Introduction: BoB the BiPed

Picture of BoB the BiPed

Did you buy an arduino after seeing all the cool instructables and now you tired of just making LEDs blink? Are you envious of all the cool walking robots people are building but don't have the experience or cash for all of those servos and expensive brackets? Here is your solution meet BoB the 4 servo mini biped robot. Bob is both easy to build and very cheap to assemble and yet is loaded with personality and endless expansion capabilities.

So how did BoB come to be?
After wanting and drooling over all the 3d printers(still don't have one) and cool stuff being built. i was offered and opportunity to design a robot and have it printed for me and so bob was born.

What are future plans for BoB?
First i would like to explain a bit about my school experience. When i was younger i dreaded school in fact the only thing that got me through the day was my tech classes. They made school enjoyable and let me into the robotics hobby i actively participate in today. Using BoB i would like to give back. The first BoB was created due to a very generous offer and since i have made many improvements. But without a printer to test each design they are just untested files. My long term Goal is to make BoB into a cheap and easy to assemble class room activity to help children get their feet wet in the world of robotics, to give those hands-on kids like me something to look forward to, and to give them an introduction to new technology that is making waves and if the future in many fields. so my next goal is to attempt to obtain a printer be it by winning it, building it over a period of time (my funds are very tight i have a child of my own) or raising the money to continue my work.

so are you ready to build?

Step 1: Collect Your Parts!

Picture of Collect Your Parts!

the printed parts for bob can be found HERE
and the original build page HERE
the parts are currently at version 2.0 while they look different then the prototype pieces in this instructable. Assembly will be the same as only cosmetic changes were made. I will update with the newer version if and when i get a printer.

Parts you will need:
Printed parts set (settings used to print proto pieces can be found on thingiverse page)
4 9g micro servos
4xAAA battery pack (or any suitable power source)
parallax ping sensor(optional, also updating files for cheaper alternative)
micro controller of choice (smaller is better)

Tools needed:
phillips head screw driver
nail file or sand paper

Step 2: Assemble the Legs.

Picture of Assemble the Legs.

my robot was already assembled and taken apart for this instructable..this is where i fail and couldnt find my small screw driver to fully take down the legs. i have provided as many pictures as i can.

step 1: center the servos!
for arduino connect the servo signal cable to D9 and the servo pos and neg to 5V and Gnd on the arduino.
open up the arduino IDE and type this in

Servo servo;

void setup()
servo.attach(9); // attaches the servo to digital pin 9

void loop()
myservo.write(90); //tells the servo to go to the center position

do that for each leg servo and assemble like in the pictures

Step 3: Time to Get Sandy!

Picture of Time to Get Sandy!

even the best 3d printers make parts that need a little fit work so...Get sanding! 
i personally use a nail file, course side first, finer grit after. sand some then test fit and keep doing so until it all fits together nice.

the two areas that will need work are shown below...the holes for the servo and ping sensor (if your using one)

after all your parts are fitted slide them in and secure..i made mine fit without the use of screws (but the screw holes are there to use!)

Step 4: Mount His Brain!

Picture of Mount His Brain!

where you mount the micro controller is entirely up to you. the one i chose to use was a bit to big to fit internally a small controller like an arduino nano or pro mini will have no problem fitting in the head. my solution was to drill two holes and mount the board on standoffs to the back of the head

Step 5: Wire It Up!

Picture of Wire It Up!

run the wires from inside (battery pack, servos, ping) out of the extra hole in the base. and plan your connections...i take a piece of paper and lay the connectors out and label what they are and where they are going. just pay close attention to the polarity of the connectors. this is where the micro magician shines as all the pins are broken out to servo style connectors.

Step 6: Program It and Let It Go!

Picture of Program It and Let It Go!

hook all the wires up and open the arduino IDE. 
load the code found HERE and make the changes needed. it is a well comment code and credit goes to LMR member Protowrxs for his awesome code

the changes to be made will be pin assignments as well as minor tweaks to center the legs and feet 
first find the part of the code in the first picture the first line of each group assigns the pins to the servos change those to reflect you setup

and the second picture shows the group that lets you tweak the servo positions change the first of each group to numbers that let BoB sit straight and level

after all that is done..load the code and let him rip! BoB will walk forward and if a sensor is attached he will walk until an object stops him and then avoid anything that comes near him.

Step 7: The BoBs Around the World

Picture of The BoBs Around the World
the BoBs on this page have been made by people all over the world. and are just a few around. 
most come from members of  and they are doing some amazing things.

this first video is of LMR memeber jax's BoB dancing as he claps

Step 8: BoB Multimedia + Future Plans

Picture of BoB Multimedia + Future Plans
here i will post videos and pics as bob improves

here's a short video of BoB walking...kind of. my batteries for him were dead so i mounted a lipo pack to the top of his head and it threw off his COG(center of gravity) making him walk poorly, i also see that without a very smooth walk cycle he tends to slip and slide. 

