Re: [CAD_CAM_EDM_DRO] r.p.m. kit??? / 4 digit under $20

Tony Jeffree wrote:

>
> If you use a pulse generator that gives 6 pulses per rev, then all you have
> to do is shift the decimal point one place to the right, rather than
> multiplying by 60. Use a 60PPR encoder, and it reads directly in RPM.
>

Tony:

That is a great observation! I just went to USDigitals encoder website
http://www.usdigital.com but didn't see any 60 PPR rotary encoders.

However, they have some 120 PPR (they call it 120 cpr, which is 480 count
in quadrature) encoders.

Prefaced by a divide-by-two chip, then, as you observed, the under-$20
frequency meter kit at http://www.qkits.com/serv/qkits/diy/pages/QK148.asp
would directly read out the 4 digit rpm.

Its too bad that encoder doesn't seem to be available with an index option,
which would enable the lathe threading capabilities on software such as
TurboCNC http://www.dakeng.com/turbo.htm

I do see a 360 PPR encoder with index available (1440 in quadrature),
and presumably using that with a divide-by-six chip would also enable
the direct readout of rpm.

Doug Fortune
http://www.cncKITS.com

























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