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Chapter: Microprocessor and Microcontroller - Micro Controller Programming & Applications

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Washing Machine Control Interfacing with 8051 Micro Controller

The I/O can be configured as input pin or output pin bit-ly. It is up to you to choose the I/O pin number goes to what function, but it infect the program firmware of course.

Washing Machine Control

 

Many washing m/c shell in the market has mechanical controlled sequence for activated the timer and the sequence back and forth for their motor; washing motor or spinning motor. Spinning motor control only has one direction only, and its simple could be changed to the discrete mechanical timer which sell on the market. But washing motor control has 2 direction for this purpose, it means to squeeze the clothes, it must go to forward and then reversed. The sequence is like this:

 

ü First, go to forward direction for about a few seconds

ü Than stop, while the chamber is still rotate

ü Second, go back to reverse direction for about a few seconds

ü Than stop, while the chamber is still rotate

ü And so on, back and forth, until the the timer elapsed

 

1 Schematic

 

Timing sequence like the above description, can be implemented with many way, by using discrete electronic components, timer, using a program or a microcontroller or microprocessor, etc. Because I am learning the PIC microcontroller for right now, I will implement this function using this microcontroller, but for you who familiar with another kind of microcontroller my adapted it to your purpose. By using PIC micro, it can be made more compact. First I plan to make 2 buttons, 1 for set the timer and another for reset the timer or for the emergency stop push button. Then to know the timer works or not, I need a visual display.

 

For this purpose I will use 7-segmen display showing the rest of the timer. To run the motor sequence of course I need a pair of relays (power relays, about 3 Amperes output), one for forward and another for reverse option. I will use the very common family of PIC micro, ie : 16F84A, because this is the most popular type and very simples used and very much used. Also can be obtained easily in the market. But this is the medium type of PIC micro family. It has 1kByte of memory (EEPROM type) and 13 I/O pins. It can be reprogrammable thousands times. Because the I/O just only 13 pins, I used a BCD to 7-segmen chip. So it will left a few I/O pins for expanded in the future. You can omitted this chip for timing sequence purpose and save one IC price, because the I/O just exactly enough.

 

ü I/O port A-0 = SET push button

ü I/O port A-1 = RST push button

 

ü I/O port A-2 = Reserved

ü I/O port A-3 = Reserved

ü I/O port A-4 = Reserved

ü I/O port B-0 = Forward Relay (Run motor forward)

ü I/O port B-1 = Reverse Relay (Run motor reverse)

ü I/O port B-2 = Activated unit 7-segmen (multiplexed)

ü I/O port B-3 = Activated ten 7-segmen (multiplexed)

ü I/O port B-4 = BCD data A (for 7-segmen)

ü I/O port B-5 = BCD data B (for 7-segmen)

ü I/O port B-6 = BCD data C (for 7-segmen)

ü I/O port B-7 = BCD data D (for 7-segmen)

ü Also integrated power supply to run it modularly

 

The I/O can be configured as input pin or output pin bit-ly. It is up to you to choose the I/O pin number goes to what function, but it infect the program firmware of course. Once you choose, then it is just like that, except you also change both, the program and the hardware.

 

2 Working of Washing Machine

 

The direction of rotation can be controlled when switchS1 is in position A, coil L1 of the motor receives the current directly, whereas coil L2 receives the current with a phase shift due to capacitor C. So the rotor rotates in clockwise direction (see Fig. 2(a)). When switch S1 is in position B, the reverse happens and the rotor rotates in anti-clock wise direction Thus switch S1 can change the rotation direction. The motor cannot be reversed instantly. It needs a brief pause between switching directions, or else it may get damaged. For this purpose, another spin direction control timer (IC2) is employed. It is realised with an IC 555. This timer gives an alternate „on‟ and „off‟ time duration of 10 seconds and 3 seconds, respectively. So after every l0 seconds of running (either in clockwise or anti clockwise direction), the motor stops for a brief duration of 3 seconds. The values of R3 and R4 are calculated accordingly. The master timer is realised with monostable IC555 (IC1) and its „on‟ time is decided by the resistance of 1-mega- ohm potmeter VR. A 47-kilo-ohm resistor is added in series so that even when the VR knob is in zero resistance position, the net series resistance is not zero





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