Introduction: How to Freeform the Bicore ( BEAM Robotics )

This instructable is part of the one motor walker.

The bicore or suspended bicore is the name given to a little circuit created by Mark Tilden. He is the founder of BEAM robotics. BEAM robotics is an acronym for Biology, Electronics, Aesthetics, and Mechanics.

quote from Wiki

"Probably the most utilized Nv Net topology in BEAM, the Bicore consists of two neurons placed in a loop that alternates current to the output. Input into the loop is given in the form of changing the resistance in each separate Neuron, which changes the rate at which the Neuron discharges, affecting the pace at which the loop oscilates."

WOW my head! Let me reformulate that for you.

The bicore is a oscillating circuit. In our case, it will oscillate a motor, like the wiper on your car.
The motor will go back and forth, back and forth when power is apply.

Look at this video to understand:

This instructable was a Flash animation for my BEAM website. You simply follow these instructions.

Step 1: The Bicore Freeform

Many thanks to Ian Bernstein from

Step 2: How to Freeform the Bicore ( BEAM Robotics )

the parts

I recommend the 74AC240

the AC version.

It give more power for the motor.

The resistor in this circuit will change the oscillation. Bigger resitor make the oscillation long.
You see both (R)

it equals to this


You connect the resistor between the tow (R)
From pin2 to pin17

You will find all these part at

They have everything and there are very friendly!

Step 3: How to Freeform the Bicore ( BEAM Robotics )

Step 4: How to Freeform the Bicore ( BEAM Robotics )

Step 5: How to Freeform the Bicore ( BEAM Robotics )

Step 6: How to Freeform the Bicore ( BEAM Robotics )

Step 7: How to Freeform the Bicore ( BEAM Robotics )

Step 8: How to Freeform the Bicore ( BEAM Robotics )

Step 9: How to Freeform the Bicore ( BEAM Robotics )

Step 10: How to Freeform the Bicore ( BEAM Robotics )

Step 11: How to Freeform the Bicore ( BEAM Robotics )

Step 12: How to Freeform the Bicore ( BEAM Robotics )


GreeceFallout made it!(author)2014-12-12

100% nothings wrong checked it many times

GreeceFallout made it!(author)2014-08-20

I Have followed the steps one by one and managed to make it BUT , when i connect it to 5v all i can see is that my motor is vibrating like crazy and after measuring the voltage across the motor i discovered it was less than a volt.....

I Used the 74HC240 , With the 22nF Capacitors and a 1/4 100k resistor , my motor is a dc one from a cd player . . . . I Am utterly confused, any help please ?

robomaniac made it!(author)2014-08-20

oh boy oh boy! It's been a very long time I did not touch a bicore!

are you sure those are 22nF?
are you sure that is a 100k resistor?
is the motor able to spin easilly with a 5V battery?

If you change from 100k to 1Meg resistor, this will tell how long it turn on one side then the other side. On a servo motor it turn clockwise for 1/2 a second and anti clockwire for 1/2 second

if you have a small resistor, that mean that it would oscillate really fast..
maybe that is why you hear the vibration but it might just be the motor spinning clockwire then anti clockwire REALLY fast.

try a different resistor,

measuting the motor voltage could and could not be usefull.
I guest that if the oscillation is slow, you might actually see for example 5Volts for 1/2 second then -5Volts for 1/2 seconds.

if that does not work, disconnect everything and star again.
try on breaboard. try other small motor.

oh yeah... the HC240 is not that powerfull... you need the AC that can provide more current per pins. Yeah HC = 35mA per output

the AC = 75mA

you have 3 buffer/output on the bicore, that mean
35mA * 3 = 105mA
75mA * 3 = 225mA

Now it depends on how much current your motor is. If it's brand new and not recycle it can be low, under 100mA otherwise if it's more then it could not work since the chip will protect itself or fail.

good luck!

