1HCL measure encoder PPR in open loop.

[CNCModeller]

Hi All,
Is there any way to demand a number of full revolutions of a stepper motor in open loop and measure the number of encoder pulses with a 1HCL.

I'm trying to use an encoder from a CNC lathe rotary axis to feedback position on a polar printer rotary bed but I don't have any useful documentation on the ppr for the encoder and magnetic ring pair.

My bed has a 36 to 1 ratio between the stepper motor and bed rotation so the hope is to open loop drive the motor 36 turns and measure the number of pulses for a single revolution of the magnetic encoder ring.

Any constructive thoughts would be much appreciated.

Many thanks in advance.
Barry M

[dc42]

@CNCModeller to use a EXP1HCL with feedback from the bed position, you need to use two encoders: one to measure the motor shaft position (which we need to ensure correct commutation) as well as the one to measure bed position. See https://docs.duet3d.com/Duet3D_hardware/Duet_3_family/Duet_3_Expansion_1HCL#linear-quadrature-encoder-plus-magnetic-shaft-encoder. Although that talks about a linear quadrature encoder, the setup using a rotary quadrature encoder on the bed would be the same. So you will need to use one of our magnetic encoder boards attached to the back of the motor, assuming that the back of the shaft is accessible so that you can attach a magnet.

A slight complication is that the EXP1HCL firmware may need to be updated to support a continuously-rotating axis

[CNCModeller]

@dc42 Ahh, sounds like things have moved on a fair bit since I last was looking into this. That sounds great. I'll order a magnetic encoder board, it'd be good if you can confirm the bit about the 1HCL firmware for the bed axis.

I also have optical linear quadrature encoders in hand for my mill conversion so I assume I'll need the motor commutation magnetic encoder board with the 1HCLs for those too.

Thanks for the heads up!

All the best
Barry M

[CNCModeller]

@dc42 could you please point me in the direction of where to get a magnetic encoder board? Can't see one listed in the shop or at e3d.

Many thanks
Barry M

[dc42]

@CNCModeller the magnetic encoder board isn't listed yet because the first production batch is currently being manufactured. We'll announce it when they are available.

[CNCModeller]

@dc42 ah ok. Please can you put my name down for one when they arrive.

Many thanks
Barry M

[CNCModeller]

Hi @T3P3Tony is there any news on the availability of the magnetic encoder boards?

Many thanks
Barry M

[T3P3Tony]

@CNCModeller we have them, just working on the documentation and then will get them out to our resellers #soon