MK1 Steel router build log 1500x800x200

[Doddy]

Doddy thank you for your explanation.

Please verify if i understand you correctly and false or true the below.

Firstly, you're asking questions on a BoB who's design is somewhat unknown to me, If you have a URL to the actual user manual for the BoB that will help an awful lot in removing uncertainty, however, many of these are supplied without such detail. In the absence of this design data here's my logic behind the conversation to-date:-

Examining the content of the BoB's component layer - there is no evidence of additional components mounted on the opposite side (e.g. through-hole pins), which leads me to suspect that, the usually obvious, opto-isolators, are not included as part of this design. There looks to be three logic devices - pin-counts support the usual combination - 2x 74xx245 octal driver devices (of whichever technology family - HC, HCT, LS, etc). These are almost always driven from a 5V supply (which is compatible with the UC300eth and parallel ports in the PC). You would need these 2 devices to give the 5V buffering for the 2x5 (=10) motor drives, presumably the 11th being the common enable to the stepper drivers, another for the spindle relay - in fact, this is supported by the silk-screening on the board - 12 outputs. The smaller 14-pin device I would guess at something like a 74xx13 device - a hex Schmitt-trigger inverter device, which would support upto 6 inputs - 4 we know already for the IN1-4 inputs. My guess is the remaining 2 gates unconnected. The choice of a 74xx13 would be intelligent (as well as common) as these afford some noise immunity on the incoming signals.

What's left on the board that's visible?, an SMD transistor that will be used to switch the relay, a PTH diode (1N4148?) for back-emf protection on the relay coil, a couple of LEDs - I guess power, and spindle on/off, discrete resistors for the LEDs and the base-drive for the transistor; some SIL resistor packages for pull-up, or pull-down (can't tell) on the inputs to the board, and a smattering of decoupling capacitors. That's pretty much it.

No on-board regulation and a requirement to source the 5V supply from the USB connector.

No charge-pump for the PWM drive, or op-amp (typically LM358s in these basic designs), no provision for anything other than the USB supply.

1 -
Pulse, dir, enable, from uc to 5 axis bob is 5 volt level. based on 5volt supply circuit to bob/uc.

TRUE.

2-
External psu connection 12/24vdc to bob is for 0-10volt /pwm only.

FALSE - as above - no evidence in the image linked to the you-tube video of anything other than the USB power-input for the 5V supply.

Other BoBs, such as the one I have in front of me, have a separate 12-24VDC supply to provide the isolated 0-10V drive output to the spindle drive, but there's no evidence of any such circuitry on the BoB linked.

3-
Estop / axis end switches.
I have 24vdc volt power supply which will be used to power the e-stop circuit / relais.


1 free contact on e-stop relais will connect to bob e-stop pin / bob gnd.

That will work, provided you have a common ground reference for both the logic supply to the BoB and the 24V supply. <-- ignore that last bit - that's wrong

A switched ground, provided the BoB has on-board pull-up (which I'm pretty certain it will) is a safe mode of connecting to the system. Do not, however, try any 24V signalling into this BoB.

4-
Homing.

LJ8A3-2-Z/BX
These proximity switches are NPN.


Now because they run off a higher voltage separate psu i have to connect 5 volt ground to 24volt ground or they will not work icm with 5axis bob inputs.


This worries me a little since i thought the bob would be 24v on the inputs for homing
based on the applied external psu.

I have read on this forum 24v signals are preferred for interference reasons.

Okay, so, do the proximity switches have internal pull-up resistors to their supply? (put a DVM on resistance scale between +V and the output - if there is a relatively low impedance - say <50k, between the +V and the output, and this is the same regardless of whether you use the meter red/black leads between the +V and output) - then this is a strong indication that there is an internal pull-up. In this case, connecting the output from the proximity switch to the input of the BoB is likely to damage the BoB. It's uncertain to me whether this would risk further damage to the UC300eth - I'd not recommend trying.

If there's no low resistance between output and +V on the proximity switches then I'd guess there's no pull-up, in which case you *could* pull-up to the BoB's 5V supply, but you lose the benefit of the noise-immunity offered by the wider supply range. Not recommended.

5-
I read your warning about the opto isolation, this worries me to.

Having a € 175,- motion controller i.c.m. with a € 5,- bob that does not protect the controller... does not make sense.

Please comment on the above.

Yup. I'd look at a <$5 BoB that includes Opto couplers, to be honest.



Edit:

This is the board that I have, and referenced above:

https://www.ebay.co.uk/itm/183048728446.

I don't necessarily recommend this one, but you can immediately recognise other component blocks - the 5 opto-isolators running down the left edge for inputs. A similar one mid/lower board that provides isolation from the PWM input into the charge-pump/integrator op-amp set-up with the tiny 8-pin SMD chip in the lower-right corner (together with a chunky capacitor or two as part of that circuit). Just below the relay - a SMD regulator likely for the op-amp. So, opto-isolated inputs, a 0-10V drive for spindle speed that is isolated from the logic supply, and the separate 12-24V supply for this op-amp. None of that visible on the board that you linked.

