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.