As the name indicates, SLIM-BOT, is a small, simple, compact robot, which may be moved or controlled using various inputs, without using any micro-controller. There is no need of programming language or coding to make and control the Slim-Bot. This is the basic project for those, who don’t have any knowledge in micro-controllers and programming. The various controls for the Slim-Bot is completely based on the electronic circuits only.
Now, the Slim-Bot may be controlled wirelessly using a Joystick. A joystick has a knob to control in all the four directions (Up-Down-Right-Left), which is easy for manoeuvering the Slim-Bot. As the joystick generates analog values, op-amps are used for conversion of analog to digital values. Then the digital values are fed to Encoder IC and then transmitted wirelessly using RF transmitter.
The serial data is received by the RF receiver, sends to Decoder IC (HT12D). The Decoder IC, decodes the received serial data, back in to 4 bit data. The 4 bit data is used to control the movement of the Slim-Bot.
About Joystick ADC :
The joystick used here is normally available in the market as joystick module. Generally, this joystick module contains, three outputs, viz., dx, dy and SW.
The dx and dy are connected to mid-pins of two variable resistors, perpendicular to each other. When the knob is moved horizontally(left-right), the resistance value in dx varies. Similarly, when the knob is moved vertically(up-down), the resistance value in dy varies. So, when the joystick module is connected to 5VDC power supply (between the Vcc and ground pins), the dx and dy values are set at 2.5VDC approximately, by default. When the knob is moved left and right or up and down, the voltage at dx and dy varies accordingly. The SW pin is connected to a button switch below the knob and gets activated (switched on), when the knob is pressed down.
Hence, the output of dx and dy are analog voltages, which varies in between 0V to 5V (up to Vcc). To convert the analog to digital voltage, 4 numbers of OP-AMPs are used here. So, 2 numbers of LM358 dual op-amp ICs are used to convert dx and dy analog values, to four digital values, as shown in the circuit below.
About Joystick TX and RX:
The digital values are fed to Encoder IC (HT12E), as explained earlier in Keypad control system. Then, the digital code is encoded by the Encoder IC (HT12E) and outputs the code in serial format. Then the serial output of the encoder is transmitted by an RF transmitter. The connections between digital outputs from op-amps to Encoder IC, HT12E, are shown at the bottom of the page.
There is NO CHANGE in Receiver Board or Slim-Bot, w.r.t. Keypad control. Once the Transmitter module is ready, then switch ON the power supply to Transmitter and Slim-Bot, for easy control of Slim-Bot using joystick.