Future Plans:
Future plans include giving BoB a voice (even if its just beeps), giving his feet some traction, Bluetooth control, a 6dof upgrade called RoB, an arduino Board backpack that can be screwed in to existing holes so no drilling is needed...and lots more...each will get its own instructable!

Thanks for taking the time to read


Ameerhafizin (author)2017-05-28

Can i use arduino uno

mrtkaya (author)2017-04-14

code please?

cparrapa (author)2016-11-17

Thanks for this opensource project Otto DIY was possible!

bigred0304 (author)2016-05-25

I'm looking to make ac couple of these guys in my Electronics class. But I don't seem to be able to get hold of the original code for the nano. I found one that will walk but doesn't incorporate the avoidance. Has anyone got a link to where I can get the code please?

Hulkco (author)2016-05-23

Nice project, thanks for share!

bonnetx made it! (author)2016-05-07

Very simple and efficient walking cycle for bob :

void loop()
// Walking, turning, or rock and roll walking (Citation from H. Hansen :-))
F=25 ;//25 Amplitude of the ankle movement
R=30;//30 Amplitude or the hip rotation movement
dt=10; // delay between each time loop
pulse=F*cos(t/100.0*2.0*3.14); // just a cos
pulse2=R*sin(t/100.0*2.0*3.14); // just a sin
myservo1.write(POSA+pulse2); // (hip rotation) if you change pulse2 by pulse2/2 it will turn right
myservo2.write(POSB-5+pulse); // inversion eversion of the ankle
myservo3.write(POSC+pulse2); // (hip rotation, the other leg) if you modify + by - he will turn also
myservo4.write(POSD+5+pulse); // inversion eversion of the opposite ankle (the minus sign is just due to contruction)

if (t>100) {t=0;}

KunalC (author)2016-04-24

sir i have a dought can uh plz say me how to connect these servos to arduino mini..

thanks in advance

DmitryM8 made it! (author)2016-04-23

Used the code for ICBob and modified it slightly. Balance is fine with Ni Cd battery (6v).

MorganeC1 (author)2016-02-29

Hi, I'd like to try this project as well but unfortunately can't find the code going with it. The link is broken... Where could I find a code ? :)

3DLirious (author)2016-01-15

The link ( ) to the Arduino code is dead. Does anyone know where a copy of this code can be found?

k.biagini (author)3DLirious2016-01-16

There are some files on the thingiverse page for a software/code combo to get you going. Let me k ow if that helps. I will update the intructable later as well with the zip file

3DLirious (author)k.biagini2016-01-17

Thanks; I saw the Poser code but was really looking for the standalone Arduino code. If you could post it that would be great! :)

blic19933 (author)3DLirious2016-02-11

If you are still looking for stand alone code for your Bob you can check out our instructable

It has some code to get you moving. Don't forget the VarSpeedServo library

3DLirious (author)blic199332016-02-23

Thank you, that project looks great! I will definetely try it out when I have some time. :D

Slk_Stephane (author)2016-02-17

Hey! my computer doesn't detect DAGU MINI MICROCONTROLLER?

I need HELP?

teknohawk (author)2015-08-01

That is so neat! I like how aesthetically pleasing and simple it is, yet its functionality and potential is seemingly endless. Good job man!

k.biagini (author)teknohawk2016-01-16

Thank you very much

ruizfc (author)2015-07-22

my code wasnt compiling as well. So I removed the "serial.h" liberie (since it is not being used) and then the code worked =)

aaroncampbell (author)2015-07-03

Has there been the code for hc sr04 been released yet?

AdityaS9 (author)2015-05-15

The code u given was not compiling can u help me please

Arduino Tech (author)2015-04-25

I have hc-sr04 ultrasonic sensor distance sensor instead of the ping sensor what changes are needed in the code ??

josephmilla (author)2015-01-14

What's the difference between v1 and v2 files?

k.biagini (author)josephmilla2015-01-27

v1 is the featured robot. v2 is just visual changed and is assembled the same way..just some more rounded edges

3dprinterkid (author)2015-01-04

Before purchasing electronics I would like some help. I would like to control BoB with a ps2 controller. What setup should I use? Would a Lynxmotion ps2 v3 controller and botboarduino work? Also, when websites say that you can power the logic port and/or the servo port (for your control board), what does that mean? which one would I use for BoB?

