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DMM Tach. Add-On

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Bluechip:
Piccy of cct. boards..

General Idea   (R.P.M. x # Slots in Disc) / 60   = Frequency 

So assuming 4 Slots   in disk ..

131.3 Hz = 1969.5 RPM.  I got 1970. This is linear to ( as far as I checked, about every 500 RPM.) to 633.3 Hz ie. 9500 RPM.

Nice Chip,  thanks to National Semiconductor Inc.

Other board is a Xtal cmos Oscillator / divider for calibration.



http://s359.photobucket.com/albums/oo31/Bluechip_mech/?action=view&current=013.jpg

dave

Darren:
This site just gets more and more interesting by the day  :thumbup:

Bluechip:
What? Want more?  Good grief, world is awash with strange folk ..  thought I was unique .

OK. If anyone might like the cct. diags etc. will do 'em. 

Will re-draw originals to ensure correct, I have a habit of modding circuits and not updating record.

dave

Darren:
nowt stranger than you'll find one here, just ask my missus  :lol:

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