Let's Make Robots!

Arduino Robot - Biped


This bipedal robot is built as cheaply as possible. Hence there are no sensors, fancy servos or brackets.

Height of robot: 20cm
Weight of frame: 150g
Weight of batteries: 210g

Microcontroller: Arduino Duemilanove
Power supply: 6xAA batteries (7.8V)
Servos: 6x r/c micro servos (HXT900)

Main Building Materials: ice-cream sticks, brass eyelets, hot glue, corrugated plastic board.


Brief Description:
Basically the ice-cream sticks are used to replace normal servo brackets and hot glue is used instead of screws. Lots of hot glue.

Drill a hole at the end of two ice-cream sticks and connect them with the brass eyelet.. and you got yourself a simple hinge!

You need to calibrate each servo horn angle before tightening its screw to the servo. In other words, when at zero angle, the left and right servos should match up about the same. Best way to do this is through stubborn trial and error!

I used HXT900 servos because of their price and reliability. One tip is to remove the labels before applying hot glue as labels generally lose their stickiness overtime. It sucks when the robot comes apart not because of glue or parts failure but stickers peeling off! Also, apply the hot glue generously and always reinforce the sides! But make sure there is proper ventilation in the room if not you will bound to get a headache.

As you can see, the batteries make up about 60% of the total weight. Im thinking of switching to those lithium batteries as they have better power to weight density.. and i might even be able to add a few more servos and reduce the jerkiness of the way the bot walks.

So please email me at lazymanacc@gmail.com and support this site! Check back at http://retardokiddo.blogspot.com/ regularly for new updates!

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nice! kudos

Good job! It`s interesting seeing people push cheap micro servos to achieve as much as possible on a budget. Is there any sign those servos are really stressed?

Looking forward to more improvements in code!

oh yes they are, due to the weight of the batteries and CG, and yes too.. they are really cheap!

Biped usually heavy and need powerful servos to support their weight but you made it happens!! Cheaper servo could walk too!!

Really nice project whipped together with Popsicle sticks - Frits would be proud..

The slick floor seems to help it moon-walk..  I was waiting for it to bust a few moves though.. Can you do a deep knee-bend, flip and spin on head, breakdance sort of thing?

haha anything is possible.. but i already have other plans for my next project.. the acrobatics will have to wait... lolx

This looks cool. I want to build something similiar. Do you mind sharing your code? it will give me a pretty nice guide on writing one to fit the bot that I build.

hi elijah, i did this so long ago that i already lost the code, even the robot itself is already dismantled and cannibalised for other projects. There really is nothing much to it, no fancy mathematics to this one except trial and error. Just go to the arduino website and look at the code for making a servo move. After that put the robot together and manually move the servos with your hand, simulating the way it should move. If i remember correctly it should consist of these phases

1) shift weight of the robot to one leg

2) lift up the other leg without the robot tipping over

3) place the leg up in the air one step in front of the robot

4) repeat the whole thing again

Once you get a rough idea of how you want to make these happen (depending on how u arrange your servos) just estimate and take down the individual servo angles required to make it possible. It will probably take some fine tuning before you get the balance and coordination required. If im not wrong, in the arduino code its just a bunch of servowrite functions in the loop()

hope this helps


Ok thanks!

What type of servo controller did you use?

no servo controller.. just connect the servos to a common supply/ground, then their signal wires directly to the pwm pins of the arduino board..

now that you mentioned.. what advantages do servo controllers provide? i always wanted know..