Building the MeArm Pi (Pi Zero)

This document is relevant only for the following hardware:

  • mearm-pi

Tips for success:

Before you start

This version of the instructions is for a Raspberry Pi Zero. If you are building your MeArm Pi using a model B+ style Raspberry Pi then please use these instructions. You can also view these instructions as a pdf.

Before you build the arm you should get your Raspberry Pi SD card ready so you can get it in more easily. Download the latest image from here and follow these instructions to flash it.

Once you’ve done this you’re ready to start building your MeArm Pi. Click “Start” to get going - if you need to repeat a step you can press the “repeat” button or press “loop” to keep looping a step until you’re ready to move on to the next.

Steps

  • #1 Fit the servo into the Base PCB
  • #2 Fit the centre piece over the servo
  • #3 Keep the cable tidy
  • #4 Add the base ends
  • #5 Add the left side
  • #6 Add the right side
  • #7 Add the elastic band
  • #8 Slot the crossbrace into the left main strut
  • #9 Attach the long strut
  • #10 Attach the left rear strut
  • #11 Attach the lower lever
  • #12 Attach the right main strut
  • #13 Attach the lower right upper strut
  • #14 Attach the upper strut
  • #15 Attach the right rear strut
  • #16 Screw the arm on to the base
  • #17 Screw the rear strut to the base
  • #18 Insert the right servo
  • #19 Clip the right servo on
  • #20 Wind the cable
  • #21 Insert the left servo
  • #22 Clip the left servo on
  • #23 Wind the cable
  • #24 Attach the elastic band
  • #25 Slot the left grip side on
  • #26 Slot the centre grip support on
  • #27 Slot the grip front plate on
  • #28 Slot the left grip side on
  • #29 Slot the rear grip support on
  • #30 Place the left grip over the servo
  • #31 Put the right grip in place
  • #32 Slide on the grip base
  • #33 Attach the grip to the arm
  • #34 Tidy the cable
  • #35 Align the two base pieces
  • #36 Attach the HAT to the Pi
  • #37 Insert the spacers and screws
  • #38 Screw down the Pi
  • #39 Insert the front and back sides
  • #40 Insert the short sides
  • #41 Attach the base cover
  • #42 Attach the joystick caps
  • #43 Slide the arm on to the base
  • #44 Attach the front elastic band
  • #45 Attach the main cable

#1 Fit the servo into the Base PCB

Take the base PCB and place it face up (look for the word TOP to help) then insert the servo that has a double ended arm (there's only one of these) into the hole in the centre. It needs to go the right way around so align the servo arm with the circle on the board

#2 Fit the centre piece over the servo

Find the centre piece (part #1) and slide it down over the servo. The tabs are sized so it will only go on one way so if it doesn't go on easily, try it the other way around

#3 Keep the cable tidy

Wind the servo cable around the centre piece to keep it tidy. Looking from above it should be wound in a clockwise direction through the two holes on each side of the servo

#4 Add the base ends

Slide the end pieces (parts #2) down over the centre piece so that they slot into the base. Again, these will only go on one way around

#5 Add the left side

Slide the left side (part #3) over the pins in the base

#6 Add the right side

Slide the right side (part #4) over the pins in the base

#7 Add the elastic band

Take one of the elastic bands and loop it around the base so that it sits in the upper set of slots in the side pieces. You can put this assembly to one side for now

#8 Slot the crossbrace into the left main strut

Take the crossbrace (part #10) and slide it into the left main strut (part #5)

#9 Attach the long strut

Attach the long strut (part #6) to the top of the previous part using a 10mm screw. The screw should go through and hold the crossbrace in place

#10 Attach the left rear strut

Attach the left rear strut (part #7) to the rear of the long strut you just added using a 6m screw. It should go on the same side as the main strut

#11 Attach the lower lever

Put the two short lower lever parts (parts #8 and #9) together so that the larger hole is facing to the outside, then attach this to the rear strut you just added using a 10mm screw through the hole at the thin end

#12 Attach the right main strut

Clip on the right main strut (part #11) to the crossbrace

#13 Attach the lower right upper strut

Put a 10mm screw through the lower right upper strut (part #13) at the thicker end and then through the triangular piece (part #12). This piece should be aligned so that the screw goes through the hole marked with a small triangle

#14 Attach the upper strut

Attach the upper strut (part #7) to the upper hole of the triangular piece using a 6mm screw

#15 Attach the right rear strut

Attach the right rear strut (part #7) to the rear hole on the triangular piece using a 6mm screw

