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  1. #161
    Aha, the same style that I have also.

    Inputs:
    [I'll correct the 101 mistakes in the following para, below... ignore the stuff in italics - included as a reminder for the crap I typed this morning]
    So, that addresses the onto-isolated inputs. However, the design of that board presents the cathode of the onto-isolator via a 1k resistor to the input pin. The associated anode is wired to the on-board +5V supply. So, shorting the input to ground will activate the otto-isolator. Similarly, having an NPN drive to the pin *should* activate the opto-isolator, however, you have to consider a couple of issues: With the NPN drive OFF, you need a pull-up (or the NPN sensor must have a pull-up). If you intend to use 24V signalling this means that, with the sensor off, and the sensor output pulled to 24V, that you're reverse-biasing the LED fragment in the opto-isolator. My board has EL817 onto-isolators, which have a typical maximum reverse voltage of 6V. Assuming that your 24V and 5V supplies have a common ground that gives you a reverse-bias of 19V across the LED, which exceeds the data sheet value substantially.

    5V switching (or 6V if that's the lowest supported by the sensor) is completely do-able.Above 11V is giving you problems. There are ways around all this - let me know if you want to investigate these options.



    So, that addresses the opto-isolated inputs. However, the design of that board presents the cathode of the opto-isolator via a 1k resistor to the respective input pin. The associated anode is wired to the on-board regulated 10V supply used for the PWM output (and fed from the 12-24V input). So, shorting the input to ground will activate the opto-isolator. Similarly, having an NPN drive to the pin *should* activate the opto-isolator, however, if the sensor has a pull-up (or you've added a pull-up) you have to consider a one issue: With the NPN drive OFF and with a pull-up resistor and if you intend to use 24V signalling this means that, with the sensor off, and the sensor output pulled to 24V, that you're reverse-biasing the LED fragment in the opto-isolator. My board has Liteon LTV-817B opto-isolators, which have a maximum reverse voltage of 6V. Assuming that your 24V supply for the sensor is the same as the feed into the BoB, or otherwise have a common ground that gives you a reverse-bias of 14V across the LED, which exceeds the data sheet value substantially.

    This is only an issue if you have a pull-up as part of the design (or part of the sensor). If not, then it's not an issue, but be aware although you're driving the BoB at 12-24V, the actual switching is regulated to 10V. Don't inject 24V into the inputs of this board (worst case scenario: you'll fry the opto-isolator, and possibly the onboard regulator - but protect the UCx00 controller).

    It also means that the inputs are dependent on the 12-24V supply, even if you don't intend to use the PWM output. The logic on the board is dependent on the 5V supply, as are the stepper motor outputs.



    Outputs:
    Just remember the resistor-bank that you asked about - your drive to the stepper drivers is still 5V signalling and requires no additional resistors for current limiting. You need to source a 5V supply for the BoB, as well.



    The more that I look at BoBs, the more I'm inclined to design my own extension BoB boards for the UCx00 range of controllers that give complete galvanic isolation to the input circuitry.


    EDIT: Since the visual inspection, I've now metered the board and I'm happy with the info above.

    I'm in the same position of trying to understand the reliable interfacing to a UCx00, although my own apathy is slowing my build.
    Last edited by Doddy; 01-06-2018 at 02:05 PM.

  2. #162
    Quote Originally Posted by Doddy View Post
    Aha, the same style that I have also.

    Inputs:
    [I'll correct the 101 mistakes in the following para, below... ignore the stuff in italics - included as a reminder for the crap I typed this morning]
    So, that addresses the onto-isolated inputs. However, the design of that board presents the cathode of the onto-isolator via a 1k resistor to the input pin. The associated anode is wired to the on-board +5V supply. So, shorting the input to ground will activate the otto-isolator. Similarly, having an NPN drive to the pin *should* activate the opto-isolator, however, you have to consider a couple of issues: With the NPN drive OFF, you need a pull-up (or the NPN sensor must have a pull-up). If you intend to use 24V signalling this means that, with the sensor off, and the sensor output pulled to 24V, that you're reverse-biasing the LED fragment in the opto-isolator. My board has EL817 onto-isolators, which have a typical maximum reverse voltage of 6V. Assuming that your 24V and 5V supplies have a common ground that gives you a reverse-bias of 19V across the LED, which exceeds the data sheet value substantially.

