Digital Tachometer

[Woodturner1]

I need a schematic for a digital tachometer that will use a photo-electric pickup and give a digital read-out of rpm's. [email protected]

[dacflyer]

you need a handheld unit??
i know hobby shops here have handheld units for sale..they use them on model engines to tune them,,just a thought <p>they operate via optical pick-up

[moldmaker]

ELECTRONIS NOW, DECEMBER 1999
HAS A TACOMETER SCHEMATIC THAT WORKS
LIKE A TIMING LIGHT, YOU SET THE STROBE
LIGHT UNTIL THE OBJECT STOPS MOVING
AND THATS YOUR SPEED.
GO TO YOUR LIBRARY OR LOCO COLLEGE
TO SEE IF THEY HAVE THAT ARTICAL
IF NOT EMAIL ME A FAX NUMBER AND I WILL
FAX IT TO YOU (I DONT HAVE A SCANNER)

[dacflyer]

strobe light tach ?
i cannot count that fast ...how does this work?
i am guessing once the strobe is in sync with the moving object...that there is also a built in counter in the strobe that detects the flashes? is that right?

[Edd]

Aside...dacflyer...de...jetflyer:
Strob-a-tac
Probably quite a variance from your familiar dealings with of hi intensity strobes ,at inter-second timed repetitions as are used on aircraft units or PD/Emergency units .
The strobe design circuitry as well as its power refresh is shifted towards attaining faster flash repetitions. The strobe is then driven by an adjustable freq osc/pulse generator. On the older units there was a front panel mounted potentiometer with a large dial and its 270 deg scale with the freq marked off in increments. Newer units have dig freq displays. The strobe tube typically had a rear reflector and a front lens in order to capture and concentrate max light energy forward, as light output energy dissipated operating at higher frequencies.
The observed object either required a definitive shaping..e.g… like a planes 2/3/4 prop elements configuration or spokes numbers on a wheel or blades on a fan. Or if undefined , one placed a white (contrasting?) paint /stick on marker on the timed unit.
One then would then point the strobe at the rotating object and the speed of the tac adjusted until the observed timing reference marker/shape slowly drifts into a freeze or drifts the other direction if the freq is shifted to far. Then the freq/speed is read from the dial scale. This procedure being good up to the kilohertz range of the units oscillator then one has to refer to 2nd or 3rd harmonic read out of duplicates or triplicates of the observed timing marker and then correlate to frequency/speed.<p>73's de Edd
[email protected] ....……..(Interstellar~~~~Warp~~~Speed)
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<p>[ November 30, 2004: Message edited by: Edd Whatley ]</p>

[Deal]

George, imagine you want to tack spindle speed of your lathe. I started with the homebrew tack issues back in 1981 when I built one of the first digital bikeometers (using those great old intersil ICM7224 IPL chips and hall effect sensors) and still have the original wirewraped prototype. One way you might go is with Harbor Freight part number 41727-2AFA - 60 dollars- 8004232567 photo sensor Tach that reads reflective tape. I know the tack issues (prop and generator speeds in boats) and even though I am twixt an tween about ordering cheap Chinese tools and instruments because we are digging our own economic and technological graves, I have to say that the electronic stuff from this source has worked. If you are thinking in terms of design and manufacture, I'd go with Parallax stamp stuff (they have some nice, proven schematics on their web site. Good luck with your spinning applications