How to Build the One Motor Walker!




Introduction: How to Build the One Motor Walker!

About: I am a French Canadian that loves robots and embedded electronics. I work on all kinds of cool projects, like a high-power electric push scooter controlled with an Arduino. Please visit my website for more co…

Here is Instructables on how to build a walker with only one motor! This design is base
on the principal of B.E.A.M robotics! Building simple and elegant robot inspired by insect.
This robot was build back in 2000 and want to show you how to build it.

Beware this is a complex project!

This project incorporate two more instructables
How to modify a servo motors.
How to make the bicore circuit.
( I still did not learn with those truncated title :P )

Here are the 3 most important steps in this Instructables

step 1 - Read carefully!
step 2 - Read again before asking questions, check the comments!
step 3 - Did you read? if not goto step 1

PS- My instructables don't even contain a lot of text! Just pictures! :)

To be able to make this robot you need skills.
You will need to solder electronics components.

Gareth Branwyn once contacted me to make a article in his book about my one motor walker.
The chapter is online. This is worth reading in parallel while making the robot.

Solarbotics made your life easy by making custom bundle for you!
I don't think there is a big gear is in there. Be careful.

If you never build a robot and want to tackle the one motor walker, I suggest you try the beetle robot.

Good luck!


Don't forget to check my website to see my latest projects!

Step 1: How to Build the One Motor Walker!

Here is what you need to build this walker.

Items for the robot:
1 x Servo motor with servo horn
1 x Terminal block
1 x plastic gear ~2 inch
1 x plastic servo horn
1 x 2 feet of 8 to 10 gauge wire ( can use coat hanger wire or 10-gauge copper wire )
1 x short piece plastic tubing ( can use the isolation from the 8-10 gauge wire )
2 x AA or AAA battery holder

You could use the GM8 from solarbotics
don't forget this

Items for the BICORE"
2 x .22 µF monolithic capacitors
1 x 100K to 10MΩ resistor (we recommend 3.2MΩ)
1 x 74HCT240 integrated circuit (IC) 74AC240 will be better
1 x 20-pin DIP IC socket
1 x on/off toggle switch (smallest you can find)

the recommended tools for this project:
1 x safety glasses!!
1 x soldering iron
1 x glue gun
1 x wire strippers
1 x side cutter
1 x scissors, knife, x-acto, etc

I recommend you to take the time to read this entire instructable before starting. In every page I have added a lot of pictures, so don't forget to look.

Step 2: How to Build the One Motor Walker!

This is main mechanical part you will need to make the robot.

You can find this sort of gear in VCR. Search garage sale or ask familly and friends.
The DVD is already obsolete thank to the BluRay, imagine how obsolete is the VCR! :P

The gear in the picture is from a VCR.

If you are really lazy, you can buy it from there

Step 3: How to Build the One Motor Walker!

Glue the servo horn to the plastic gear. Be sure both hole are aligned.

You can use traditional servo horn for this project. It will work.

Step 4: How to Build the One Motor Walker!

Please visit this instructables to know how to modify a servo motor

Step 5: How to Build the One Motor Walker!

Here you are building the pivot rod for the front gear.

I took a coathanger and bend it like the second picture.

You simply glue it in place.

You can use cooper wire to do the same thing. Look at step 8 to know which wire to take.

Step 6: The Front Gear

Find a rigid plastic tubing that fit over the coat hanger. This tube is your pivot.

You can use the plastic that cover a electric wire. Maybe some 14/2 or 10/2 wire will do.
Read step 8 to understand what does 14/2 mean.

Step 7: The Gear Assembly

This is a easy step. You insert the front gear into the metal rod.

Bend the rod so both gear touch. This is really important.

To secure the gear, look at the step 9. I use terminal block to hold it place.

Step 8: The Legs

Find some 14 gauge cooper wire. It is normally call 14/2 or some will say 2/14
8 to 10 gauge will work too.

14 is the gauge ( the size, the diameter of the wire )

22 gauge is breadboard wire and gauge 0 is the size of your finger! 200 Amp

2 is the number of wire not counting the ground. You have a black and white wire.
The black wire is the "hot" that carry the 120V

14/3 is the same with one more wire. The wire is red. You normally use this wire when you have
a 3 way. Two switchs that control one light for example.

You can use a coat hanger to make the legs.
I recommend adding to some heatshrink to the end of the led to have better grip on the floor.
You can see on the video, the robot slips a little bit while walking on the table. There is no heatshrink on my robot, only rigid plastic tube.

Step 9: The Battery Holder

I use AAA batter holder but AA will do the same. Glue them to the servo motor.
We will hook are battery holder in serie to get higher voltage but with the same current.

Four battery of 1,5Volts will give 6V of power.

If you use rechargeable battery it will be 4,8Volts

To hold your gear in place, I have use some terminal block, I have remove the plastic and cut the terminal in two using a saw. I simply put them on the shaft to hold the gear.

You can even use small tie-wrap instead of terminal block.

Step 10: The Circuit

This is a the hard part if you never made electronics.

Please visit this instructables to make this circuit

The schematic is really ugly and was made ~7 years ago with paint!
The 74AC240 circuit come from

R1 = 1Meg Ohm
the capacitor are 0.22uF

Step 11: How to Build the One Motor Walker!

Glue the circuit on top of the servo.

Hook up the motor to the circuit like the circuit.

Step 12: How to Build the One Motor Walker!

You robot is finish.

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    4 years ago on Step 12

    I love it! This is a very well done project!


    4 years ago

    Wow! It fits to my snack-bot project! Imagine: some segments of One motor walkers to build the snack's body! Or a dragon! ( yeap: a mask of latex for skin would be nice!)... so, am I the fricking nerd, or not?


    5 years ago

    which type of capacitor did u used......??


    Reply 5 years ago

    ceramic capacitor


    6 years ago

    What is the circuit for and why do we have to glue?

    goyaam jaim
    goyaam jaim

    7 years ago

    hi robomaniac can u plz. explain me the working of bicore used

    Can we get the gear in a sewing machine???????
    My mother's one has failed.....................


    Reply 13 years ago on Introduction

    nope, it does not have any sensor. It can not backup. I am working on a other version that could turn and seek light.


    Reply 12 years ago on Introduction

    hello jerome , ummm.. there is a problem in my circuit the motor oscilates more on one side than the other i checked everything but nothing was wrong in the circuit any idea why ?


    Reply 12 years ago on Introduction

    hello, that is normal due to the fact that it is a bicore. Mine does the same thing. That is why I have a mechanical stopper ( the nail ). You can change one capacitor and try again. You could try to change both cap. Thanks Jerome


    Reply 12 years ago on Introduction



    Reply 12 years ago on Introduction

    hello jerome , I took some pics of rahil - the one motor walker


    Reply 12 years ago on Introduction

     Hello sid..
    well i liked ur robot.
    Also i have the same problem as u have that it tends to rotate to one side more than the other.
    so how did u manage to make it almost perfect synchronism.


    Reply 12 years ago on Introduction

     hello ,
               I think you might as well check for capacitor connections you cannot get it perfectly stable so the best idea is to uses a spring or rubber band as jerome told .i found that it really helps. also found that a little left or right movement doesn't affect much of the walking gate. you can use a nail or a paperclip to stop excess movement most beam bots have these springs attached to them both my robots use a spring mechanism the last picture is of mark tilden's famous spyder which also has the springs built in. to give suspension and a controlled step


    Reply 9 years ago on Introduction

    The bottom pics are AWESOME!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!