XR-1000 Pico-Based Robotic Motion Subsystem

RE: XR-1000 Pico-Based Robotic Motion Subsystem

beacon_dave — Sun, 03 Apr 2022 20:44:00 GMT

Compact edition...

Using all Lego parts. The yellow 1x1x2 bricks are likely going to try and move, so some glue may be required.

Same from the rear. Using the 'bow' for cable exit.

Compact edition number two... Gearbox flange is recessed again for a more flush finish.

Using a 3D printed front. Going to have to unscrew the gearbox cover to assemble or you cut the 3D print in half. The bottom corners are glued to smooth 1x1 tiles and the top corners are glued to 1x1 plates with studs on top to allow a good snap fit to the base plate.

From the rear, using the 'bow' again for cable exit.

The 3D print will require pockets to clear the centre studs on the lower base plate. The outside edges glue to the 1x1 smooth tiles.

RE: XR-1000 Pico-Based Robotic Motion Subsystem

beacon_dave — Sun, 03 Apr 2022 15:51:41 GMT

Modified design avoiding the need for any 3D printing. Overall it is still three standard Lego bricks high and the gearbox output shaft is still in a central position.

Gearbox flange moved forward and a 1x4x2 'arch' now used for the front face. A smooth tile is used below the gearbox as there is not enough clearance to accommodate the studs on a standard plate. Translucent 1x2x2 wall element used on the side to allow clearance for motor PCB internally.

View from rear, similar to before but arch at the front instead of 3D printed part. Slot for cable exit visible on rear.

Another view from the rear but this time using a 1x4x1 'bow' to provide a cable exit.

RE: XR-1000 Pico-Based Robotic Motion Subsystem

beacon_dave — Wed, 30 Mar 2022 17:34:09 GMT

Design modified to accommodate the PCB on the side of the motor. Replacing the two Lego Technic bricks with a 3D printed brick with a channel cut out of it.

It is glued to a 1x2 flat tile which then snaps onto the 4x4 base plate. The circles show where the Technic holes would have been.

A 1x1 plate is now used at the rear leaving a slot for the cable exit. It could be a 1x2 plate as the cable doesn't need much room.

Front view showing the PCB + glue (dark green) accommodated within the channel of the 3D printed side brick. This is symmetrical so can be be on the left or on the right as preferred.

Top view showing the space at the back available to get the cable from the PCB to the slot at the rear. May need a dab of glue to keep it away from the motor axle protruding to the rear.

RE: XR-1000 Pico-Based Robotic Motion Subsystem

beacon_dave — Tue, 29 Mar 2022 15:14:38 GMT

Ok, how about this ?

complete with a slot at the rear for cable exit...

The smooth tile at the lower front is there to make 3D printing easier and hopefully helps avoid injury by not having to cut studs off.

The gap at the front can be filled with a simple 3D print or laser cut-out and the motor flange screwed into it.

The Technic brick holes should help provide some cooling for the hard-working little motor.

The gearbox flange can be rotated if needed to suit the PCB on the moto at the rear.

And now for the hard part, what colour should it be ?

RE: XR-1000 Pico-Based Robotic Motion Subsystem

beacon_dave — Tue, 29 Mar 2022 10:17:45 GMT

Here is is a version using a Techinc beam in the side as previously discussed. Single beam in a 'geometrically correct' position.

And again but with two Technic beams. More holes but they are offset by one plate vertically.

RE: XR-1000 Pico-Based Robotic Motion Subsystem

beacon_dave — Mon, 28 Mar 2022 13:20:17 GMT

Hi Shabaz,

Can you confirm a couple of dimensions for me ?

The length of the white gearbox cover from the front face of the flange to where it joins the motor.
(motor + gearbox is 21mm overall but not clear of where the spilt is).

The PCB in your annotation looks like it is 8.5 x 7mm and is offset from the gearbox join by 3mm ?
PCB looks less square in the photo, but I guess they may vary in production and glue blobs always make life interesting when measuring.

Finally the dimensions of the motor bearing and the shaft that protrudes from it. Plenty of room with the current 4x4 brick unit design but things start to get a very tight in this area if aiming for a smaller 3x3 brick unit design.

It looks like the white gearbox flange and cover can come off (two screws on the front flange) allowing for the gearbox to be passed through a 15mm dia hole from behind and then the cover put back on from the other side. Is that correct ?

RE: XR-1000 Pico-Based Robotic Motion Subsystem

shabaz — Tue, 08 Mar 2022 00:00:20 GMT

In case anyone else hits such an issue when printing text to USB using the Pico C/C++ SDK..

If I modify this file in the Pi Pico SDK:

/pico-sdk/src/rp2_common/pico_stdio_usb/include/tusb_config.h

and change the line

#define CFG_TUD_CDC_TX_BUFSIZE  (256)

to:

#define CFG_TUD_CDC_TX_BUFSIZE  (1024)

and then build the project as described earlier, then I can print more, which sorts out the help menu, it is fully printed:

However, this isn't a great fix, there must be a better way to do this surely. I'll raise it as an issue on the GitHub repo site.

RE: XR-1000 Pico-Based Robotic Motion Subsystem

fmilburn — Mon, 07 Mar 2022 00:39:24 GMT

Hi Shabaz,

This is nicely done with excellent documentation. The use of modules makes good sense for ease of construction and availability. It looks like it would be well suited to teaching robotics. Do you have a use in mnd?