Picture of A Servo-based 4-legged Walker
Build your own (needlessly tech) servomotor-driven 4-leg walker robot!

First, a warning: This bot is basically a microcontroller-brain version of the classic BEAM 4-legged walker. The BEAM 4-legger may be easier for you to make if you aren't already set up for microcontroller programming and just want to build a walker.

On the other hand, if you're getting started with microprocessor programming and have a couple servos kicking around, this here's your ideal project! You get to play with walker mechanics without having to worry about the fussy analog BEAM microcore tweaking.

So although this isn't really a BEAM bot, the following two webpages are great resources for any 4-legged walker:

Bram van Zoelen's 4-legged walker tutorial has a good overview of the mechanics and theory.
I took my leg design off his website.

Chiu-Yuan Fang's walker site is also pretty good for BEAM stuff and some more-advanced walker designs.

Done reading? Ready to get building?
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Step 1: Gather parts, measure, plan a bit

Picture of Gather parts, measure, plan a bit
Making a 4-legged servowalker is pretty simple, parts-wise. Basically, you need two motors, legs, a battery, something to make the motors go back and forth, and a frame to hold them all.

Parts list:

2x Tower Hobbies TS-53 Servos
20in heavy copper wire: 12in for front legs, 8in for rear. I had 10-gauge. 12-gauge should work, but I'm guessing.
Battery is a 3.6v NiMH that was selling for cheap online.
The microcontroller brain is an AVR ATMega 8.
The frame is Sintra, which is hella cool. It's a plastic foamboard that bends when you heat it up in boiling water. You can cut it, drill it, matte-knife it, and then bend it to shape. I got mine at Solarbotics.

Other parts:

Drilled project board for the circuit
Snap-off headers (male and female) for the servo and battery connections
A 28-pin socket for the ATMega
Super-duper glue
Soldering iron and solder, wire
Some tiny bolts to hold the motors on
Matte knife

Here, you see me measuring out the parts, making a sketch for the frame, and then grabbing a ruler to make a paper template. I used the template as a guide to mark with a pen where I'd drill holes in the Sintra.

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JackT26 months ago

Well done mate ! interesting project really. It's simple but effective! Thanks for sharing.

jaristotil1 year ago
Is this circuit needs a clock between 9th and 10th pin?
veysi4512 years ago
i wanna use pic16f628A ; can youu send me pic program and circuit diagram. thanks... is my adress.
geeklord6 years ago
I need to learn how to write in C. Can I use C to programall microcontrollers??
fibean geeklord2 years ago
Yes! With AVR's you can use AVRStudio (free, made by Atmel) to compile your C code into an .hex file, ready to upload on avrdude.

You can take a look at the datasheets, there you will find information about the microcontroller. You will find C code examples in the datasheets too.

To find the datasheet of the microcontroller you want, take a look at Atmel's site (for AVR's), or try to search on google something like "ATMega8 datasheet". It may be on the first results.

You can't use C++ in microcontrollers, btw.
Nope. I tried uploading C++.

C++ = busted Arduino (if you're using one.)

Try getting the Turbo C bible...worked for me.
kperfect2 years ago
can u give me neat cicuit daigram to my mail
krogie5 years ago
How much would it cost if I want to build oe of these?
It depends on what you have laying around. If you already have soldering equipment and plan on going ghetto for the programmer, I would say around $20-$25.
ahh, i have two servos, an msp430 launchpad, I just can't figure out how to get them to talk to each other.

Might you, kind sir, help me with this problem of mine?
The Real Elliot (author)  hellstudios3 years ago
So the only trick with (traditional, analog) servos is that they need a 1.5-2.5ms pulse every 20ms. The length of the pulse determines where they turn. You just make the pulse train with the micro and you're done!

Good luck.

hmm, do you mean through the signal wire?

you probably mean the signal wire.
Yes, you provide 5v to the red wire, ground to the black wire, and the signal to the signal wire.

