Denford Software & Machines

Hi all, wondered if anyone can help. I have an easiturn fitted with the original spindle speed controller. It stopped working the other week so i bought a new photo interupter ( rs 304-560) and had it soldered to the control board. it now works but seems to be out of calibration. i.e when its running at a 1000 rpm it only reads 100 rpm. does anyone know if you can calibrate these control boards.

Cheers

Steve

I'm not sure how you'd be able to calibrate it if it actually measures a pulse every revolution ?
ie, every on/off counted by the control is one rev of the spindle
The only thing I could think is that the it's missing the on/off pulse and only seeing it once in every ten revs
Maybe the disc passing through it needs altering, reshaping or moving ?

stevewatson wrote:...it now works but seems to be out of calibration. i.e when its running at a 1000 rpm it only reads 100 rpm.

Can you give us a bit more info. and some pictures?

Is the interrupter a direct replacement for the one you had? Does the logic work the same (i.e. light passing = high output; light blocked = low output. Alternatively, light passing = low output; light blocked = high output).

What does the encoder wheel look like? Has it a single row with a single slit? A single row with multiple slits? Has it a double row, one with a single slit and the other with multiple slits?

Is the interrupter correctly located relative to the slot(s)?

What does the PCB that holds the photo-interrupter look like? Has it space for one or two interrupters?

Put a volt meter on the output and rotate the spindle slowly by hand and understand what it is doing.

thanks for your replys. i ve tried moving the photo interupter and the rpm reading does vary up and down when moved but its still not representing the correct rpm wherever i seem to move it. i will try the outputs with a volt meter and see what i can find out. It seems to only be counting some of the holes in circular board and not all. the photo interupter is a direct replacement. I ll take some photos tomorrow and post them.

Cheers Steve

The only true way to set these up acuratley is to use an osiloscope. If you then adjust the sensor you will get an even waveforem as it reads every hole. The sensor will probably not give sharp edges and if it is reading slightly off centre to the holes then the on time is significantly reduced and may not reach the threshold of switching so as to be counted.