Inductive Limit Switch problem

[Kitwn]

Just been perusing the HDBB2 breakout board from CNC Drive. This appears to be nothing more than an up-market version of the cheap Chinese parallel port breakout board with opto-coupled inputs and a number of improved features. The company advertise this board as suitable for use with LinuxCNC direct from an old PC's parallel port as well as with CNC Drive's own products. Since this board is a necessary add-on to the UC400ETH Ethernet controller anyway, it might make a good starting buy for a budget build with the option to upgrade at a later date.
Has anybody used one of these in this way?

https://www.benl.ebay.be/itm/HDBB2-b...-/121287188690

[dazp1976]

And do you think you'll need more than 10 inputs and 24 outputs.? I'm also not sure if some of those Outputs on the second port can be configured as inputs in software.? Only if you plan on having an ATC will you probably need more than 10 inputs.

Regards the Cheap BOB then yes, of course, it will make a difference. It's like having 500HP engine and fitting bald tyres.? Pointless.!

Any machines only as good as the weakest link so fitting a good card with a cheap BOB that probably can't keep up doesn't make sense to me. This whole thread proves this.
I fit good electronics, which yes cost more, but I never have any of this shit to deal with and the extra cost is made back by the fact I'm not running around fixing machines or put another way the owner doesn't have any downtime which costs money.!! . . . . You get what you pay for.!

If your going to use a cheap BOB then save your money don't buy ESS or ETH400 and use Linux CNC. You have half a chance of good machine and won't cost anything other than it's a steep learning curve.

Looks like I can get it ok so I'm leaning towards the UC300eth-5lpt and opting for a UCSB breakout board. Get some cables and NPN-NO sensors too and use it for axis, limit & stop control- http://cncdrive.com/UCSB.html.
Then I'll use my cheap board for spindle control and any relays.
What do you reckon?
Futureproofs it in case I ever get to build a 3 axis ATC or similar at a later date. (likely £3000 ish with tooling....ouch!!!! Don't tell the wife!)

I'd be comfortable with the ESS but like you say. It gives me the option of going away from Mach3.
It's a tricky decision.

[Doddy]

That UCSB board, on paper, looks to be a pretty good BoB for the extra ports on (at least) the UC300ETH. It's pricey, though, but looks to be built like the proverbial brick-outhouse. Probably a bit of an overkill for most machines (how many layers of optical isolation do you really need?) but if you're happy with the price. I'd be thinking that if I was ever to need more than the 12 outputs (bearing in mind you'll need 8-9 for a 4-axis) then I'd relegate the axis stepper signals to a cheaper BoB on the port 2/3 on the 300 and retain the highly flexible I/O of the UCSB for other purposes on the machine.

[Kitwn]

At last!! A nice man in a white van turned up today with a box from RS containing the cable for re-wiring my new proximity sensors. I managed to get the old wiring ripped out of the drag chains and the new cables in place for the Y and Z sensors before wine 'o' clock.

Tomorrow I should have time to get the two X axis sensors wiring in place and all the soldering done to connect everything up to the control box. Sadly the two remaining miniature relays for coupling the sensors into the BOB are a separate order which is still on it's way from somewhere on planet Earth, but I should be able to test all the wiring and confirm that everything else works as expected. I already have a list of outstanding projects from Mrs W-N that are waiting for the machine to be back in action so I'm hoping the relays arrive soon!

[Kitwn]

I was just getting to the end of all the new wiring when the same nice man in the same white van turned up with another parcel from RS containing the relays. Apart from a slight problem mentioned elsewhere I now have the 4 new proximity sensors wired up with screened cables back to the controller and the relay/transistor interface into the BOB finished and tested.
Tomorrow I will tidy up the impressive mess and get everything put back together and ready for testing and alignment. Auto-squaring will need to be re-calibrated and the finished aluminium (rather than the old plywood prototype) Z axis lined up as well. Might be able to make something soon!

[cropwell]

Kit,

If you find reed relays in the homing circuit don't give you a consistent zero point, you could try DC-DC SSR's

[Kitwn]

Kit,

If you find reed relays in the homing circuit don't give you a consistent zero point, you could try DC-DC SSR's

To be honest I'm hoping I don't have to try anything else for quite a while. I've spent too much time messing about with the machine rather than making anything with it. I'm reasonably confident that the relays will work OK. The response time (including bounce) is specified at 0.5mS. Variation in response time is going to be a lot less than that, especially as they are safe in the control box and not being vibrated and bashed about like the old microswitches were. If the dimensional errors from all the other weaknesses in this machine prove to be small enough for the relays to become significant I shall be very happy!

[Kitwn]

Well I never thought we'd end up with 8 pages of guff on this over three weeks, with an assortment of new/abandoned circuit designs and quite so much head-scratching!

Anyway the machine is now back together and appears to be working every bit as well as it did before I decided to replace the microswitches with inductive proximity sensors. The real excitement is that I can now see how well the all-aluminium Z axis behaves compared to the old plywood prototype I've been using for the last year or more.

[dazp1976]

Well I never thought we'd end up with 8 pages of guff on this over three weeks, with an assortment of new/abandoned circuit designs and quite so much head-scratching!.

Lockdown sending us all a bit loopy that is

Just bought a load of prox sensors myself. Might get round to fitting them in the next year maybe.
Have fun with yer machine and hope it behaves for you.

[Kitwn]

Lockdown sending us all a bit loopy that is

Just bought a load of prox sensors myself. Might get round to fitting them in the next year maybe.
Have fun with yer machine and hope it behaves for you.

Actually the lockdown isn't making too much difference in the W-N household. Except that now we have to call it "Social Distancing" instead of "Anti-Social Distancing".
Thanks for the good wishes, I'm looking forward to getting on with the list of projects I have outstanding. Funny how everything else seems to rely on the CNC machine as soon as you have one.

Kit