#16 Screw the arm on to the base

Take the base you previously built and screw the arm piece on to the centre piece of the base using a 6mm screw. The screw should go through the lower lever and screw into the centre piece of the base

#17 Screw the rear strut to the base

Screw the rear strut to the base using a 6mm screw

#18 Insert the right servo

Slide the right servo in to place so the servo arm slots into the hole

#19 Clip the right servo on

Attach a servo clip (part #14) to either side of the servo and clip it in to the bottom of the base

#20 Wind the cable

Wind the cable around the servo clips to keep it tidy and then plug it into the pins on the base. Looking at the side, the cable should be wound anticlockwise, passing up and over the servo first. The yellow wire should be to the right

#21 Insert the left servo

Slide the right servo in to place so the servo arm slots into the hole

#22 Clip the left servo on

Attach a servo clip (part #14) to either side of the servo and clip it in to the bottom of the base.

#23 Wind the cable

Wind the cable around the servo clips to keep it tidy and then plug it into the pins on the base. Looking at the side, the cable should be wound clockwise, passing up and over the servo first. The yellow wire should be to the right

#24 Attach the elastic band

Place an elastic band around the base, holding the bottoms of the servo clips securely in place. Put this assembly to one side now

#25 Slot the left grip side on

Take the last remaining servo and align the arm as shown in the picture. Take the left grip side (part #15) and slide it on to the end of the servo closest to the arm

#26 Slot the centre grip support on

Slot the centre grip support (part #16) on to the other end of the servo facing the same way as the other end

#27 Slot the grip front plate on

Clip the grip front plate (part #17) on to the front of the two pieces you slotted on to the servo. Make sure the extra hole is at the opposite end to the servo arm

#28 Slot the left grip side on

Slot the left grip side (part #18) in to the third hole in the front plate

#29 Slot the rear grip support on

Slide the rear grip support (part #19) in to the gap and turn it up so it slots into place. The lower edge of it should be level with the front plate

#30 Place the left grip over the servo

Take the left grip (part #20) and place it over the servo arm

#31 Put the right grip in place

Align the right grip (part #21) with the left and hold in place

#32 Slide on the grip base

Slide the grip base (part #22) on so that the large hole aligns with the servo arm side and screw it into place through the right grip with a 10mm screw

#33 Attach the grip to the arm

Attach the grip to the rest of the arm using three 6mm screws

#34 Tidy the cable

Tuck the cable down through the slot on the grip and then in and out of the crossbrace on the arm to keep it tidy and then plug it into the pins on the base with the yellow wire on the right. Put this whole assembly to one side for now

#35 Align the two base pieces

Take the two large base pieces and align them with the white part on top, making sure that the four screw holes are properly aligned. These parts are not symmetrical so it is important to get them the right way around

#36 Attach the HAT to the Pi

Gently attach the Pi HAT to the GPIO pins on the Raspberry Pi, making sure they align properly. Push down gently but stop before it is fully on to leave room for the spacers. Make sure the SD card you prepared before starting is in the slot on your Pi.

#37 Insert the spacers and screws

One by one, take a round spacer and slide it between the Pi and HAT then slot a 16mm screw through to hold it in place. Place the two longer spacers between the HAT and the base ready to screw through.

#38 Screw down the Pi

Gently align all four screws that should be sticking out of the bottom of the Raspberry Pi with the holes in the base and then screw them all into place. Do not overtighten the screws

#39 Insert the front and back sides

Slot the front (part #24) and back (part #23) sides into place. If you have used a Pi Zero, then you should use part #25 instead of part #23 as you don't need the extra holes

#40 Insert the short sides

Slot part #25 into place on the left of the base. If you're using a Pi Zero then there's an extra one of these to fill the gap on the right side of the base

#41 Attach the base cover

Slot all of the tabs on the edges into the cover and attach an elastic on either side of the base

#42 Attach the joystick caps

Push the joystick caps on to the joysticks. It's best to take a look at these and get them aligned properly because there are two flat sides that need aligning

#43 Slide the arm on to the base

Gently prise the two base plates apart and slide the servo arm in between them and slide it down the central slot until it clips into place in the hole in the bottom

#44 Attach the front elastic band

Attach the final elastic band across the front of the base to hold the plates together and make a stable foot to stand it on

#45 Attach the main cable

Plug the two parts together using the ribbon cable included. You're now ready to power up and use your MeArm Pi! First, plug in your power supply to the upper USB socket (the one on the HAT). The power supply should be capable of supplying 2.5A, like the official Raspberry Pi supplies. Once it's moved into its default position you can get started with the instructions here or just use the joysticks to control it. If it's having trouble moving then check the troubleshooting guide for help.