Spot Micro ESP32 quadruped - easy print & assembly

After i was dissappointed about the existing spotMicro projects here on makerworld, i now publish my own. It offers:

• all parts sorted by build step on the printing plate
• no support nor AMS needed
• full assembly guide with images and fitting fully to the printed parts

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Bill of Material

The following Section will describe in detail the different parts needed for your own SpotMicroESP32 build, with at least some rough estimate of the price.

Electronics

The SpotMicroESP32 ist still a Work-in-Progress and as such the BOM might change as well - check the "deprecated" section for changes. There are still some parts missing and some others are not tested yet - those status will be marked as such. I will give a rough price estimate, which may or may not work for you and might be out of date at some point.

Miscellaneous

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Assembly Guide

Prequisites

The single most important thing is to test and to calibrate your servos. By calibration i mean to determin the minimum and maximum positions, and what dutycicle results in what actual angle. Don't use any servos, that behave weird in any way, such as: stuttering, grinding noises, clicking noises or which wont turn at least full 180° - you would regret it afterwards and will have to do a lot of disassembling stuff to get it straight. At last it is important, that you position each servo into a specific position, which will be named in the parts-list in each major step. Depending on where it should be mounted, it results in 2x 0° 2x 60°, 2x 120°, 2x 180° and 4x 90°. Make sure you add all the rubber dampeners to your servos, so you could fit the M3 through the mounting holes. If you wish to use fabric hoses, make sure you use the smallest and thinest possible. There is just not enough space in these parts to use thick ones. Or simply go with the standard servocable, which could look pretty nice, depending on your color theme.

Wrist

You need to make two identical wrists each for both sides - this means, that you need two mirrored pieces for the wrist and wrist counterpiece. Its important that you extend the servo cable and if you use fabric hoses, to guide it through.

Parts

Wrist and foot tip

Insert 2x M3 nuts into their spaces in the wrist. Hold the foot tip at position and screw with 2x M3x8 the foot tip into place.

Wrist counterpiece and ball bearing pin

Insert 1x M2 nut into the small space in the wrist counterpiece. Screw 1x M2x8 through the ball bearing pin and attach it to the wrist counterpiece.

Wrist counterpiece and ball bearing pin

Insert 4x M3 nuts into the small spaces in the wrist counterpiece. Insert now from above the servo into its pocket in the wrist counterpiece. Now push both the wrist counterpiece with the servo and the wrist with the foot tip together, closing all gaps. Be careful not to loose any M3 nuts and screw both parts together with 4x M3x20 screws.

Wrist completed

Your assembled wrist should look like this one. Repeat it once again for the second left wrist and assemble the two mirrored (right-handed) right wrists.

Upper Leg

You need to make two identical upper legs each for both sides - this means, that you need two mirrored pieces for the upper leg bottom shell, upper leg top shell, servohorn mount and ball bearing mount.

Parts

you might use only two M2x8 on each leg to screw the servohorn into place and thus reducing the amount of M2x8 screws and M2 nuts by 2/3

if you have M2x6 then use these instead of the M2x8 which are only in use, because it was easier to buy the screws and nuts in bulk

use the long version of the servohorn & ballbearing mount for improved resting position of the legs or stick to the normal version true to KDY-0523's design for the legs being at an angle when resting

Servohorn mount

You need to screw the M2 nuts on the M2x8 first, otherwise it would hinder the mounting of the servohorn. You can't use the bare M2x8 screws without the nuts in this step, because they would stick out from the other side and touch the servo unavoidably, which would result in blocking the servo movement or other damage. You might consider using M2x6 instead and ditch the need for M2 nuts here completly. Screw the servohorn into place, using the middle hole on each little arm. Make sure that the two arms of the servohorn are perfectly perpendicular to the wrist, when mounted to the servogear at 0° resp 180° (depending which leg) and which arm was on top then. This is because the teeth are not an even number and by this not symmetrical which would either result in a gap between the lower and upper leg when resting or in the worst case, the servo could not rest in 0° or 180° position and always stutter thus pulling more current.

Attach Servohorn mount

Position the assembled servohorn mount to the wrist and make sure that the right arm ist on top. Otherwise remove the servohorn and turn it around as long as it sits perfectly perpendicular and attach it again. Screw the whole servohornmount with a M3x8 to the servo gear.

Attach Ballbearing mount

Push your 625ZZ Ball Bearing into the Ballbearing Mount (it should be are really tight fit). Afterwards push the ballbearing mount on the ballbearing pin of the wrist.

Upper Leg Bottom Shell preparation

Put four M3 nuts in the holes by the servo-pocket and push the servo into place. The two inner nuts are secured by the servo, the two out nuts might fall out so be careful not to lose them.

Route Cables through Upper Leg Top Shell

This part is a bit tricky, especialy when using fabric hoses for the servocables, since the space between the shells is very limited. Route your extended servocable from the wrist through the front hole of the top shell. Pull after that the servocable of the bottom shell servo through the hole as well.