    5V switching (or 6V if that's the lowest supported by the sensor) is completely do-able.Above 11V is giving you problems. There are ways around all this - let me know if you want to investigate these options.



    So, that addresses the opto-isolated inputs. However, the design of that board presents the cathode of the opto-isolator via a 1k resistor to the respective input pin. The associated anode is wired to the on-board regulated 10V supply used for the PWM output (and fed from the 12-24V input). So, shorting the input to ground will activate the opto-isolator. Similarly, having an NPN drive to the pin *should* activate the opto-isolator, however, if the sensor has a pull-up (or you've added a pull-up) you have to consider a one issue: With the NPN drive OFF and with a pull-up resistor and if you intend to use 24V signalling this means that, with the sensor off, and the sensor output pulled to 24V, that you're reverse-biasing the LED fragment in the opto-isolator. My board has Liteon LTV-817B opto-isolators, which have a maximum reverse voltage of 6V. Assuming that your 24V supply for the sensor is the same as the feed into the BoB, or otherwise have a common ground that gives you a reverse-bias of 14V across the LED, which exceeds the data sheet value substantially.

    This is only an issue if you have a pull-up as part of the design (or part of the sensor). If not, then it's not an issue, but be aware although you're driving the BoB at 12-24V, the actual switching is regulated to 10V. Don't inject 24V into the inputs of this board (worst case scenario: you'll fry the opto-isolator, and possibly the onboard regulator - but protect the UCx00 controller).

    It also means that the inputs are dependent on the 12-24V supply, even if you don't intend to use the PWM output. The logic on the board is dependent on the 5V supply, as are the stepper motor outputs.



    Outputs:
    Just remember the resistor-bank that you asked about - your drive to the stepper drivers is still 5V signalling and requires no additional resistors for current limiting. You need to source a 5V supply for the BoB, as well.



    The more that I look at BoBs, the more I'm inclined to design my own extension BoB boards for the UCx00 range of controllers that give complete galvanic isolation to the input circuitry.


    EDIT: Since the visual inspection, I've now metered the board and I'm happy with the info above.

    I'm in the same position of trying to understand the reliable interfacing to a UCx00, although my own apathy is slowing my build.


    Ok Doddy,

    I did some testing on my backup bob :-).

    Input pins have a 1k ohm inline onboard resistor like yours.

    Test 1
    Put a 12vdc psu on the bob.
    Input Pins read 9.3 volts vs PSU ground/ input pin ground

    test 2
    Put a 24vdc psu on the bob.
    Input Pins read 9.3 volts vs PSU ground/ input pin ground

    Input pin output +9.3 voltage vs psu + 24vdc does not give a reading on the dvm.
    So there is some type of voltage regulator on the inputs circuit.


    opto`s : 1024 718B
    looks like this data sheet is the right one.
    http://www.everlight.com/file/ProductFile/EL817.pdf

    Test 3
    I tested my 6-36 vdc NPN proximity switches in 24vdc and 12vdc situation
    Hooked up a 4.7 k output load on black vs blue wire.
    this to test inline resistance of the proximity switch by voltage divider calculation.

    It looks like i have +/- 9.4k inline resistance in the output circuit of the proximity switch.

    http://www.ekt2.com/pdf/14_PROXIMITY_INDUCTIVE__8BX.pdf




    Do you feel i can there for not go past 12 vdc to protect the opto`s against :
    24volts PSU - 9.3volts input pin voltage = 13.7 volt reverse ?




    Maybe we are trying to solve a non problem, please look at line 3 and tell me what you think.



    Grtz Bert.






    Feature:

    1. Fully support control via parallel port, such as MACH3,etc.

    2. USB power supply and external power supply are seperate for safety.

    3. External power supply input: 12-24V. Equiped with anti-reverse connection function.

    4. All input signal will be isolated by optical coupler for further connection with emergency stop, tool setter, limit, ect for PC saftey.