Thank you so much,


Tchello (author)2015-01-03

I'm finishing mine however there is something that I want to know before.

I'm using a 9V battery as energy source for an Arduino Nano that I'm using, should I use an external power source for the servos or is it ok to wire everything to the Arduino 5V pin? I thought about an external feeding circuit from the same battery with a power regulator at 5V, what do you recommend?

k.biagini (author)Tchello2015-01-03

Do not run the servos from the 5v pin they will run fine from the battery if it can supply enough current. A 4xAAA pack fits snug in the ripoff the head and is enough to run the servos. I have also worked on feet with battery packs built in. I will do a new instructable soon with the new designs

gadgetnerd3373 (author)2013-12-29

I personally made my own version with limited parts ( BoB minus the Ping sensor ) it's mostly made of cardboard and held together by duct tape, mostly because i'm 15 and don't have a 3D printer.

INSTRUCTABLE COMING SOON!!!!!!!!!!!!!!!!!!!!

Tchello (author)gadgetnerd33732015-01-03

I liked your spirit, I did the same in the past with very limited resources.

Have you been doing any new project lately?

Wish you the best.

k.biagini (author)2014-12-14

sorry didnt see this i just used the servo screws to mount everything and the head was a friction fit or you can use extra servo mount screws

k.biagini (author)2014-12-07

If using a aaa pack you need almost 8 batteries a AA pack fits in the back of his head or use a rechargeable 9v battery

3dprinterkid (author)k.biagini2014-12-09

Thank you!

JasonRP made it! (author)2014-08-03

Thanks for making this project available.. I finally finished my version tonight!

sweaving (author)2014-07-09

Another Bob

sweaving (author)2014-07-09

I have just made one of these! will post some pics soon, i also wrote the walk avoid code myself as a learning curve! so far he can walk forwards, backwards and turn to the have modded the CAD

so an arduino nano can be fitted to the head with acces to the USB port.

i Have to say Bob is a great little Bot!

makesomeso (author)2014-03-03

nice robot. i like bob and im gonna make it !!

JasonRP (author)2013-08-21

Anyone know where I can by the plastic parts for this robot?

k.biagini (author)JasonRP2013-08-26

you can look for a local makerspace...or any of the online print shops..BoB is on shapeways but they charge about $ can also look at the 3d printer forums there are members there that help other without printers

k.biagini (author)2013-06-18

thank you all for the support bob got first in the pocket electronics contest i am truly grateful!

emilyvanleemput (author)2013-06-14

Really cool!

thank you :)

You're welcome!

gururise (author)2013-06-06

Do you have a working head for use with the cheaper HC-SR04 sonar sensor yet?

k.biagini (author)gururise2013-06-07

as seen here

k.biagini (author)gururise2013-06-06

i was told that with a little bit extra sanding, that it fits.

Michael_Bell (author)2013-06-04

Cool! I voted for you in the 3d/Epilog Challenges! I don't know how I missed this for >10 days

k.biagini (author)Michael_Bell2013-06-04

thank you very much for the votes!

Alderin (author)2013-06-03


I've had 4 of these servos around for months, pondering how to put them to use, and I think I've just found it! Very cute design! With only 4 servos a standard Arduino can do all the positioning with analogWrite(), leaving the digital I/O pins and one analog I/O pin free for other uses! The 'head' won't fit a full-size Arduino, but since I'm going to build the legs from popsicle sticks mine will end up just being a walking Arduino.

So excited to start this build! (Yes, I'll photo-document it!)


k.biagini (author)Alderin2013-06-03

the fact that a regular arduino doesnt fit in his head was one down side. but can be remedied by mounting it to his back and running all the connections inside. i did that with my Dagu Micro M and it doesnt affect the center or gravity enough to matter. you idea has given me one and arduino biped shield! thanks for taking the time to look and thank you for the vote!

Alderin (author)k.biagini2013-06-04

The "Moteino" would probably fit, and has built-in wireless ability (though not BlueTooth). As for a biped shield, without stacking it would be easy and cool, but not very extensible. Building it stackable would be a challenge. A biped shield plus turret shield or ping shield or IR shield would be very cool.

Stackable... My brain starts on a line of thought with built-in battery pack with separate power feed for the servos, 5dof (2d hip, 1d knee, 2d ankle) legs with a separate MCU doing the servo control to take fewer of the lines from the Arduino, maybe use SPI so that even the lines that are used aren't "used up", preserving the shield stackability. But I hear my "grand plan" alarm buzzing as I type this. :-)

k.biagini (author)2013-06-04

bluetooth stuff came in today look for the bluetooth BoB tutorial later today!

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