Thread: Tacho Update

Got some time at the weekend (the friend with benefits was away) the Hall sensor did not work out, as its output voltage (200 mV) was too low to drive the MX 019 P.C.B. and I couldn't be bothered dicking around adding amplifier stages. A rat through the junk bins uncovered a Sick reflective sensor and mounting bracket, I used this with the sector plate & put a piece of white reflective Scotchlite behind it. The output voltage of the Sick sensor was a bit high at 12 volts so ran it through a 5 volt regulator. A bit of fiddling around to get the angle and sensitivity right and it works a treat. The cost of parts (less the sensor) ran to about $ 65.00. Another triumph of bush electronics.
Regards,
Martin
P.S the right hand digit in the photos appears very dull, in reality it is barely noticeable

That came up nice and clean looking It still amazes me a lathe that old is in so good condition.
What rpm will it count up to?

Dave

G'Day Dave,
The display will read up to 6000 R.P.M. Since fitting the tacho I have been able to calibrate the motor speed control board and have a continuous range from 30 to 1200 R.P.M. The lathe is actually new, it was in storage for 20 years.
Regards,
Martin

Hi Martin,

Nice work, I like the mounting bracket for the photocell, very clean, lots of adjustment.

If I recall, your lathe has a DC variable speed drive? so a tacho is a very useful addition.
No more guessing what the RPM actually is.

Not sure what the response time of the photocell is, but with 10 pulses per rev, the PE response time will probably be the limiting factor in what maximum speed can be sensed.

At 6000 rpm. that's 100 Hz x 10 ppr == 1Khz, == 1ms the PE would need to switch on/off in 1ms.

Unlikely you would ever go that fast of course

Regards
Ray

Originally Posted by toolman49

G'Day Dave,
The display will read up to 6000 R.P.M. Since fitting the tacho I have been able to calibrate the motor speed control board and have a continuous range from 30 to 1200 R.P.M. The lathe is actually new, it was in storage for 20 years.
Regards,
Martin

Yes I read you original thread on the lathe, the preservative kept it in good nick.

Dave

But it was a bitch of a job getting it off.
Regards,
Martin

Hi Toolman49,
Nice job your doing on the Lathe modifications.
If you get problems with the Sick PE have a look at the Sunx PM53 PE, its relatively cheap and works very well for pulse counting in tacho applications.
I have recommended it for years and always had positive reports back.

Regards,
Keith.