    5. One relay output port for control spindle on/off. The output interface. is P17.

    6. One 0-10V analog voltage output port for control of inverter that has relative analog interface,and for control of spinle speed. The output interface is P1.

    7. If all 17 interfaces are activated, drivers equipped with optical coupler can be controled and 5 axis stepper motor can be controled.

    8. As PWM output, P1 can control spindle speed regulator that is equipped with optical coupler.

    9. Connection with 5V input drivers that has common cathode or anode is supported.
    Last edited by driftspin; 02-06-2018 at 05:25 PM.

  3. #163
    Quote Originally Posted by driftspin View Post
    So there is some type of voltage regulator on the inputs circuit.
    Agreed - our results tally.


    If the 817 is preceded with an italic "L", then its the Liteon LVT-817. The 1024 is just the date-code. These are all pretty much the same.


    Quote Originally Posted by driftspin View Post
    I tested my 6-36 vdc NPN proximity switches in 24vdc and 12vdc situation
    Hooked up a 4.7 k output load on black vs blue wire.
    this to test inline resistance of the proximity switch by voltage divider calculation.

    It looks like i have +/- 9.4k inline resistance in the output circuit of the proximity switch.

    http://www.ekt2.com/pdf/14_PROXIMITY_INDUCTIVE__8BX.pdf
    You don't say if the sensor is On or Off. What's the actual voltage with 24V applied across the supply, measured with a 4k7 pull-up, in both On and Off states? (I'll measure mine in the morning anyway). I'd expect the output voltage to be sat at 24V "Off" and near-as-dammit 0V "On".

    Quote Originally Posted by driftspin View Post
    Do you feel i can there for not go past 12 vdc to protect the opto`s against :
    24volts PSU - 9.3volts input pin voltage = 13.7 volt reverse ?

    Maybe we are trying to solve a non problem, please look at line 3 and tell me what you think.
    It becomes a non-problem provided that there are no pull-ups to the supply voltage to the sensor. Once you have the sensor input floating to 24V (which you'll only have with a pull-up, for example if you wanted a 24V control circuit) then you're breaking the spec on the data sheet, and will likely damage the optocoupler.


    Quote Originally Posted by driftspin View Post

    3. External power supply input: 12-24V. Equiped with anti-reverse connection function.
    I simply read that that there's reverse-polarity protection on (or around) the LM317 regulator. There is nothing on the optos to protect them (this would be an easy mod to the board to support 24V signalling).

    I do think this is a non-problem by avoiding 24V switching levels.

  4. #164
    Okay, a nice Sunday experiment.

    With reference to https://www.renesas.com/en-eu/produc...tandard-p.html - which discusses the effect of reverse-biasing an opto-coupler (section 1.5).

    I've hooked up a brand-new 4n25 opto-coupler, 1K between anode and +10V, cathode connected to either 0V (opto = on) or through a 10k resistor to 24V (opto = off, reverse biased, simulating the sensor behaviour). Collector to +10V, emitter through a 1k to ground. DVM across emitter and ground.

    With the cathode connected to 0V (on), the voltage at the emitter raises from 0.0 to 9.06V.

    Now, I connect the cathode to the 24V supply via the 10k resistor (simulating the sensor internal pull-up of 10k). Predictably, the emitter voltage drops to 0V as the opto-coupler turns off.

    So, the real test - leave like that for 5 minutes, then disconnect the 24V supply and ground the cathode.

    Result - emitter voltage rises to 9.06V

    Conclusion - for a short-duration (5 minute) exposure to 24V (and a reverse bias of 14V) the performance of the opto isolator is not changed.

    However, measuring the voltage across the 10k gives 0V (i.e. no voltage drop - no current flow) - the voltage hasn't reached the avalanche voltage of the opto's LED.

    Since then, I've added in a second PSU giving me a range upto 60V, in place of the 24V supply. Cranking the voltage up it was evident that the avalanche region of the LED in the opto was around 50V. Removing the 50V showed an emitter voltage of 9.01V (a 0.05V reduction from previous). Replacing the 10K resistor with a 2.2k resistor (to increase the current flow during the reverse-biasing), and the emitter voltage dropped to 8.84V (further degeneration). Note, this effect does appear to be permanent, but not increasing (in the 5-10 minutes I waited).

