Bolt Bots - Micro Servo Droids

Minimal Hardware 4-5x servos + Wireless Control

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It started as a walker but I think of the project as some simple robotics kits.
The same electronics + a few printed parts.

Micro Droids based on 4-5 servos.
V1 - 5x 9g servos 4 leg walker
v2 - 4x 1.8g servos nano walker
v3 - 4x 9g servo 3 axis + tool end arm
v4 - a car 2x continuous rotation servos + 2x servos
v5 - hanging drawbot

Based on the same Arduino Micro + nrf circuit.
Simple 3D printed Designs - many parts can be laser cut for faster/cheaper batch parts.

The first challenge for the hackday prize is Re-engineering Education. With that in mind I started working on a micro servo quad leg walker robot that I had a basic design for. Updated the design to be fully printed.

All the variants use the same base electronics/hardware.

  • 9g micro Servo < $2 each
  • 9g 360 rotation Servo < $6 each
    • servos = $10-30
    • Printed bits = $20?
    • Screws, wires, small bits = $5
    • Controller = $15
    • Battery = $10
  • final cost < $100 per robot/project

This project hits all the basics and can be useful at various levels.

  1. 3D Model Design/ Printing
  2. Arduino Programming C++ or Scratch
  3. Hardware Pcb/wiring power

Like a lego robot but better than lego.

Erector/meccano type printed parts are an easy thing to make and keep spares to finish off or at least test out an idea.

Finally passed the scorpion again, and made it to the finals!

Did get a feature, cool. 
This Hackaday prize entry from [Saul] is the beginning of a reconfigurable kit of 3D printed parts and servo motors for robotics learning. With just access to a printer, a few cheap-as-chips servo motors, an Arduino, and some nuts and boltz, you could be hacking together robot walkers within a few hours of starting!
  • V1 Remote Control -  4 leg walker - I Can write the code to make walking easier, but do I need to?
  • v2 Micro walker
  • v3 4/5 axis Robot Arm - Dumme doesn't have a point...
  • v4 RC Rock Crawler Truck - Steering needs last bits, tank/pivsteering combo stuff
  • v5 Hanging Drawing Robot - This is giving me problems. but time for whiteboard tests.
  • v6 Bubble bolt - Rotary wand + Coreless ducted fan + maybe toroidal props for low noise
    • I regret calling this a bolt now, but it will probably be the most fun
    • maybe a servo and accordion fan could work

The more I make the more I need to document, so I think thats it for now.

Just a video with all the current boltz in one...

Standard Tesselated Geometry - 504.18 kB - 04/07/2023 at 06:35


Standard Tesselated Geometry - 387.19 kB - 04/07/2023 at 06:35


Standard Tesselated Geometry - 152.04 kB - 04/07/2023 at 06:35


Standard Tesselated Geometry - 113.56 kB - 04/07/2023 at 06:35


Standard Tesselated Geometry - 92.07 kB - 04/07/2023 at 06:35


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  • idk...

    Saul2 days ago 0 comments

  • not a bot.

    Saul05/14/2023 at 21:13 0 comments

    • V2 - Micro I did test and got it moving with the microRF.
      •  but these tiny linear servos are not as reliable and cost 10x more
      • its a cool demo but going to cut it off at prototype
      • Similarly i'll resist trying to upsize the walker anymore.
        • mostly likely need to go back to shorter legs on the wide frame to help reduce flipping
    •  stick to low cost 9g servos. and 360 9g servo "motors".

    I decided that the car is not robot enough to fit into the project.

    1. Uses wheels/tires/shell that add to cost
    2. Used different size screws, aside from the servo screws.
    3. not a robot.
    4. this new version is more fun. 

    Bringing back my roller Droid with updates to stay in the rules.

    • The rz7 used tiny metal geared dc Motors. + L293d dual h bridge
    • This version uses 360 servos.
    • Keeping the regular servo for later..
    • First made some new wheels near the max of my current printer. 100mm
    • then widen, and rotate the frame to gains some space for battery/controllers

    I think I will add i2c ports to the 10x pico board for extra sensors and expansion, but the picoW will still have a enough unused pins to add other bits for now.

    Even tho the challenge was Education based, I'd like to keep some experienced hackers' attention also.

    This isn't really a balancebot., its more of an unbalanced rotations that made the early version fun.

  • PicoW x Bolt = 10X Servo board

    Saul05/13/2023 at 21:12 0 comments

    • it would be okay for college but soldering in schools seems risky
      • Try to make the electrics "plug and play"
    • 10 Channels is plenty to have a full motion Dog, or hexapod, plane maybe...
    • $11 electronics base.
      • 21.6 x 30.2 mm = 1 inch squared. $5.00/3 = 1.67
      • +picoW = $6
      • + maybe $3 for power input stuff...reg for 3-4x AA/C/D cells.
      • + printed Frames (need to estimate costs)
    • I think I have enough space to include a breakout for 2 analog lines for testing.
    • Power cap is wrong. and could use a switch or screw block.
    • maybe this will get a speed upgrade like my last order from oshpark.