Edit 2:

Your board can be made to work - but you have to be aware of it's design and any limitations.

[Doddy]

Your board can be made to work - but you have to be aware of it's design and any limitations.

I'd also consider when to cut your losses if you want to continue with your original design aims.

[driftspin]

I'd also consider when to cut your losses if you want to continue with your original design aims.

Ok doddy,


I think i am lucky, this is what i recieved.



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[Doddy]

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.

[driftspin]

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.

[Doddy]

So there is some type of voltage regulator on the inputs circuit.

Agreed - our results tally.

http://www.everlight.com/file/ProductFile/EL817.pdf

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.

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".

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.

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.

[Doddy]

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.

[driftspin]

Firstly, you're asking questions on a BoB who's design is somewhat unknown to me, If you have a URL to the actual user manual for the BoB that will help an awful lot in removing uncertainty, however, many of these are supplied without such detail. In the absence of this design data here's my logic behind the conversation to-date:-

Examining the content of the BoB's component layer - there is no evidence of additional components mounted on the opposite side (e.g. through-hole pins), which leads me to suspect that, the usually obvious, opto-isolators, are not included as part of this design. There looks to be three logic devices - pin-counts support the usual combination - 2x 74xx245 octal driver devices (of whichever technology family - HC, HCT, LS, etc). These are almost always driven from a 5V supply (which is compatible with the UC300eth and parallel ports in the PC). You would need these 2 devices to give the 5V buffering for the 2x5 (=10) motor drives, presumably the 11th being the common enable to the stepper drivers, another for the spindle relay - in fact, this is supported by the silk-screening on the board - 12 outputs. The smaller 14-pin device I would guess at something like a 74xx13 device - a hex Schmitt-trigger inverter device, which would support upto 6 inputs - 4 we know already for the IN1-4 inputs. My guess is the remaining 2 gates unconnected. The choice of a 74xx13 would be intelligent (as well as common) as these afford some noise immunity on the incoming signals.

What's left on the board that's visible?, an SMD transistor that will be used to switch the relay, a PTH diode (1N4148?) for back-emf protection on the relay coil, a couple of LEDs - I guess power, and spindle on/off, discrete resistors for the LEDs and the base-drive for the transistor; some SIL resistor packages for pull-up, or pull-down (can't tell) on the inputs to the board, and a smattering of decoupling capacitors. That's pretty much it.

No on-board regulation and a requirement to source the 5V supply from the USB connector.

No charge-pump for the PWM drive, or op-amp (typically LM358s in these basic designs), no provision for anything other than the USB supply.



TRUE.




FALSE - as above - no evidence in the image linked to the you-tube video of anything other than the USB power-input for the 5V supply.

Other BoBs, such as the one I have in front of me, have a separate 12-24VDC supply to provide the isolated 0-10V drive output to the spindle drive, but there's no evidence of any such circuitry on the BoB linked.



That will work, provided you have a common ground reference for both the logic supply to the BoB and the 24V supply. <-- ignore that last bit - that's wrong

A switched ground, provided the BoB has on-board pull-up (which I'm pretty certain it will) is a safe mode of connecting to the system. Do not, however, try any 24V signalling into this BoB.



Okay, so, do the proximity switches have internal pull-up resistors to their supply? (put a DVM on resistance scale between +V and the output - if there is a relatively low impedance - say <50k, between the +V and the output, and this is the same regardless of whether you use the meter red/black leads between the +V and output) - then this is a strong indication that there is an internal pull-up. In this case, connecting the output from the proximity switch to the input of the BoB is likely to damage the BoB. It's uncertain to me whether this would risk further damage to the UC300eth - I'd not recommend trying.

If there's no low resistance between output and +V on the proximity switches then I'd guess there's no pull-up, in which case you *could* pull-up to the BoB's 5V supply, but you lose the benefit of the noise-immunity offered by the wider supply range. Not recommended.




Yup. I'd look at a <$5 BoB that includes Opto couplers, to be honest.



Edit:

This is the board that I have, and referenced above:

https://www.ebay.co.uk/itm/183048728446.

I don't necessarily recommend this one, but you can immediately recognise other component blocks - the 5 opto-isolators running down the left edge for inputs. A similar one mid/lower board that provides isolation from the PWM input into the charge-pump/integrator op-amp set-up with the tiny 8-pin SMD chip in the lower-right corner (together with a chunky capacitor or two as part of that circuit). Just below the relay - a SMD regulator likely for the op-amp. So, opto-isolated inputs, a 0-10V drive for spindle speed that is isolated from the logic supply, and the separate 12-24V supply for this op-amp. None of that visible on the board that you linked.

Edit 2:

Your board can be made to work - but you have to be aware of it's design and any limitations.

Ok thank you for breaking down the 5 axis bob so detailed.

I have not recieved the bob yet.


I will post a picture when i do.



This limits my options for wiring for now.



Grtz. Bert

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