First Place on Indonesia Intelligent Robot Contest 2004 (legged category)
Best Innovation on Indonesia Intelligent Robot Contest 2004 (all category)
Balairung Kampus Universitas Indonesia
Depok July, 10th-11th, 2004

What is Arachnid?
Arachnid is a class name of animal (arachnida) who has 4 pairs of legs, breath at an open air for oxygen, has simple two or more eyes, but doesn't have wings like insect. The way they eat is sucking liquid and also inject a small amount of "disgestive liquid" to their prey to melt hard tissue become liquid. Anthropod that classify as Arachida are spiders, scorpions, and crabs. Arachnid is not insect because insect has only 6 legs.

Arachnid the robot is made similar in shape as arachnida has but the number of leg reduce into two pairs. The segmentation of the body also not completely show where the head is, the body, or the tail. Some limitation must be made here in order to make the movement more flexible and the robot itself can be programmed easily. This Arachnid can be program to walk like a spider, a crab, or a scorpion by simply change the walking routine program in the program memory of microcontroller.

Arachnid Team
Arachnid is invented and well design by a team which consist of a lecturer (it's me) as instructor and 2 students as a team leader and a member. They are Ekawahyu Susilo, Maryanto, and Anton Mutiara. The aim of team was made is participating in Indonesia Intelligent Robot Contest 2004, Fire Fighting Robot, legged category.

Arachnid and Indonesia Intelligent Robot Contest 2004
Indonesia Robot Contest has been held to show capability and creativity of regional students every year and Indonesia Intelligent Robot Contest was held for the first time in 2004 in addition of Indonesia Robot Contest 2004 event. IIRC2004 held by Direktorat Jendral Pendidikan Tinggi whiches adopt original rules of Trinity College Fire Fighting Robot Contest, USA. This rules cover the limitation of dimension, game field design that part into four rooms, size of candle, penalty score if the robot touch or scratch walls, minimum range to put out the candle, etc. Base on that rules, we design Arachnid to hear a fire alarm at about 3.5kHz, automaticaly search for a lit candle in rooms, put it out, and back to home base soon. Along traveling, Arachnid senses walls from 15-20cm distance so it might not touch or scratch walls.

Two categories in IIRC2004 are wheeled robot and legged robot, competed for a chance to fight internationaly on April 2005 at Trinity College. EVO-113 from Politeknik Bandung get a first place in IIRC2004, wheeled category, while Arachnid win a fisrt place in legged category and also have an honor as The Best Innovation Robot for all category.

Microcontroller
Intelligent, always build by an algorithm, that lay inside of microcontroller. The type of microcontroller of Arachnid compatible with MCS51 family, AT89S51. This type of microcontroller is very cheap and powerfull in any industrial application. The letter 'S' in the middle of the it's type show that this controller facilitate In System Programmable (ISP) program memory. Can be programmed inside the mainboard.

Motor R/C Servo
As the actuator and the body shape, 12 pieces of R/C Servo, constructed as a main structure of Arachnid. Those servos are divide into 4 legs, so each leg is able to move in 3 degree of freedom (3 DOF). We use HITEC HS-322HD which operate at 5 volt dc on 3 kg of torque.

Infrared Range Sensor
To avoid collision and obstacles (including walls), range sensor are needed to measure range between the robot and obstacles. The range are variable and should be setup initialy in the range from 10 mm to 200 mm. Arachnid use 5 range sensor, front, back, left, right, and bottom to compare white and black color on the floor.

Fire Sensor
Fire can be detected it presence using two ways, the light and the temperature. More specific , the light itself classify as infrared light. IR-photodiode is one of the sensor that fit our need. While searching for a lit candle, Arachnid scan every room 180 degree in front of and capture range 60 cm radial.

Another option to detect a lit candle is using UVTron, specific fire's ultraviolet sensor. So, in spite of infrared sensor, Arachnid also armed with ultraviolet sensor.

Sound Activation
Another challanging topic that given in the contest is an extra score if the robot can "hear" the fire alarm and start automaticaly to find fire in rooms. The fire alarm itself has to be a generic one that may have spectrum between 3kHz to 4kHz. We decide to detect the midlle frequency and spread the bandwith over 1kHz. So, all spectrum are well covered. Electret Condenser Microphone (ECM) is the basic component to hear this alarm but the signal still too weak. We need a small signal amplifier using transistor and a tone decoder LM567.

Extinguisher
In order to extinguish the fire (represent by a lit candle), Arachnid carry a small dc motor plus a very aerodynamic slim propeller (especialy design for aeromodeling plane). This extinguisher is controlled directly by microcontroller using the right program and algorithm to earn high speed of blown air.

Arachnid The Book
We currently wirte a book of Arachnid. Soon we will publish it. All source code and complete patern of designing this robot will be given freely on this website. Hopefully worth to future establishment in robotics, particularly among creators.