    Existing Control options:

    1. 8-Channel PWM or Servo FeatherWing
    2. Adafruit 16-Channel 12-bit PWM/Servo Driver - I2C
    3. Pimoroni Servo 2040 - RP2040 18 Channel Servo Controller

    This should work as a Single Layer PCB!  we really only need 1 ground line to the pico...

  • Procrastination Projects...

    Saul05/13/2023 at 16:44 0 comments

    When do we do our best work? When we were trying to work on something else...

    Needed to waste sometime until the round 1 finals were announced.

     Work-hack - Can not take code from another project, if you didn't already put the work in.


    This gave me a reason to work with an imu past the examples. and since a few Ultrasonic sensors were on my desk, they got added in.


    This project is almost popular enough to continue on its own, for now its a back burner/bubble bolt parts bin.

    Hackaday Prize 2023 Round 1 Finalists  I found out on youtube!

    thats about 2k more views than I remember, did I get featured? 

    Made the Cover Pic! Checking out the other finalists to figure out what/why made it.

    1. Concept > Cost - Reducing cost is something on the timeline but first you need to create Value.
    2. Purpose > Popularity - with the goal in mind, We need some popularity in the end to consider the project successful, But whats the point it didn't Really teach anything?
    3. Round 1 Advantage. Now I have a huge time advantage over later round entries. but they get to learn from the previous round entries...

    Bolt update: Taking the udp/android-arduino code from Censored to reduce the Electronics cost.

    1. Pico /Pico W base control have a few benefits over the microRF.
    2. Down side is the added requirement of an Android device.
    3. Upside - Less cost, more servo Channels, more program memory. Python Support + Android Development
    4. Bubble Bolt coming soon.

  • Can you guess the next bolt?

    Saul05/12/2023 at 06:03 0 comments

    Converted the drawbot to a picoW controller but still seeing some servo problems...

    Taking a ducted motor from another project and one 360 servo. 

    • The wands could be printed but they are so very slow, and probably won't work as well as the injection molded version.
    • Almost no logic needed, maybe add a rotating base and "sonar" ...

  • hardware mode

    Saul04/25/2023 at 15:19 0 comments

    Got stuck on a dumb error for a while then found some weird interference problem....

    • 32 slots -> flipping 64 times a rotation. Maybe I should go down to 16/32 for now.
    • but If my quick math is right each notch = pi mm travel. 
    • if it works it would make the repeatability near a stepper motor.

  • Drawbot and Car

    Saul04/21/2023 at 07:58 0 comments

    • The drawbot arm turned out nice and almost perfectly placed considering it was the last thing I designed.
    • Will probably switch 2/4 idler pulleys to loops to help keep the strings in place better.
    • Needs a part to slide against the board while the pencil is up.
    • I have not tested precision yet. drawing is based on the servos rotating predictably enough.
    • to add precision I was thinking a few magnets on the main pulleys and a hall sensor.
    • Or using a couple of ir - end stop switches and a Tone Wheel should give better resolution with less weight than magnets.
    • needs testing but should be a decent option and only need 1 pin per axis.
    • Ran out of torque on 4V lipo. swtiched rx to 5V input.
    • Drawbot weight is about 75g + 20g rx/wiring... about 100g pull from 9g 360 servos.
    • main wheel is ~100mm C = 31.8 mm Dia.

    If you flip the drawbot a Scara style arm is another design option I probably won't work on yet...

    The steering arm blocked the front body mount, which was the reason for making the front width more to clear the body..

    • without the body it will drive upside down.
    • full suspension version is probably possible
    • had to upgrade the center frame to using all 6 mounting holes.
    • easy 1 part frame on a Standard size printer.

  • Just an Idea...

    Saul04/18/2023 at 23:00 0 comments

    Probably will not happen. for sure not the right scale.

    • But a couple brushless scorpions might have enough Payload to carry Walking Landing gear!
    • I guess a regular quad/tri drone would work also. but 4 pivoting props would be interesting.
    • *brushless versions of the scorpion will run on the same bolt bots controller. 
    • There are some small brushed escs that would work also...

  • V 4-6 RC Rock Crawler

    Saul04/17/2023 at 12:41 0 comments

    A frame for a basic rc car/truck rock crawler turned into a drawbot.

    • 2 9g continuous rotation servos as main drive.
    • Pivot arms need some work. dual idler pulleys for alignment.
    • speed is pretty good.
    • moving down/ horizontal is a bit difficult.

  • working prototype.

    Saul04/16/2023 at 13:51 0 comments

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