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Old 22nd January 2005, 09:11 PM   #1
Join Date: Jan 2005
Default Alternative usage for LM3875

Hello! I was sitting here half bored until i came up with a idea, why not try to use them as a VSD (Variable Speed Drive) So i took a big transformer and hooked a secondary to the speaker outs on the 3875īs and the 230 primary to a fan and a motor. This is the result: <-- 125Hz on the fas and over 600Hz on the motor using a function generator on the computer and the cassette deck as preamp. There is sound on both videos.
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Old 22nd January 2005, 10:45 PM   #2
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Hi Tekko,

Could you not pump those AVI's into some encoder and make it wmv or something...this way it takes 10 minites to download!


I converted your Video7.avi to video7.wmv from 27mb to 2 mb...quality of the wmw is lower ofcourse
If you can see the speaker cone's not hifi.
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Old 23rd January 2005, 01:53 AM   #3
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I had an idea about using a +12V audio amp chip (TDA7350,or many others.) as a driver for a small 12V-120/240Vac inverter.Add another chip with a nice 50/60hz sine wave,and suitable power trannie(wired "backwards" for step-up)and you're set.Doesn't seem too complicated.Add a couple pots to set the freq and level (voltage out),maybe replace them with fixed reistors after you get it all dialed in.
You wouldn't be able to get a whole lot of power,maybe 25W? (unless you could parallel the chips?) but it might be handy for recharging phones,pda's,laptops?,running a small CFL light,etc from 12V sources.
But one bonus is that it has a sinewave output,none of that "modified squarewave" stuff.
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Old 23rd January 2005, 01:57 AM   #4
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read this:

OP-AMP based car amp power supply

I had asked the same question before.
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Old 23rd January 2005, 08:55 AM   #5
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This is controlled via the computers soundcard and a function generator. I could encode them but i donīt have a encoder.
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