Let's Make Robots!

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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Elijah912's picture

Ive just started working on a very similar biped. Check it out at:

http://letsmakerobots.com/node/29883

hey nice work.. in some of the comments of my robot there are suggestions to put some rubber grips on the foot for better traction.. you might wana try that too... the underside of the mousepad seems like an ideal choice.. maybe u wana find an old mousepad and cut it out.. let me know if it works if u do try.. lol..

Elijah912's picture

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

 

Elijah912's picture

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..

 

lumi's picture

I can tell you. The servo controller is nothing more than a board with a lot of pins, sometimes with an additional power supply for the servos only. On that pins you can plug the servo cable very easy since on an original Arduino board you do not have that many connectors for the power supply. You can check my own "servo controller" which does not "control" anything but provide the 3-pin connetion for the servos equipped with an heavy duty power line ;-)

http://letsmakerobots.com/node/29709

OddBots Spider controller witht the high power servo shield puts the bar higher. There is also a connector for high power supply since it's capable to drive a whole bunch more servos.

http://letsmakerobots.com/node/26054

 

Elijah912's picture

Most likely im going to need a servo controller with the amount of servos I will be using. I want do replicate this popsicle sticks and all, but add an upper body with arms as well as a ping sensor for the head and program it to walk around and and avoid things.. Seems like a fun project. The servo controller OddBot used on chopsticks looks pretty extreme.

sounds interesting!! remember to let us know when its done!

OddBot's picture

I am wondering why you appear to have the ankles tilting the wrong way? If you tilt them in the opposite direction then with some experimentation you should be able to get the robot to balance on one foot. This will allow the other leg to move more freely and make the walking gait more efficient.