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I have read somewhere that one can get higher accuracy for threading with dual encoders and, of cource a 1 PPR homing pulse. I would run one disc, with 2 sensors, perhaps LEDs to make sure they are out of phase.
I have to admit the cost is looking a bit daunting! If I read the specs correctly, the Pico can drive 4 motors (with amps), take 4 encoders for the steppers 16 inputs and 8 outputs? Can I use some digital inputs for the spindle encoder, or is it better to use 2 axis encoder inputs?
I am happy to have various cards, or one card, depending on flexibility and cost.
Regards
Peet

Yes, a normal encoder has two signals that are out of phase with each other and an index pulse once per revolution. A differential encoder is what is usually used and they have 6 signal lines A, A~, B, B~, Z, Z~ with Z being the index line. Thread quality will depend on the whole package not just the encoder.

John

Soundreflections wrote:In that case then you just need one set of encoder inputs. All LinuxCNC "encoder" modules have three inputs, Phase A, Phase B and the Index.
If your disc has about 100 slots then you can use a parallel port for all IO.
if you go up to 1000 slots then you need a dedicated IO board such as the Pico or Mesa. Now that we know you are only talking about one encoder, the 7i76 looks like a good choice again.

My lathe has 100 slots, threading works nicely.

if you want to get started for minimal outlay one of the very cheap eBay kits might suit: (comes with a spare motor)
www.ebay.co.uk/itm/3-Axis-TB6560-Driver-...NC-Kit-/251095203360
Or, slightly higher quality and more modular and only 2 axis
www.ebay.co.uk/itm/Cnc-2-Axis-Lathe-Cont...3-EMC2-/320946904472
That second set is a lot like the drivers I am using, except better and higher current. I don't think you would go far wrong with that.

Hi,
Thanks for the replies. I have now got a pulley for my motor and I have today bought a belt that actually fits the new setup. I need to gte down to programming my VFD to actually give me some torque where I need it, as I currently not start my lathe in its highest gearing.

Andy, you are tempting me sorely with your findings. I am especially looking at the second finding you posted, as it has stronger motors than the first and is still cheaper than what I think I can buy the various parts for. I cannot tell whether it includes a spindle encoder interface or not, I certainly do not think it would include motor encoder interfaces, but I am sure I can add those at a later stage if I want to maintain manual with DRO.
I take it you are quite sure I will get this setup running on Linux CNC?

Thanks and regards
Peet

I have now spent the day cleaning my entire moving assembly (temporarily gone blank for the term), every gear, thread... Now I finally have a very smooth working lathe, I cleaned the grease I had before put on the ways off, using only machine oil as a lubricant. I realise I have used grease on all the other slides, which I realise is probably not the best, which is why I was advised against it (belatedly) at projectsinmetal, where I first started posting about my lathe.
Now of course I cannot think of something to make!
Regards
Peet

Way Oil is the proper lubricant for machine ways. I use Mobil Vactra Oil #2 Way Oil for all my machine ways.

You could make me some oil cups for my Samson lathe LOL.

John