    So, what do I think? Reading random articles on the internet does suggest that reverse-biasing the LED will result in a deterioration of performance over a period of years. The article above suggests that even short duration reverse biasing can result in deterioration.

    However, the avalanche voltage may be substantially higher than the datasheet (clearly you can expect the opto-isolator to tolerate a 6V reverse bias without damage - but the actual headroom that you have between that and the actual avalanche voltage is unknown, and likely variable between difference devices, age, temperature etc).

    Having run this experiment I'm inclined to think that you're not likely to have a significant problem running the BoB with the inputs connected to a 24V-driven NPN sensor. If might be that, over time, the opto-couplers degrade, but I'm not convinced that this would result in failure. If it does, the optos are easily replaced (or the BoB, if these are still available after the failure).

    BUT, I have decided that I'll be powering the BoB and the sensors with a common 12V supply - it's a personal choice but I will keep the reverse bias voltage to less than the maximum expressed on the datasheet.

  5. The Following 2 Users Say Thank You to Doddy For This Useful Post:


  6. #165
    Quote Originally Posted by Doddy View Post
    Okay, a nice Sunday experiment.

    With reference to https://www.renesas.com/en-eu/produc...tandard-p.html - which discusses the effect of reverse-biasing an opto-coupler (section 1.5).

    I've hooked up a brand-new 4n25 opto-coupler, 1K between anode and +10V, cathode connected to either 0V (opto = on) or through a 10k resistor to 24V (opto = off, reverse biased, simulating the sensor behaviour). Collector to +10V, emitter through a 1k to ground. DVM across emitter and ground.

    With the cathode connected to 0V (on), the voltage at the emitter raises from 0.0 to 9.06V.

    Now, I connect the cathode to the 24V supply via the 10k resistor (simulating the sensor internal pull-up of 10k). Predictably, the emitter voltage drops to 0V as the opto-coupler turns off.

    So, the real test - leave like that for 5 minutes, then disconnect the 24V supply and ground the cathode.

    Result - emitter voltage rises to 9.06V

    Conclusion - for a short-duration (5 minute) exposure to 24V (and a reverse bias of 14V) the performance of the opto isolator is not changed.

    However, measuring the voltage across the 10k gives 0V (i.e. no voltage drop - no current flow) - the voltage hasn't reached the avalanche voltage of the opto's LED.

    Since then, I've added in a second PSU giving me a range upto 60V, in place of the 24V supply. Cranking the voltage up it was evident that the avalanche region of the LED in the opto was around 50V. Removing the 50V showed an emitter voltage of 9.01V (a 0.05V reduction from previous). Replacing the 10K resistor with a 2.2k resistor (to increase the current flow during the reverse-biasing), and the emitter voltage dropped to 8.84V (further degeneration). Note, this effect does appear to be permanent, but not increasing (in the 5-10 minutes I waited).

    So, what do I think? Reading random articles on the internet does suggest that reverse-biasing the LED will result in a deterioration of performance over a period of years. The article above suggests that even short duration reverse biasing can result in deterioration.

    However, the avalanche voltage may be substantially higher than the datasheet (clearly you can expect the opto-isolator to tolerate a 6V reverse bias without damage - but the actual headroom that you have between that and the actual avalanche voltage is unknown, and likely variable between difference devices, age, temperature etc).

    Having run this experiment I'm inclined to think that you're not likely to have a significant problem running the BoB with the inputs connected to a 24V-driven NPN sensor. If might be that, over time, the opto-couplers degrade, but I'm not convinced that this would result in failure. If it does, the optos are easily replaced (or the BoB, if these are still available after the failure).

    BUT, I have decided that I'll be powering the BoB and the sensors with a common 12V supply - it's a personal choice but I will keep the reverse bias voltage to less than the maximum expressed on the datasheet.
    Ok ,thoroughly does not even closely describe your commitment in helping me out.
    Thank you for that.

    Ok so...i decided to do the following based on this thread and other threads.

    Since there seems to be 9.4k ish in line in the proximity switch emitter, i put a 4.7k resisitor in series connected to ground.

    When connected to a 24vdc psu, this will give me about 8 volts at the point of connection at the bob. in the "open "position.

