:22 PM »

Peter,
If you want to pursue a sound card audio opto isolation design, I can suggest the Siemens part IL300 or TI's TIL300 opto device for linear applications.
http://www-s.ti.com/sc/psheets/soes019a/soes019a.pdf
They sell for $1.54 each per 1000 piece price.
This is a true photo diode output devive, so you will need op-amps to drive the inputs and outputs to achieve the levels you want. (I hope you are an EE ;-)

GL Griff.
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W4CNG
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« Reply #3 on: December 09, 2002, 10:48:54 PM »

You isolate PTT via opto-isolators (plus resistors, ect).  You isolate Audio with transformers (matched for your load, plus resistors).  Unless your wallet is well lined, you will not do audio with Opto-Isolators (have not seen this done).  I have boxes to match all of my PC-Radio's with resistors and 1 transistor to key the radio from the computer, one for laptop, one for PC Box. Total cost with a well stocked parts box is $20 each max..
Good Luck Steve W4CNG
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IC8POF
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« Reply #4 on: December 14, 2002, 12:47:41 PM »

Ciao Peter, maybe you mean isolating the SBlaster in and out . You accomplish that via 2 small audio tranformators and some switches to disconnect sb-audio from the mic audio.
If it is so let me know and I will scanner-ize a little plan taken from the german CQ-DL magazine.
73s de IC8POF
WWW.QSL.NET/IC8POF
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DD3LY
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Posts: 25




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« Reply #5 on: December 06, 2004, 01:59:18 AM »

The best circuit I know uses a linear optocoupler as NB6Z mentioned. You may take a look at the following two links: http://www.elv-downloads.de/service/manuals/18986_Optischer_Trennverstaerker/189-86.htm
http://www.elv-downloads.de/service/manuals/OTV/369-01.htm
There you can download two different (german written) building manuals for kits of two different optoisolation amplifiers. You can order them at www.elv.de but I think homebrewing is better. These manuals contain the circuits. These optoisolators are linearized by operational amplifiers and have a bandwidth of 20kHz or 40kHz depending on the circuit. What you need to build an optoisolator for both directions are two of the small kits (not the stereo version) or two LM358, two IL300 and just some few other parts from your junkbox.
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