GreeceFallout made it!(author)2014-12-12

Well , I don't know I am starting to feel dumb , I made the whole thing again only to get the same humming motor , the difference is when I push the motor it starts moving indefinitely to one direction , for the love of god I can't find a AC version

GreeceFallout made it!(author)2014-08-21

Thanks for your fast response , you provided me with all the stuff I should know, Appreciated ! :)

MCRIPPPer made it!(author)2011-06-17

hi. im wondering if the capacitor value is essential? can i use a 0.1 microfarad ceramic cap instead of 0.22??

lukeD made it!(author)2011-06-05

no programming or software?

saqrock made it!(author)2011-04-21

If i am using a 9v battery which Chip should I use instead of 74AC240.

101nemesis made it!(author)2011-02-02

hey guys.
i got the ic 74hct240.
What i was wondering is that does this ic require any sort of programming or is it pre programed..

yogesh99 made it!(author)2010-09-28

Hello Sir, Can I use 'SN74LS240N' instead of 74HCT240. I am unable get this IC . Please tell sir,I really want to do this project. Also is their any application of '74HC14B1' IC in BEAM Robotics.

PrathameshKini made it!(author)2010-09-11

Why is pin number 16 connected to pin number 17?!

robomaniac made it!(author)2010-09-12

you got it wrong, that is pin 3 and 4, the chip is upside down. It connected like that because that is the way to make the bicore work. Look up the schematic of the bicore.

PrathameshKini made it!(author)2010-09-10

I have constructed the bicore circuit. Now I have modify the servo. However I want to know why the servo was chosen over a simple DC motor. And what is the drive current and the sink current of the circuit?

robomaniac made it!(author)2010-09-10

simple DC motor does not have a gear box, that mean no power to make the robot walk. Each inverter from the smith trigger can deliver 24mA. I think we have 3 gates so that mean 72mA for one direction, then 72mA for the other direction. A total of 144mA . That is the 74AC240 chip from fairchild. It could change depending of the manufacturer.

PrathameshKini made it!(author)2010-09-11

I don't understand. So what if it doesn't have a gearbox. Can I not just glue a circular piece of plastic to the shaft of the motor which will do the same thing as the servo horn and then glue the gear which has been cut in half to that plastic piece?
Also, if I'm using the servo I don't have to remove the plastic tab right? And is 6V input to the terminal okay? Because it says 5V in the bicore tutorial.

aviksaras made it!(author)2010-07-04

I have made my BICORE.But it is not working.Does the difference in motor cause that.I live in India so can be?the poblem is-it's taking only one round and stoping,don't know why?I have a 9V battery so can that be the problem.i have many questions to ask so please don't be annoid.Please.

mattyh made it!(author)2010-07-17

Hello, I believe the 74AC240 can only handle 6v max so chances are you've blown the chip. With my playing around with freeforming ive found it usefull to freeform an IC holder as that way any damaged ICs can easily be replaced.

robomaniac made it!(author)2010-07-17 page 2 absolute max rating is 7V, the recommended is 2 to 6V

aviksaras made it!(author)2010-07-04

Hello again,Jerome i have another problem-i have a resistor of some other colour so that could be the prob?only two colours are matching.

salahaddam made it!(author)2010-01-09

 Hey I bought a cool BEAM robot like this at

mohankarthik made it!(author)2009-12-09

pl help me . i ve finished making d body of d walker . m not getting d control circuit output for two days . pl help me out .

mohankarthik made it!(author)2009-12-09

hi . m not getting any rotation of shaft after i did this circuit . any suggestionms ?

cheverecachaimachochidoche made it!(author)2009-10-07

hello robomaniac,
I cant get the 74HCT240, does it have to be a particular kind of IC chip?
can you suggest me another IC chip?

robomaniac made it!(author)2009-10-07

yes it has to be a 74xx240 chip
the xx mean HCT, AC, etc.

If that was not a specific IC it would be call "theUniversalChip, you can use it everywhere" it does not exist... microcontroller can do sort of that.