    When in the " closed " position the emitter goes to 0v.. hope this will work.


    I will report back when all is operational.

    Doddy thanks again for doing research on this subject.


    Grtz. Bert




    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  7. #166
    Quote Originally Posted by driftspin View Post
    Ok ,thoroughly does not even closely describe your commitment in helping me out.
    Thank you for that.

    Ok so...i decided to do the following based on this thread and other threads.

    Since there seems to be 9.4k ish in line in the proximity switch emitter, i put a 4.7k resisitor in series connected to ground.

    When connected to a 24vdc psu, this will give me about 8 volts at the point of connection at the bob. in the "open "position.

    When in the " closed " position the emitter goes to 0v.. hope this will work.


    I will report back when all is operational.

    Doddy thanks again for doing research on this subject.


    Grtz. Bert




    Verstuurd vanaf mijn SM-A320FL met Tapatalk
    In honesty, I'm doing this for me, as much as anything - I will need to start thinking of wiring pretty soon, and you're bringing up the questions that I need to answer for myself.

    I think the NPN sensors the black wire is actually the collector, not emitter (I guess the emitter is connected to blue/0v)

    Re your proposal. Think carefully of what you're trying to achieve. With the NPN providing a switch to ground (current sink), by placing a resistor from the output to ground will give you a low(ish) resistance to ground even when the NPN transistor is OFF - the LED will still illuminate (you'll get around 1.5mA through it - enough to illuminate it, probably enough for the current through the opto's transistor to actuate the input to the UCx00 - the input impedance of that is something like 50k to ground (and 4k7 to +5).

    Try it, by all means, but don't be surprised if the input is permanently on.

    The easiest solution is to simply tack a small signal diode (1n4148 is probably the most common) across the pin 1/2 of each opto - in the opposite sense to the opto's LED (i.e. cathode to pin 1, anode to pin 2). That way you cannot reverse bias either diode beyond the forward conduction voltage of the opposing diode - max of 0.6V by the 1n4148 across the opto's LED, or around 1.5V by the opto's LED across the 1n4148. Essentially, this will limit the voltage at the input to the BoB to the V-Ref provided by the BoB's onboard regulator (~10V) plus 0.6V.

    Of course, this (and the idea that you proposed) both serve to reduce the switching voltage to something around 10V, which is why I still think that just using a 12V supply to the BoB and to the sensor is an easy alternative.

  8. #167
    Quote Originally Posted by Doddy View Post

    Try it, by all means, but don't be surprised if the input is permanently on.

    .
    Ok i get it.

    So best would.be to raise voltage just over 9.3 or what ever comes out the bob with nothing connected.

    I really like your idea of the reversed diode.

    This will act as an indicator for status at the same time.


    Grtz Bert.

    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  9. #168
    Hey guys,

    I need some advice on how you guys connected the 8 stepper wires to the 4 wire shielded cable.

    Did you guys just solder and heatshrink it to the cable?


    I also feel like i need to connect the cable shield to the body of the stepper motor.

    Some photos would do the trick :-)


    Any advice is welcome.


    Grtz Bert.

    Verstuurd vanaf mijn SM-A320FL met Tapatalk
    Last edited by driftspin; 13-06-2018 at 10:53 PM.

  10. #169
    HI guys,

    for a 2.2 kw spindle.
    What size bit can i use to level my wooden bed surface?


    Grtz Bert

    Verstuurd vanaf mijn SM-A320FL met Tapatalk

  11. #170
    Quote Originally Posted by driftspin View Post
    Hey guys,

    I need some advice on how you guys connected the 8 stepper wires to the 4 wire shielded cable.

    Did you guys just solder and heatshrink it to the cable?


    I also feel like i need to connect the cable shield to the body of the stepper motor.

    Some photos would do the trick :-)


    Any advice is welcome.


    Grtz Bert.

    Verstuurd vanaf mijn SM-A320FL met Tapatalk
    I just soldered with heatshrink. Not pretty but it works :D

    My stepper motors are grounded through the machine frame.
    If connecting the wire shield aswell it might create a loop?

    Skickat från min SM-G955F via Tapatalk

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