Then push both shells toghether and at the same time pull the cables carfully further through the hole. Make sure the servocable from the wrist goes into both shells through the gap between both shells and is further guided underneath the top shell in the groove specially made for it (marked green). You have also to watch out not to lose the two M3 nuts next to the servo.

Screw both shells together

When both shells are closed you might either move your cables freely back and forth through the hole, in the case you do not use fabric hoses. When using fabric hoses it might be to tight, so you must open the shells slightly, when you want to pull the cables further through.

Use now four M3x20 to screw the servo into place and with it both the top and bottom shell, so they cant come apart without unscrewing them.

Complete Upper Leg

Now with both shell attached to each other and the servocables of the lower and upper leg routet through, place four M3 nuts in the four rear-facing pockets.

Place then both shells on the wrist so that the screwholes in the servohorn and ballbearing mounts align with those in the shells. Use four M3x20 screws, to screw everything together to complete the upper leg.

This is also the robots legs resting position, which results in the legs laying flat.

For the robots normal standing position the wrists servo is at 90° while the upper legs servo is at 120° or 60°, depending which leg.

Shoulder Joint

You need to make two identical Shoulder Joints for both sides - this means, that you need two mirrored pieces for the Shoulder Joint Servomount. This time instead of mounting both on the right or left, each the left and right side will have one of the mirrored pieces.

Parts

you might use only two M2x8 on each servohorn cap to screw the servohorn into place and thus reducing the amount of M2x8 screws and M2 nuts by 2/3

if you have M2x6 then use these instead of the M2x8 which are only in use, because it was easier to buy the screws and nuts in bulk

Servohorn Cap Preparation

You need to screw the M2 nuts on the M2x8 first, otherwise it would hinder the mounting of the servohorn. You can't use the bare M2x8 screws without the nuts in this step, because they would stick out from the other side and touch the servo unavoidably, which would result in blocking the servo movement or other damage. You might consider using M2x6 instead and ditch the need for M2 nuts here completly. Screw the servohorn into place, using the middle hole on each little arm.

Attach Ballbearing Pin to Servomount

Insert 1x M2 nut into the small space in the Shoulderjoint Servomount. Screw 1x M2x8 through the ball bearing pin and attach it to the Shoulderjoint Servomount.

Attach Servohorn Cap to Servomount

Now insert 4x M3 nuts into to pockets in the base of the Servomount and screw the Servohorn Cap with 4x M3x8 into place.

Attach Shoulder Joint to upper Leg

For the robots normal standing position the wrists servo is at 90° while the upper legs servo is at 120° (left legs) or 60° (right legs), depending which leg. Make sure you have actually positioned your servos correctly before, otherwise you should do the movement befor assembling further. When mounting the Shoulder Joint you wont align it to the upper leg along the upper star, but along the first to the right (left legs) resp. first to the left (right legs). Since the servohorn has six arms, each arm means an increase of 60°. For the left legs use this picture as an orientation.

The assembly is straight forward. Take an M3x8 screw and screw the assembled shoulder joint into place, as mentioned above. It is intentional, that the upper leg wont move between both horizontal endpoints, but instead could retract the leg further to the back than to the front.

Attach Servo to Shoulder Joint

Make sure the servos you want to place are at 90°. Place 4x M3 nuts into the pockets for mounting the servo. Place the servo now into its pocket and screw it into place with 4x M3x20.

Shoulder Joint Completed

You have now succesfully attached the Shoulder Joint to the upper leg. With this you have now completed the front left leg. Repeat the steps for the other 3 legs and make sure you use the mirrored parts when building the right legs and the left legs. And keep in mind, that the shoulder joint uses the mirrored parts for the front or rear leg on both sides!

Overview of all of the four legs

With the front left (FL) leg finished, rebuild the rear left (RL) leg with the same steps. But this time use the mirrored shoulder joint piece instead. The picture below shows both legs, where the only difference is the direction the servo in the shoulder joint is facing. Both gears should face outwards towards the nose or back of the robot.

The same applies to the front right (FR) and rear right (RR) leg, with both servo gears facing outwards. Use for the right sided legs also the mirrored copies of the lower and upper leg parts. Keep in mind, that you have set the right angles for your servos prior to assembly, with the servos in the shoulder joint being at 90°, the servos in the upper legs at 60° and the servos in the wrists at 0°.

When all of your legs are assembled the should look like this, with the front legs shoulder servos gears facing to the front of the robot and the rear shoulder servos facing backwards.

Connecting to the Shoulders

you might use only two M2x8 on each servohorn cap to screw the servohorn into place and thus reducing the amount of M2x8 screws and M2 nuts by 2/3

if you have M2x6 then use these instead of the M2x8 which are only in use, because it was easier to buy the screws and nuts in bulk

Screw the servohorns to the outer shoulder piece with twelve M2x8 screws and nuts.