There are is a lot of chip and they all do different things in life.

you can buy it online here

warpling made it!(author)2009-09-01

I've built a two motor walker before, and discovered and built yours many years back! I loved the simplicity of it, why make a master slave using two motors! Anywho I rediscovered your tut here on instructables and I have to say great graphics and I'm excited to try again. I've always wanted to try using a pager motor and cell phone lion battery (with the possibility of a solar charger as a separate project). Think it's possible?

robomaniac made it!(author)2009-09-01

If you use a pager motor, you need a gearbox. You can also use lithium battery but be sure to have the specific charger for those battery. Maxim IC have chips for USB lithium battery charging. And yes you could make a robot using those item. Have fun! Jerome

warpling made it!(author)2009-09-01

Would an internal gearing system like this be powerful enough?
Thanks again,

robomaniac made it!(author)2009-09-02

The pager size motor gear box is not enough powerful.

The second motor is perfect.

Check there

derbert made it!(author)2009-08-03

i must be getting on your nerves now, huh? take it as a compliment. does it have to be a particular kind of IC chip? i have a MAW2819.4. will this do? it's 20 pin.

robomaniac made it!(author)2009-08-03

you are not getting on my nerves.

Does it have to be a particular kind of IC chip
If I ask you this " do you think manufacturer make 1 single 20 pin chip for the entire world?" The ultimate universal chip that fits in your ipod, your cell phone, pace maker, airplane, watch, etc.

The answer is no, I could not even google the chip number you have.There are millions of chip out there and each and single one has a specific function.

So no, not all 20 pin will do.

derbert made it!(author)2009-08-03

hmmm. bugger. well, this one came from a remote control, so i'll give it a go. i'll have a look at the robot the control went with too.

derbert made it!(author)2009-08-03

if my capacitors are .22uf but are the black tube ones does THAT matter?

Ghost+Wolf made it!(author)2009-07-18

Question: Do I use a solar cell or batteries? If I do connect a solar panel to it, how do I know that I won't FRY the IC.

robomaniac made it!(author)2009-07-18

This circuit can only be powered by batteries. Connect the circuit to 5V and you will not fry it. Instead of connecting a motor, you can also plug 2 LED at the output ( where the motor was connected) to see if the circuit works. Connect the Anode to the chip and the cathode to ground. Same thing with the other LED on the other side of the chip.

Ghost+Wolf made it!(author)2009-07-18

Thank you, I just was wondering

Yashknowsbetter made it!(author)2009-04-02

Hey there is an error in the no. 17 and 16 are shown to be connected when they are actually not! In other words we are practically connecting i/p of one not gate to o/p of another...thus creating a monostable multivibrator...

m3lt made it!(author)2009-02-21

Parts list and links to purchase parts would help greatly. Presentation is great, but lack of info kills it.

robomaniac made it!(author)2009-02-22

I will take that in concideration for my next instructables, I am making soon. check out for parts, they have everything for that project. Thanks Jerome

trebuchet03 made it!(author)2008-07-15

Nice write up... Just to point out for others that may not be aware... Windshield wiper motors do not reverse directions - they spin in one direction and drive a mechanism that has the back and forth motion....

amando96 made it!(author)2009-02-21

they are so powerfull...

robomaniac made it!(author)2008-07-17


allenph79 made it!(author)2009-01-19

Hey om im a 12 year old guy and i was wondering what parts do you need for all this and can you get them cheap i am working my way up to bigger robots i started with bristle bot then almost done with your beetle bot and my next project is the walker, also i have a schematic for a robot i invented i was wondering if you could help me out with it but you dont have to thanks!

itanium made it!(author)2008-07-19

very interesting! gratz there

About This Instructable




Bio: 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 ... More »
More by robomaniac:Arduino-Fart-O-MeterNo pictures costume for Hong Kong HalloweenDead killer bee prank ( April fools )
Add instructable to: