Hand Motion Controlled Robotic Arm

This system allows controlling a robotic arm by hand movements. This system uses RF receiver which is interfaced to the 8051 microcontroller which controls the driver IC which is responsible to control the movement of the arm. The transmitter circuit consists of an accelerometer sensor which is interfaced to the Atmega microcontroller.

The transmitter circuit sends commands to the receiver circuit. This commands indicates whether to move the robotic arm in upward or downward direction or whether the commands indicates to grip an object or release it.

Hardware Specifications

• 8051 series Microcontroller
• Accelerometer
• Diode
• RF module
• Encoder
• Decoder
• Atmega 328 Microcontroller
• Motor driver IC
• DC motors
• Batteries

Software Specifications

• Arduino compiler
• Keil Compiler for 8051 MC
• MC Programming Language: Embedded C

Accelerometers

What’s an accelerometer measure? Well, acceleration. You know…how fast something is speeding up or slowing down. You’ll see acceleration displayed either in units of meters per second squared (m/s²), or G-force (g), which is about 9.8m/s² (the exact value depends on your elevation and the mass of the planet you’re on).

Accelerometers are used to sense both static (e.g. gravity) and dynamic (e.g. sudden starts/stops) acceleration. One of the more widely used applications for accelerometers is tilt-sensing. Because they are affected by the acceleration of gravity, an accelerometer can tell you how it’s oriented with respect to the Earth’s surface. For example, Apple’s iPhone has an accelerometer, which lets it know whether it’s being held in portrait or landscape mode. An accelerometer can also be used to sense motion. For instance, an accelerometer in Nintendo’s Wii-mote can be used to sense emulated forehands and backhands of a tennis racket, or rolls of a bowling ball. Finally, an accelerometer can also be used to sense if a device is in a state of free fall. This feature is implemented in several hard drives: if a drop is sensed, the hard drive is quickly switched off to protect against data loss.

Now that you know what they do, let’s consider what characteristics you should be looking for when selecting your accelerometer:

• Range - The upper and lower limits of what the accelerometer can measure is also known as its range. In most cases, a smaller full-scale range means a more sensitive output; so you can get a more precise reading out of an accelerometer with a low full-scale range. 
  You want to select a sensing range that will best fit your project, if your project will only be subjected to accelerations between +2g and -2g, a ±250g-ranged accelerometer won’t give you much, if any, precision. 
  We have a good assortment of accelerometers, with maximum ranges stretching from ±1g to ±250g. Most of our accelerometers are set to a hard maximum/minimum range, however some of the fancier accelerometers feature selectable ranges.
• Interface - This is another one of the more important specifications. Accelerometers will have either an analog, pulse-width modulated (PWM), or digital interface.
• Accelerometers with an analog output will produce a voltage that is directly proportional to the sensed acceleration. At 0g, the analog output will usually reside at about the middle of the supplied voltage (e.g. 1.65V for a 3.3V sensor). Generally this interface is the easiest to work with, as analog-to-digital converters (ADCs) are implemented in most microcontrollers.
• Accelerometers with a PWM interface will produce a square wave with a fixed frequency, but the duty cycle of the pulse will vary with the sensed acceleration. These are pretty rare; we’ve only got one in our catalog.
• Digital accelerometers usually feature a serial interface be it SPI or I²C. Depending on your experience, these may be the most difficult to get integrated with your microcontroller. That said, digital accelerometers are popular because they usually have more features, and are less susceptible to noise than their analog counterparts.
• Number of axes measured - This one’s very straightforward: out of the three axes possible (x, y, and z), how many can the accelerometer sense? Three-axis accelerometers are usually the way to go; they are the most common and they are really no more expensive than equivalently sensitive one or two axis accelerometers.
• Power Usage - If your project is battery powered, you might want to consider how much power the accelerometer will consume. The required current consumption will usually be in the 100s of µA range. Some sensors also feature sleep functionality to conserve energy when the accelerometer isn’t needed.
• Bonus Features - Many more recently developed accelerometers may have a few nifty features, beyond just producing acceleration data. These newer accelerometers may include features like selectable measurement ranges, sleep control, 0-g detection, and tap sensing.

ATmega328

The Atmel 8-bit AVR RISC-based microcontroller combines 32 KB ISP flash memory with read-while-write capabilities, 1 KB EEPROM, 2 KB SRAM, 23 general purpose I/O lines, 32 general purpose working registers, three flexible timer/counters with compare modes, internal and external interrupts, serial programmable USART, a byte-oriented 2-wire serial interface, SPI serial port, 6-channel 10-bit A/D converter (8-channels in TQFP and QFN/MLF packages), programmable watchdog timer with internal oscillator, and five software selectable power saving modes. The device operates between 1.8-5.5 volts. The device achieves throughputs approaching 1 MIPS per MHz.

Features

Ø  High Performance, Low Power AVR® 8-Bit Microcontroller

– Advanced RISC Architecture

– 131 Powerful Instructions

– Most Single Clock Cycle Execution

– 32 x 8 General Purpose Working Registers

– Fully Static Operation

– Up to 20 MIPS Throughput at 20 MHz

– On-chip 2-cycle Multiplier

Ø  Flash Program Memory: 32 kbytes

Ø  EEPROM Data Memory: 1 kbytes

Ø  SRAM Data Memory: 2 kbytes

Ø  I/O Pins: 23

Ø  Timers: Two 8-bit / One 16-bit

Ø  A/D Converter: 10-bit Six Channel

Ø  PWM: Six Channels

Ø  RTC: Yes with Separate Oscillator

Ø  MSSP: SPI and I²C Master and Slave Support

Ø  USART: Yes

Ø  External Oscillator: up to 20MHz

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