Magnetic Encoder Maximum Cable Length

[samlogan87]

Hey Everyone,

What’s the maximum recommended length for the ribbon cable?

Cheers
Sam

[dc42]

@samlogan87 I think 2m shouldn't be a problem provided you don't run it next to unshielded stepper motor cables.

[samlogan87]

@dc42 awesome thank you. Are they any better than the quadrature encoders I currently have. I believe they are 2000cpr

[dc42]

@samlogan87 I'm sorry, I misread your post, I thought you were asking about the magnetic filament monitor. If you are referring to the ribbon cable between the magnetic shaft encoder and the Expansion 1HCL board, that cable carries a 5MHz SPI signal. We're recommending a maximum 150mm cable length, although I suspect that 250mm would work.

The resolution of the magnetic encoder is 16384 counts per rev. A 2000 ppr encoder provides 8000 counts per rev although the counts in each group of 4 will not be completely uniform. Your 2000 cpr encoder might actually be 2000 ppr or it might be 500 ppr.

[samlogan87]

@dc42 ah bugger. That might be a pain. If I was to use shielded ribbon cable would that work? I see you can buy it, which I never knew about

[dc42]

@samlogan87 I doubt that shielding the ribbon cable would help much. It's the capacitance of the cable that limits the transfer rate.

Many years ago I used a special ribbon cable that had ground wires interleaved between the standard conductors. It's possible that a cable like this would allow increased length, if such cables are still available.

What's the reason for wanting a large distance between the stepper motor and the 1HCL board?

[samlogan87]

@dc42 ah bugger. It’s just where I currently have the two boards mounted is inside an electrical part off the side of the printer meaning they would need to be about 650-700mm long. I guess I could move the boards. Just a bit worried about heat as I will be heating the chamber at some stage