Technical Part 1 : Speed Control

Circuit diagram of voltage regulator, 7805

Due to the input valtage to PIC 16F 877A must be 5 V, therefore a voltage regulator 7805 is used to convert the 12 V power supply to 5 V and supply the voltage to the PIC 16F 877A. From circuit above the two capacitors 100uF are connected with 12V - ground and 5 V - ground, they are used to stabilised the voltage from power supply. However, the real theory to calculte the value of capicators should be used still in process. A diode-Led is used in the circuit above to indicate the 12 V sucessfully converted to 5 V when the Led is light on. The 5-v voltage cannot be supply directly to LED, it will damage the LED. So a resistor 330 ohm is used to drop the voltage and it can be calculated by ohm law.

Circuit diagram for speed control

PIC16F 877A

First , the PIC 16F 877A will be discussed. To activate PIC 16F 877A, 7 pin must be compulsory to be connected. Pin 1 which is master clear, a 4.7 K ohm which is as a pull out resistor. However the value of the pull out resistor chosen depend on the input impedance of microcontroller. We still on the process to find out the calculation for this. Pin 11, pin 32 are connected to 5 V supply and pin 12, pin 31 are connected to ground. Next, pin 13 and pin 14 must connect to an oscillator. The function of oscillator is giving the clock to microcontroller. We chose 20MHz oscillator for PIC16F877A. However, if your design does not need the so fast speed, you can use lower value of oscillator. It will help you to save the power. We still find how to calculate this.

Speed control

Due to microcontroller work in analogoues 0 and 5 V. It is impossible to use that for speed control. The better way is used the digital method to control the speed for stepper motor. As a result the first thing we need to do is change the analogoues to digital of microcontroller. To varied the digital value, a potential meter is needed which connected in pin2 as shown at circuit diagram above. The 8 led at pin 33 to pin 40 is a testing method to let us know the digital value after we adjust the potential meter.

Setup for ADC

Programming for speed control

Job distribution

Our project design is most of part in writing programming and hardware constructing. So we want to make sure every of our team members know how to write te programming. So we divide the job one part by one part to our team and give everybody a chance to learn the programming. Job distribution as shown below :

Wong Jih Kian : Speed control
Goai Teck Liang: Radio Frequency
Faizal: Motor Driver
Tamil : Encoder
Nabilah : LCD screen

After our team member knows how to write the programming for their own parts, we will combine everything together.

Things that we purchsed

Due to lack experience in microcontroller, and newbie in project design. Most of the devices we buy from shops rather to construst and build. We are mainly focusing on writing programming and learn how maximase to use those devices we buy.

Unipolar Steppr motor

Photo above shows a unipolar stepper motor that my team will use it. It is bought from cytron tecnology and cost us RM 50. We chose unipolar stepper motor for our project design because it is more easy to use it compare to bipolar stepper motor.

Motor Driver

Due to lack experience in designing the motor driver of stepper motor, we plan to buy this motor driver from cyton tecknolgy. We will discuss in details and advantages in future post. The motor driver cost us RM 135.

Encoder

Photo above shown an encoder. We are quite regret to buy this encoder. This is because we can easily build my our own. Furthermore, this encoder didnt provide the output shaft for us. So it make difficulty for us to construct a output shaft for it. It is very expensive , RM 60.

Radio Frequency (transmitters and receivers)

Photo above shows 2 set of different frequencies of radio frequency, 315 MHz and 415MHz. Due to we want to communicate in bi-directional between car and remote control that we already discussed in previous post. Therefore, 2 set of transmitters and receivers are needed.

Microcontroller (PIC 18 F 877A)

Photo above shows the 40 pin microcontroller that provided by the school. We need to learn it start from zero.

LCD display

Photo above shows the LCD display that we purchase from cytron. It is a cheaper LCD display. Again we need to learn how to write the programning for this LCD display. We will use this LCD screen to display the speed as well as the torque for stepper motor.

Estimated budget for our product

Budgets are difficult but essential tools for project management. They permit teams to identify the financial and other resources required, and to match those requirements to the available resources. Budgets also require teams to account for project monies. Finally, budgets serve to formalize the support of the larger organization from which is drawn. Design project budgets normally include research expenses, materials for prototypes and support expenses related to the project. The table below is showing our estimated budgets:

Please click the photo to enlarge it

Estimated budget