Re: [CAD_CAM_EDM_DRO] Tach Sensor

On Mon, 9 Jun 2003 00:25:23 -0400, you wrote:

>I could use a little help with a tach sensor.
>
>I have a Red Lion Controls Cub5 Counter/Rate Indicator that I would like to
>use for a spindle tach on my Dyna-Myte mill
>http://www.redlion-controls.com/products/doc/01012.pdf
>
>The sensor trigger levels are
>Vih: 4.2V min
>Vil: .5V Max
>V Max: 28VDC
>
>Current sinking: internal 40KOhms typical pulled up to 5V
>
>Ok, I assume the Vih is the min voltage pulse required to trigger the
>counter. Red Lion sells a magnetic pickup as an option for the sensor. Could
>I simply mount 2 magnets on the spindle pulley 180 degrees apart (for
>balance) and a coil of wire wrapped around a steel shank, placed close to
>the magnets as a pickup, and if so, will that generate somewhat close to the
>voltage required to trigger this thing? Will some sort of pulse shaping be
>necessary to clean up the pulses?

The specs are essentially TTL logic specs for an input, except that it
can withstand 28 volts.

You might want to look into hall effect sensors. They can be had with
TTL output levels, and run off 5 volts. They're made for just this
kind of application.

A coil would not necessarily work as well.

>
>If I will need an amp or pulse shaper for the above, should I just use a
>photo reflective or interruptor type sensor to put out a 5V pulse to the
>counter? Is there one, that anyone knows about, that requires no external
>circuitry, just Vin and ground and outputs the required pulses? Photo
>reflective would be prefered. Price is no object as long as it's cheap.
>

Photo reflective is easy enough.

However, I've got many photo interruptors that run off IR, are
straight line, and generate a good TTL level pulse...

Basically, feed the LED 5 volts through a 470 ohm resistor, ground the
- lead of the sensor, and put the + lead of the sensor to the input...
adding a resistor from the + sensor line to 5 volts would be a good
idea... 4.7 K would be a decent value... 1K would probably be about
the limit...

Harvey

>Thanks from the electronically challenged.
>
>Bill
>
>