Front & Rear Legs

Screw the front legs to the outer shoulder using two M3x8 screws. Make sure the servos in the shoulder joints are at 90° and that the arms of the servohorn are perfectly perpendicular.

Repeat this for the rear legs as well, so that both outer shoulder pieces face outwards.

The front and rear legs with the shoulder should look like this.

Body

Inner Shoulders

Add into each the top and bottom shoulder block two M3 nuts. Make sure you have oriented the blocks the right way, so that the pockets for the nuts that will be used to hold the covers are facing into the body.

Screw the inner shoulder with four M3x8 screws into place, so that the screwsheads will sink into their pockets.

Chassis

Take the chassis side piece and place four M3 nuts into their pockets - the flat side should face outwards and the long cutout for the circuitry mountingplate should be at the bottom. Chose the mountingplate corresponding to your bigger buck converter - the XL4016 or SZBK07 https://github.com/michaelkubina/SpotMicroESP32/tree/master/electronics

Put your (pre-populated ???) circuitry mountingplate between both sides.

Now attach both inner shoulders to it with each four M3x8 screws and the bigger blocks being at the top.

The assembled chassis should look like this.

Mount legs to chassis

Attach now the ball bearings to your shoulder joints. Put into the front of the top and bottom shoulder block M3 nuts. Screw the front legs assembly to the shoulder block with four M3x8 screws.

Repeat the steps for the rear legs as well.

When finished, your SpotMicroESP32 should look like this.

Head with ESP32-CAM

Place the ESP32-CAM into the designated place of the Cameramount. Screw the counterpiece with two M3x8 screws into place, with the small pads facing towards the ESP32-CAM thus preventing the PCB from lifting. Place now the two HC-SR04 into their spaces in the sensormount-piece, but dont push them all way down yet. Instead leave some half centimeter space.. Push now the Cameramount-piece on top of if, so that the wedges slide on top of the HC-SR04 PCBs, thus preventing them from slipping back out again. It might be necessare to hone down a small portion of the lower ends of the wedges.

Place now four M3 nuts into the spaces in the front cover, push the sensor- & cameramount into place and screw all of it with four M3x8 screws into place. The head is now assembled.

Tail

The following section needs to be redone as the referenced piece is currently deprecated 😅

Mount TFT Screen and Pushbutton

Place the 1,8" TFT with SD-Card into its designated pocket and screw it with four M3x8 screws into place - counter it with four M3 nuts from behind.

Remove the nut from your pushbutton and slide it through the hole - counter it with the nut again from behind.

Your rear cover is complete.

Top and bottom Cover

Connect both cover halves

Take the front and rear half of the top cover. Use four M3x8 screws to screw both pieces together - counter them with four M3 nuts.

Repeat this for the bottom cover halves as well.

Mount covers

In order to mount the head-unit, the tail and the top and bottom cover to the body, you need to add the M3 nuts into the top and bottom blocks in the front and rear shoulders (highlighed green).

Mount Head

Slide the assembled head-unit onto the front shoulder-plate.

Screw it from the top and from the bottom with four M3x8 screws into place.

Mount Tail

Slide the tail onto the body as well and screw it with four M3x8 nuts into place.

Mount top and bottom covers

Place the bottom cover beneath the body and screw it with four M3x8 into place.

Place the top cover over the body and screw it with four M3x8 screws into place.

Assembly Finished!

Congratulations, you have now succesfully assembled your SpotMicroESP32.

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Electronics

Wiring

When wiring your own robot, think of some kind of color coding for your wires, so its easier to distuingish them - for example:

• 5V with violett wires
• 3.3V with red wires
• I2C Clock white
• I2C Data grey
• Analog Signals ocker
• etc...

SERVO DRIVER - PCA9685

Manufacturer Homepage: https://www.nxp.com/products/power-management/lighting-driver-and-controller-ics/ic-led-controllers/16-channel-12-bit-pwm-fm-plus-ic-bus-led-controller:PCA9685 Datasheet: https://www.nxp.com/docs/en/data-sheet/PCA9685.pdf

The PCA9685 is capable of FastMode+ (I2C clock at 1Mhz) - it should have its own I2C bus - which gives us more update cycles on the servos. The MG996R even though most tutorials and sellers claim their working frequency to be 50Hz, we can actually go to even 333Hz and beyond. The limit is only the 12Bit resolution and the maximum value for your servo for the max-angle. The pulsewidth of about 2ms + about 0.3ms is whats relevant for the IC in these digital servos.

Do not use Standard Mode - 100KHz Do not use FastMode - 400KHz Go with FastMode+ - 1MHz

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Code

https://github.com/Blacksheep909/SpotMicroESP32-Nitro-Fork/tree/master/code

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Source

https://github.com/michaelkubina/SpotMicroESP32

credits to: https://github.com/michaelkubina