Week6

Etching Process

Week 5

PIC Fan controller

This project it´s based on a PIC16F877A, with the purpose of control a FAN with PWM (Pulse with Modulation). It offers a variable speed control, low acoustic noise, reliability, long lifetime, low power consumption, protection features. The MCU get the temperature from the sensor (D18B20), and after will do a conversion Celsius degrees and then it´s generated a PWM on PORTC.2 with 6 different levels.

PWM	TEMPERATURE
15%	<= 49°
30%	50°
40%	51°
50%	52°
75%	53°
100%	>54°

After the signal goes to Q1 (BC338) in order to control the duty cycle in the fan. I had to use two transistors to have an Ic on Q2 to be enough to activate the fan. Because the MCU only generate a maxim of 3.6V on which output, and 15% of 3.6V is 0.5V to polarize Q1 we need 0.7V.

How to calculate the Q1 and Q2:

You will be able to control the FAN between 5V and +/-12V.The BC338 have a current load of 800mA that is value of a fan can have, you can use two or more fans as long the current load isn´t more than 800mA. The output of MCU connect to the Q1 and Q2 it works like a switch, the D3 it´s for protection from the magnetic field in the inductors from the FAN, without the D3 when you turn off the system the current will be discharge to the Q2 and could damage it. 

Connectors
J1	Expansions PORTS
Source	12V
Sensor	D18B20
FAN	Connect the FAN
ICSP	To program with PICKIT2

Pictures:

 

 

Link

Week 4

IR Receiver

IR Receiver

This is a simple IR receiver circuit which plugs into a serial port of a computer. There are many other circuits of this kind, and most of them are even simpler, but this circuit has two major advantages: 

(1) it uses an Atmel AVR RISC microcontroller (an AT90S2313) instead of the usual PIC microcontroller

(2) it uses a Maxim MAX232 for the generation of valid RS232 levels.

Advantage 1: is, of course, only valid for all those AVR addicts which have this device (and the corresponding programmer) ready at hand and don't care about PICs and PIC programmers. 

Advantage 2: comes into play if the IR receiver has to placed at a great distance from the computer. The MAX232 is more likely to deliver valid signals over bigger distances than cheaper solutions.

The IR receiver can receive it's +5V supply voltage from the keyboard or mouse connector of the computer (either from an unused PS/2 port or via a pass-thru adapter). If the IR interface is placed at a great distance from the computer, I power it with an external stabilized 5V DC power supply instead of the PS/2 port.

The interface communicates at 19200 baud, unidirectional (that means, it only transmits data and does not care anything about data which the computer send), without flow control. For every level transition in the demodulated IR signal, it transmits a single byte which corresponds to the time since the previous transition, capping off at a value of 255. It works reliable with a Sony remote control (using the special Sony protocol), and I have also successfully tested it with an Onkyo remote control (I think this one uses the standard RC5 protocol, but I'm not sure). Decoding happens on the computer; I use PC Remote Control for this.

 

Appendix:

Infrared Receiver

Infrared Receiver to RF Transmitter Circuit

IR receiver sensor

 

 

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Week 3

Electric Gearbox Motor 12v

Motors need to be isolated from the AVR.  This is because they produce a high voltage spike when the current flow through them suddenly changes. This can damage the digital circuitry in the microcontroller. To separate the Gear-Box Motor from the microcontroller we used 4N35 optoisolators. Furthermore, ULN2003 drivers are used to supply the motor's high current needs since the microcontroller has a maximum current rating of 40mA. The drivers contain diodes to protect the circuitry from high voltage spikes by directing the current through the power supply.

The motor is controlled using an 8-step sequence to halve the rated step angle. The step sequence rate is controlled via software. The 8 step sequence not only slows down the motor but also allows more accurate positioning of the platform.

Specifications:

Electric gearbox motor, Speed reducer motor, Gear transmission motor 

1) Diameter :37mm shaft: 6mm
2) 12v Custom made speed, Torque etc

  

 

Assembling DC motor:(diameterxlength=35.8x57.0mm)

Geared motor installation:

Appendix: 

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