On the signal wire you provide anywhere from a 1-2ms pulse of 5v every 20 ms. 1ms and 2ms make the servo move to its limits, 1.5ms centers the servo, and everything in between moves the servo everywhere in between. Good luck. :)
Great project but is the Code in C or C++? I'm an Arduinophyte. Sorry, I'm not the most hardworking person...

Once again, Great Project
Veve Tech3 years ago
When I heard Servo, I was hoping for Tom Servo lol
alterator3 years ago
glue some rubber stuff on the ends of legs, so it doesn´t slip..
pokeroz4 years ago
Is this The right setup for the brains
salahaddam5 years ago
 They had one like this at
amando966 years ago
oh and ermmm, could i make this using 555's??? i think i might be able to make a simpler one... hmmm
andy amando966 years ago
Using a Hex inverter is a good trick, 555's would be capable but not very elegant. I strongly advise you look into using a 74xx240 type chip (replace xx with ac, hc or htc (different tolerances - they should all do the job though)), there are plenty of tutorials and the components needed are minimal. The circuit type you need is typically referred to as a bicore(or bi-core) and there are tutorials showing how to solder these up without breadboards/circuit boards. Don't be scared off by different chips or schematics, best way to do. Hope this helps, Drew
amando96 andy6 years ago
ya defenantly helped, although i just bought an Arduino... lol
andy andy6 years ago
Sorry for two comments, but I just noticed, if you want simplicity try the One Motor Walker on this site, here's a link to the free-form tutorial for its control system, it links to the one motor walker tutorial.
Hope this helps,
amando966 years ago
whats is the code for an arduino? is it the same as that one?
kasman6 years ago
can u give me the schematic circuit please.. hanif,malaysia
DieCastoms6 years ago
Based solely on this 'ible, I built a 4 legged walker. Instead of the plastic substrate, I used bent and formed coat hanger wire, and instead of the atmega, I used a Futaba 4 channel RC receiver and battery pack. During the construction (which only took a half hour) I worried about whether or not I could control it manually in a manner to make it walk. I worried about having enough timing and coordination to manually control both servos. As it turns out, however, by putting both servos on the same stick (mind you NOT the same channel), spinning the stick in a counterclockwise direction produced forward (RAPID) movement, and spinning the stick in a clockwise direction produced backward (extremely unstable) movement. I am impressed with how simple this project turned out to be and how easily I was able to get good results, and I thank you for posting the 'ible. Mike, from DC.
so you just used the RC sistem? no additional circuits? cool :)
I used two servos, the RC battery pack, the RC receiver, and coat hanger wire. NOTHING else went into the construction of the robot. I have made several different .... contraptions in which to use my RC system and servos, including several different "Sumo" bots with varying size tires and construction materials, and the walker. Eventually I will post the videos on YouTube under DieCastoms. Take a look. Mike, from DC.
iw286 years ago
how do I make the ic the chip ore the brain to the walker
amando966 years ago
hey i just built this! But i put the whole thing inside a cardboard tube, and the PIC i used is 6' tall 140 pounds... :P
amando966 years ago
u can make it climb higher buy putting wider legs... :)
and ermmm where did you get the brain?
iw286 years ago
hey i just want to ask to how to make the brain to the 2 motor walker
Mike0601876 years ago
hi, can you pleas send me a clear picture or diagram of the circuit of the bot? thanks
619rey7 years ago
WHERE DO I GET Drilled project board for the circuit Snap-off headers (male and female) for the servo and battery connections???????
Derin 619rey6 years ago
rat shack may have them,but try digikey
619rey7 years ago
Derin 619rey6 years ago
the ground bus is a bus that travels on the ground,just joking read real explanation below The + bus carries the power and is similar to the positive of a battery. The ground bus is the exact opposite
robotkid2496 years ago
Can you please post the code to use with the atmega168?
Ankush6 years ago
plz give a cleam picture of the brain of this instructible
hey i am making my firsy bot can i use "futobo 3003" istead of "Ts-53" as i am having futobo with me i don't have to spend my cash on buying ts-53
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