The simplest way of constructing a 3 axis robotic arm.
Date: Monday, January 19 @ 23:47:56 EST
Topic: Atelye

This article is about making a robotic arm without knowing any detailed electronics, asm coding, programming a micro etc.

The system to be constructed is a simple robotic arm powered by 4 servos. The parts are cut out of 2mm plywood and servos are mounted to the parts by small screws. The arm can move on 3 axieses and also has got a gripper which operates with a servo as well.

To control this mechanical system, we need a circuitry which generates the separate pwm (pulse width modulation) signals of each servo. This circuitry can be realized in different ways; We can use a simple circuitry built around a very complex component, a microcontroller, we can use an even more component as well; The pc , via parallel port. Or we can try to design a circuitry with standart analog-digital IC's on the market.

In our application in this article, we are using a preprogrammed IC, endtas OZ-SER-1

Oz-ser-1 chip as you can see from the photo above, has got 18 pins and in DIP form. The chip generates pwm signals necessary to drive 4 servos independently. The chip can be programmed thru a small keypad and the programmed servo is shown with its consecutive LED display. A piezo buzzer generates beep signals on every program step to display it is running.

The chip doesn't need any external components to operate. Only some pullup resistors for the keypad. The circuit may work within 4-6V.

The simple circuit which is necessary to be constructed for the optimum operation of the chip.CIRCUIT SCHEMATIC

It is advisable to construct the circuitry on protoboard first and test before beginning the final assembly on multiholed prototyping board.

After soldering the components on prototyping board you may proceed to cut the pieces of the robot arm from plywood. The pieces are simple as you can see on the photo above. By using the disk shaped montage part which comes along with every purchased servo, you can screw servos to the arm pieces easily. And i've used wire pieces to mount the servobodies.

By clicking the links below, you can download two videoclips of the system described here.

Videoclip 1
Videoclip 2

After constructing the mechanical assembly, testing it by hand, you can begin testing circuitry and the mechanics all together. You can enter any motion program by using the 6 buttons on the circuitry. The program can be extended up to 32 steps and each step carries a distinct position data for EVERY servo. The program is stored at the nonvolatile memory of the chip and is repeated continuously as long as power is applied. You can use more chips, if you want to control more servos. In this article, you can read more on how to program oz-ser-1.

The chip is ideal for small animatronics, robotic statues, robotic show objects, robotic arms etc. Namely any object which is powered by 4 or more servomotors.

By using other ozz servo control chips, pc controlled robotic systems up to 8 servos etc can also be realized. Detailed info on ozz chips.

Cutting plan for the plywood pieces.
Print the plan according to the dimensions of the servomotor to match your servomotors. Then glue the paper onto the plywood plate and cut by using a plywood saw. Drill the necessary holes and assemble your gripper first by using small screws enabling the necessary moving parts slide easily. Then mount your servomotors on to the plywood pieces by using small screws and pieces of wire.. Or whatever method you like to use.

Have a nice day full of hobby robotics :)

This article comes from Robotik & Elektronik

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