(1) Just a quick reply to cheap and small stepping motors. You might like to look into "28Byj48". See Ref 3 of the Reference below.

28Byj48 Reference below.

BTW, you might like to skim this post:

I am also thinking of making a java hole robot.

nanowerk.com/news2/space/newsid=57620.php

Now I am testing my Pico MicroPython Program controlling 4 I2C PCF8574 8-bit IOx modules each of which moves 2 tmc2160 stepper motor controller each moving 1 stepper motor.

The 4WDs in the background are using BLDC and geared DC motors (TT130 and N20s). The tmc2160 can be configured and diagnosed using SPI (I am testing at the same time tmc2190 with UART interface). A full listing of the pico code is shown in the Penzu diary below.

tmc2160_test52_2022叛0501 - penzu.com/p/2a05a9cf

The moon's java tube can be 500 metres wide. So we need to modify our designs for the moon. :)

Motor Coil Current Measurement Notes - Introduction

Now I am making a plan to measure motor current, which is what the OP is asking for. I am doing it in two steps: (1) Using a resistor, perhaps 0.5 ohm, in series with the motor coil to ground. I can use a scope to display the current waveform. (2) use a current mirror/amplification chip to do the job.

The current mirror chip I will be using is the following:

And the current mirror/amplification spec:

And my current measurement hardware setup:

Because using the current mirror chip, I need first use a stupidly looking 0.5R resistor and a scope to help getting a rough picture of the motor current waveform.

Ah, locking down supper break. See you later.