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 Forum index » DIY Hardware and Software
SN76477's Little brother, the SN94281
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State Machine
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PostPosted: Tue Dec 12, 2006 6:57 pm    Post subject: SN76477's Little brother, the SN94281 Reply with quote  Mark this post and the followings unread

I was just taking a peek into my parts bin and I came across 3 of these SN94281 IC's. Cool It's basically a stripped down SN76477 but it got me wondering, can it's VCO be 1V/Octave controlled using the Thomas Henry SN Voice circuit exponential converter? It would seem to me that it could as I doubt that TI would have changed the basic design of the VCO from this chip to the 76477.

There is no Attack/Decay module, no envelope generator and no external noise clock or noise filter. and no envelope lock feature like the 76477. It's still a cool little chip!! Very Happy

I have to take a peek at the data sheet as I see an interesting pin "AUDIO IN" ... Hmmmm ....

Anyone else have these? What are your thoughts?

Bill


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sneakthief



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PostPosted: Tue Dec 12, 2006 9:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Check out this schematic and see how it compares to the original SN76477 project schematics:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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bugbrand



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PostPosted: Wed Dec 13, 2006 3:12 am    Post subject: Reply with quote  Mark this post and the followings unread

I just got hold of 4 of these (real cheap - it was a buynow ebay for 2 of them but I got sent 4!)

I've just done a PCB for basic test of the BeepBox schem - MikeFord asked me for this and then I located chips so I could do it myself. I made the PCBs yesterday, today I'll build, test & report!

The AudioIn, though, is just to get an audio signal in to the internal amp - no processing (I'm pretty sure..)

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shawn



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PostPosted: Wed Dec 13, 2006 8:25 am    Post subject: Reply with quote  Mark this post and the followings unread

I have one of those chips as well. In fact I have ANOTHER SN chip that is neither the 76477 or the 94281. I'll check my 'special' chips bins and find out what it is. I've been pondering what I could do with these chips.
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State Machine
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PostPosted: Wed Dec 13, 2006 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Check out this schematic and see how it compares to the original SN76477 project schematics:


OK, yes, I remember this schematic. Now I realize it's the 94281 Very Happy

Thanks ....
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bugbrand



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PostPosted: Wed Dec 13, 2006 4:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hmm, so I didn't really like the results too much of the straight-up BeepBox design --- but didn't have time to tweak and bend and go over the datasheet again......
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