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  1. #1
    Tom's Avatar
    Location unknown. Last Activity: 30-11-2016 Has been a member for 7-8 years. Has a total post count of 172. Referred 1 members to the community.
    Hello all,
    It's been a while since I was last here...

    I'm in a world of hurt trying to wire up some form of spindle speed detection for a lathe.

    I've got some Darlington photointerruptors (KTIR0121DS) which I think are the right thing for the job. I want to power them from a 5V supply, and sense the outputs on inputs to a parallel port (the PCPPS breakout board from DIYCNC).

    Can anyone suggest the right circuit and resistor values for this?
    I've made 3 versions now, and all of them seemed to work OK (swing from 0.6V to 5V when interrupted) until connected to the parallel port inputs. Once connected though the voltages were different, and only moved around 0.2V when interrupted, which is not enough to change the inputs.

    I'm clearly doing something wrong, but after 3 attempts to start from scratch and recalculate, I haven't got things running...

    Can anyone help?

  2. #2
    Tom's Avatar
    Location unknown. Last Activity: 30-11-2016 Has been a member for 7-8 years. Has a total post count of 172. Referred 1 members to the community.
    Here's the circuit I've arrived at. The resistance values are 100 ohm for the led, and 6800 ohm for the sensor. The signal gets connected to the parallel port.

    What am I doing wrong?:thumbup:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  3. #3
    Tom's Avatar
    Location unknown. Last Activity: 30-11-2016 Has been a member for 7-8 years. Has a total post count of 172. Referred 1 members to the community.
    Here's a link to the datasheet:

    KTIR0121DS datasheet pdf datenblatt - Kingbright Corporation - PHOTO-INTERRUPTER ::: ALLDATASHEET :::

    Any pointers would be massively helpful...

  4. #4
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    have a look here.

    Need Encoder for threading

  5. #5
    Tom's Avatar
    Location unknown. Last Activity: 30-11-2016 Has been a member for 7-8 years. Has a total post count of 172. Referred 1 members to the community.
    Thanks for that. I've bitten the bullet and ordered some Optek OPB916B. It seems the processing circuitry is included, so should make life easier...

  6. #6
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    cncdoctor makes an index pulse board which is perfect for this, but last time i looked he was out of stock.

  7. #7
    Tom's Avatar
    Location unknown. Last Activity: 30-11-2016 Has been a member for 7-8 years. Has a total post count of 172. Referred 1 members to the community.
    I recon those bits will do it... The cncdoctor board looks the business, but in the fullness of time I'm going to want spindle index, spindle pulse, x home and z home, so i was trying to do it simply and cheaply.

    Back in the day I'd have sorted that KTIR0121 circuit in my sleep. All forgotten!

  8. #8
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    i've used his board and it works well, but all you need is the sensor and the correct limiting resistor.

  9. #9
    Tom's Avatar
    Location unknown. Last Activity: 30-11-2016 Has been a member for 7-8 years. Has a total post count of 172. Referred 1 members to the community.
    Well, that was remarkably easy! 3 resistors, 3 sensors, a case, and an ethernet socket to carry the signals back to the control box. All working happily.

    The only problem is I fried 2 inputs on the bob during my misadventures. Are there any options out there other than the diycnc bobs?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  10. #10
    Worried about saying the obvious.... but have you ever used an Arduino? If I were doing what your doing; my initial tool would be an Arduino...

    Apologies in advance if that is a useless comment.

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